shafts props and cables

Bermuda Brother · Post by **Bermuda Brother** » Jan 13th, '09, 20:50

Hi Guys,

just got a few more questions about my rebuild.

-I am installing the controversial 370 hp cummins 6bta's with the Twin Disc
gear boxes with 1.5 to 1 ratios.

First question is easy:

What shaft length do I need to order for her? I need to order these now before engines are installed so they get here (Bermuda) in time so can't measure directly.

What controll cable length do I need to order? For same reasons as above.

Also, for you guys who have done either the 330hp or 370hp install in the B31 what prop pitch and diameter would work best with my boxes?

I am sure some of you gurus have the answers.

Hear from you soon.

JJ

Ironman · Post by **Ironman** » Jan 14th, '09, 12:03

Whats this? Never heard that
((controversial 370 hp cummins 6bta's))
rather the "gold standard" ...

Ive got 330s & get 30 knots outta them turning 3000rpms got a 18000 # boat w/ a tuna tower & loaded for anything.
got ZF 220s 1.25 to 1 with a 1 3/8 shaft.. used the gasser shaft with a 18x18 prop.. was inch or two short so I added a shaft saver ..
Wayne

bob lico · Post by **bob lico** » Jan 14th, '09, 15:28

what exactly do you mean by the word " controversial " could you please explain.

CaptPatrick · Post by **CaptPatrick** » Jan 14th, '09, 16:21

bob lico wrote:what exactly do you mean by the word " controversial " could you please explain.

Controversial to me means any diesel engine above 320 hp in a B31...

dougl33 · Post by **dougl33** » Jan 14th, '09, 17:41

JJ,

I'm running 300hp 6BTA's in my 33. 1.5:1 zf 220a's, inch and 3/8's shafts, and 21x22 3 blade Mich DJX with a med (aka #5) cup. Cruise is 23-24 knots at 2400rpms. On the pins is 2900rpms and 28-29 knots depending on conditions. There are 4-6 other 33's running nearly indentical set-ups (some have 330b's), and all get the same exact results.

Since the 370's attain their higher HP by turning more revs, a similar set-up should work for you.

bob lico · Post by **bob lico** » Jan 14th, '09, 18:04

i am going to stay out of this other than to say thats the perfect engine for the boat both weight and hp.i may be wrong but then cabo 31,luhrs 30,rampage 30, and every other sportfisherman in american for 2008 in 31 has oem 350hp or more what are we chop liver?
a stock prop would be ---michigan propeller dyna jet 21"x 26pitch and # 5 cup if you are under 13,000 pounds if more drop to 25 pitch.

In Memory of Vicroy · Post by **In Memory of Vicroy** » Jan 14th, '09, 18:14

Saw a review in the new SWS of the Rampage 31 with twin Vulva IPS diesels and the speeds reported were amazing.....like low cruise of 35 kts and hi cruise of 45 kts.....these were 385s and 465s were an option. We are indeed chopped liver. Pussies actually. My B31 at 24 kts goes damn fast and a long way. I repeat the IPS is a totally stupid idea and now mercruiser has copied it to show two can be a dumb as one???

UV

CaptPatrick · Post by **CaptPatrick** » Jan 14th, '09, 18:16

i am going to stay out of this other than to say thats the perfect engine for the boat both weight and hp.i may be wrong but then cabo 31,luhrs 30,rampage 30, and every other sportfisherman in american for 2008 in 31 has oem 350hp or more what are we chop liver?

Weight: Not an issue... HP: Way too much...

Theres not enough room under the hull to swing the right props for loading of the engines. 21" diameter is really pushing it, (1 1/2" clearance), and above 23" pitch on 1.5:1 gears the idle speed will blazingly fast.

31,luhrs 30,rampage 30, and every other sportfisherman in american for 2008 in 31 has oem 350hp or more

Apples and oranges...

Carl · Post by **Carl** » Jan 14th, '09, 18:16

Bermuda Brother wrote:Hi Guys,

First question is easy:

What shaft length do I need to order for her? I need to order these now before engines are installed so they get here (Bermuda) in time so can't measure directly.

JJ

Id' think twice about doing that.

Boats shafts vary from boat to boat and even from side to side. So I would really consider waiting till the motors, gears, logs and struts are in place then take some real measurements and then have them made up.

If you where at my door with cash in hand I would tell you the same thing.

Carl

bob lico · Post by **bob lico** » Jan 14th, '09, 18:32

well capt patrick you got me on the idle speed of the boat that has to be address possibly two speed zf.when i had the fuel injection pump recalibbated and the rest of the changes the boat was at 38knt.so i adjusted the boat as straight as possible then put in reverse.easy to talk about now but backing into a slip at 12 knots is stupid.you could used trolling valves but you should not shift them into foward and reverse while engage they were not built for that.the bertram is very coftable at 3o knots and vicroy said it best ----pussies.
vic i would be scared knowing my props are facing foward --ips destine to fail in a 31 ' boat.

CaptPatrick · Post by **CaptPatrick** » Jan 14th, '09, 18:53

Bob,

This is exactly my point... Much over 320 hp in a B31 is going to require alot of work arounds, maybe prop pockets, weird wheel configurations, fiddlin' with the shaft angle, & etc. Then there's the issue of hull speed. Over 30 kt and the boat is tender, over 32 kt and it's getting squirley, over 34 kt and you're livin' life on the edge, above 36 kt and and you really have a death wish.

For all the money people spend on these boats, why jepordize everything, including life and limb, just to go fast? The B31 hull ain't ment to be a go fast boat...

I know that many have the need for speed, and that's fine by me. I like to twist the wick sometimes too, but only on the right platform.

Br,

Patrick

In Memory of Vicroy · Post by **In Memory of Vicroy** » Jan 14th, '09, 19:27

Capt. Bob the obvious is the forward facing props, but the real killer are the underwater gears and bearings protected by lip seals. Now gonna last, period. I predict Vulva will stick with it, but watch out for the waranty claims.....no way they can honor them 10 seconds longer than they have to.....I been there, done that with their dreaded duo props.....ok if you store out of the water, but in 24/7 a joke.

UV

Harv · Post by **Harv** » Jan 14th, '09, 21:31

The Merc version has the props pointing to the stern.

Tony Meola · Post by **Tony Meola** » Jan 14th, '09, 22:24

The cummins dealer that is hooking up my engines is also a Volvo dealer. This summer he just had to replace a IPS drive out of Point Pleasant that was destroyed by electrolysis.

He told me he can't wait to see one that shears off and someone has to drag the thing home on the safety coil they attach to them. That should be a fun trip.

IRGuy · Post by **IRGuy** » Jan 15th, '09, 00:06

Since I own a B33 I can't comment to add anything Doug33 said above, but didn't I read somewhere on here maybe a year or so ago that if you overpower a 31 hull they tend to lift the stern and dig in the bow?

CaptPatrick · Post by **CaptPatrick** » Jan 15th, '09, 05:37

Frank,

You heard it here... the two power issues that will put a B31s's nose down are severe over propping and over powering. Over powering will result in over propping just brcause the larger wheels are needed to load the engine correctly. The 15Âº shaft angle is too steep for much over 320 hp.

The "Grim Reaper" was a good example of a B31 with too much power & a stock shaft angle. At about 28-29 kt it'd take a nose dive and never see 30 kt... Bruce sea trialed the Reaper in August of '04 and declaired it a dog...

Br,

Patrick

Rawleigh · Post by **Rawleigh** » Jan 15th, '09, 09:56

Bob is a very experienced offshore racer who is willing to live with the compromises of high idle and has the skill set to do it. For me the high idle would be a deal killer, since I troll for Stripers on the Chesapeake Bay and need the slow idle to catch them. Docking would also be a pain at the higher idle speeds.

bob lico · Post by **bob lico** » Jan 15th, '09, 10:34

rawleigh is you have a docking situation like your own canal whereby you just come in on one engine and then hit neutral and just use the rudder to come against the dock softly no problem but if you are in a marina in a tight slip as most of us are you end up in a 12' slip because 14' wide is a premium (pricewise)so you scare the hell out of those on the dock backing up at high speed then 4' before hitting the bulkhead you thown it in foward and the boat stops dead.race boats on the other hand are a real bitch to get around the dock area.you start in neutral warm up shut down shift foward then start in gear get to middle of channel shut down ,shift to reverse start in gear straighten out ,shut down shift foward start in gear allways moving foward to stay in one place once your outside you have to keep circleling ---pain in the ass but this is what you get paid for.getting back to my boat i also fish for stripers however i am not good at it not for lack of fish it is just me.most big cows are taken with liveline.match the hatch sometimes bunker and sometime shad either way you drift so boat idle speed is not important.90% of the time i fish offshore so cruise speed is most important usually 40 to 100 miles off shore.at 30 knot you can go to sleep at the wheel she just cuts thru the water with about the first 3 ' of boat out of the water perfectly level all done by weight distributon and negative rake in props.but you must have the POWER and shaft angle.

Bruce · Post by **Bruce** » Jan 15th, '09, 16:43

Bob is a very experienced offshore racer who is willing to live with the compromises

Is that double speak for Bob's nuts?

bob lico · Post by **bob lico** » Jan 15th, '09, 17:18

bruce i think thats legal talk for a person that has loss his marbles, but then again it is better to love and loss then never have love at all---think about it!!

Bermuda Brother · Post by **Bermuda Brother** » Jan 18th, '09, 18:19

Hey Guys'
Thanks for your responses. I know I will always be destined to catch flak for having the 370's but i bought them more that 2 years ago when the jury was still somewhat undecided at that time. So basically its too late to turn back on that one.

So, if any of you guys have had either the 330's or 370's installed in your 31 with 1.5:1 transmissions I would be anxious to hear what props work best.

Also, the engines will have to be put in the boat very last thing as the boat is on an island on a slip while having the work done so engines would have to be barged over. It will be more practical to tow the 'finished" boat to the engines on the mainland once most of the work is done so its a bit complicated. I'll have to order the shafts from the mainland well ahead of time. For this reason I need to know the shaft length before the engines are in. I am told that it is better to er on the long side as it is easier to have them shortened if needed.

So guys, I hope one of you can offer some specific input on these questions.

I'll have many more questions during the course of the rebuild so stay tuned.
JJ

JP Dalik · Post by **JP Dalik** » Jan 18th, '09, 19:14

JJ,

We've got the 330's with zf 1.5's and 1.5" shafts.

2 sets of wheels both Michigan:

4 blade are 20x25 with a #4 cup high cruise at 2600 rpm 29.2 kts

3 blade are 20x26 with a #5 cup high cruise at 2600 rmp 27.8 kts

The 4 blade offers better cruise spd by 1.5 kts, these are our offshore wheels. Roughly 5 kts at idle with both in gear. Trolling valves for fall striped bass season

The 3 blades offer a slower idle @ 3.4 with one in gear these are the wheels that go on in the spring for our striper season. We usually do a short haul in late July to freshen zincs and change the wheels for the offshore season.

If you've got the 370's I'd think about going to 1.75" shafts. If you decide to stay at 1.5 I'd try to stay at a 20" diameter wheel to reduce stress on the shafts.
Regarding shaft lenght, it all kinda comes down to a final measurement after engine installation, Go a little long if you've got a machine shop to cut them and fit the couplers. Make sure your couplers are faced to be perfectly flat. Just because they might be new does not mean they are right. Good Luck,

Hey look its snowing again

Bermuda Brother · Post by **Bermuda Brother** » Jan 19th, '09, 08:52

Hey JP thanks!
This is very helpful! Out of curiosity what kind of top end you getting out of your rig with the 3 blade vs 4 blades?

Also, am I correct in assuming that the same props run on a 330 should be run on the 370? I am made to understand that despite the difference in horsepower one does not need to increase the pitch for the 370's as these engines only increase the WOT rpm. Is this true? ie what works for the 33o should be good for the 370's?

Also I have a pair of brand new nibral props still in their boxes from my 250 cummins which ran her very well. By the above logic, with the same gear boxes, would these props be appropriate for the 370? Hate to throw them away!

Thanks again!

JJ

JP Dalik · Post by **JP Dalik** » Jan 19th, '09, 10:08

Both sets of wheels top us out around 32 kts. I believe this is more in part to the boat starting to plane over (read as I've reached maximum hull efficiency for standard shaft angles)

The high cruise numbers and top end are good stuff but the real joy comes at 2300 and 25+ kts, this is the real sweet stop for fuel economy on our boat. We can only do this with the 4 blade wheels

If you have 20" diameter wheels from the 250 cummins I can't see any reason you shouldn't be able to repitch them and be good to go. You can run more pitch with the higher horsepower engines because the torque numbers come up significantly allowing you to take a bigger bite on every rotation.

Regarding like for like 330 or 370 I have no idea go online and look for some power curves at Cummins.com you'll see all the info there. But I can tell you that on our boat with a small half tower we are right on the edge of over powered for the hull so keep this in mind when picking a starting point for your wheels. When our engine install was done we purposely tried to keep the engines as far back as we could knowing these boats go over center.

Sounds like for right now wheels are the least of your worries as you've got a whole boat to put together.

scot · Post by **scot** » Jan 19th, '09, 10:33

Here's my 2 cents.

The 370 is too much hp for the 31, but the engine is the correct size, weight, etc.....and the 6BTA's are know to be an excellent power plant.

So, if you found a good deal on some 370's....under-prop them to cruise at 27-28 kts, WOT at 30-32kts. The boat will be strong as hell on the bottom end, the engines will last forever and you will not get yourself in trouble on the top end.

Go with JP's prop set up that he uses on the 330hp 6BTA's.

It's over-propping that kills diesel engines, under-propping is a good thing. Just because the power is there, does not mean you have to apply it to the top end.

bob lico · Post by **bob lico** » Jan 19th, '09, 15:39

one more time cpl numbers or what years are the engines cannot answer question without.

Bermuda Brother · Post by **Bermuda Brother** » Jan 19th, '09, 20:30

hey Bob,
Just saw your message will have to check that info.

Thanks,
jj

Bermuda Brother · Post by **Bermuda Brother** » Jan 19th, '09, 21:01

Ok Pat I do see the light! Basically I have overpowered it which will result in faster idle and nose diving. Unfortunately I got what I got now. So how can I minimize nose diving?
Someone told me that cupping the wheels exacerbates this but isn't this the same as just having a higher pitch? Or is it that cupping in general will increase nose diving more than increased pitch?

From what I have read here am I correct to assume that one in my situation could minimize nose diving by:

Smaller diameter wheels

Lower pitched props

No cupping

Changing transmissions to 1:1.25's to enable using lower pitched higher reving props?

Using 3 blade vs 4 blade props.

So Pat what wheels would you run on my set up to make best out of my situation?
I particularly am interested to know if having no cupping but higher pitch would be better than having cupping with lower pitch or whether this would make a difference to the nose diving tendency at all? Also is it better to have smaller diameter wheels with a greater pitch or large wheels but with less pitch?

How's that for a mind bender boys???
JJ

bob lico · Post by **bob lico** » Jan 19th, '09, 21:01

if thet are recons i will tell you how to identify the "storm block"

Bermuda Brother · Post by **Bermuda Brother** » Jan 19th, '09, 21:02

hey Bob,

They are recons. Not sure what a storm block is though.

JJ

bob lico · Post by **bob lico** » Jan 19th, '09, 21:08

my boat does not nose dive in any way shape,way in every single water conditions,wind,currentwaves,tidal current forget that nosense at 38 knt she flys along the water however to have a idle speed you will have to calm the engine down to 5.2 knt two engines and 4.8knts one engine.the whole job has to be planned carfully and yes you will reinvent the wheel i recomment you put a canvas over the boat and pretent your deaf!!!

bob lico · Post by **bob lico** » Jan 19th, '09, 21:22

there is a plastic foldervwith a seal at the top clip to the engine with about 15 sheets stable to it.open package and go to engine accept report.give me the fuel pump code and the dyno test torque 6th item down. desregard all post this engine and other are like comparing a dog to a cat---other then valve covers and harmonic balencer no other cummins 6bta parts even resemble what you have. block is totally differant made as qsb but mechanical version

JP Dalik · Post by **JP Dalik** » Jan 20th, '09, 07:34

The only marginally successful B31 I have heard of is Pheonix. Its marginally successful because from what I hear it goes fast. However to obtain those speeds it is uncontrollable by the owner during idle and docking situations.
So that boat has been detuned to 32kts!!!!!!!!!

Everyones telling you the same thing. There's only one that I hear works, it took re-inventing the wheel to get it to work and it worked so good that they had to slow it down.

Build your boat for 32kts and it will be safe that is what most everyone is telling you.

CaptPatrick · Post by **CaptPatrick** » Jan 20th, '09, 08:01

So Pat what wheels would you run on my set up to make best out of my situation?

Proping 370 Cummins on a stock B31 is out of my experience range...

Adding cup to the prop has similar result as adding diameter, not pitch. The reason for adding cup is to reduce slippage and increase the efficiency of the prop's bite on the water.

As JP and Scot said, you're going to have to under-prop the engines. If I had to guess, and it is only a guess, maybe 20x22 4 blade w/ a light cup. At least this would give you a set of wheels that could be reduced in diameter, re-pitched, & cup added as neceessary to get you to a max speed of 32 kt.

dougl33 · Post by **dougl33** » Jan 20th, '09, 12:33

That's the first time I've ever heard anyone say that adding cup is like adding diameter. Everything I've ever heard or read states that adding cup is like adding pitch. Its pitch that gives a prop its bite and actually moves it through the water.

CaptPatrick · Post by **CaptPatrick** » Jan 20th, '09, 13:22

Doug,

Pitch alone determine the theoretical linear travel per revolution. Cup grips the water at the end of blade keeping it from sliding off as quick, (slip). But, this gripping action by the cup increases the effectiveness of the prop the same as adding diameter without a cup would.

A 20x24 wheel, theoretically moves 24" per revolution. With no cup, the actual linear travel is less due to slippage. With cup, the wheel moves closer to obtaining the theoretical travel, but still will not exceed the 24". If you had a set of wheels pitched to zero, even a maximum cup would not propel a boat in either direction.

Br,

Patrick

In Memory Walter K · Post by **In Memory Walter K** » Jan 20th, '09, 15:50

As I have understood it, cup works for you at the higher rpm's, not at the low end. If you want to be able to run slow at idle, you don't add pitch as it would move you along faster as it takes a bigger bite every rpm. Wanting to properly prop my boat but keep the low end slow for trolling and docking, as I got closer to getting to spec wot, I added cup rather than pitch to attain my goal. Walter

bob lico · Post by **bob lico** » Jan 20th, '09, 17:19

jp of all the people i respect both you and the captain are on top.if you were to post a new way for stripers with a wooden reel and kite string i would listen with both ears as well as capt. patrick make a new epoxy blend with oil, water and tooth paste.it is not what you say it is the person who says it.were you the slightes bit inquitive on reinventing the wheel?
phoenix is 1000% sucessful i could back her into a slip drunk .the idle speed is partially cause by the damm single lever controls causing the engines to idle at 800 rpm! you have any idea with this bermuda brother has for power this is the real deal and is used as 420hp every damm dat running 8 hours straight.one of the most popular engines today cummins 420hp only this is in deguise.my method of installation is only known by drag boat builders and is a totally differant installation process, but would need harry barb or sim as your best friend!!!
capt patrick you almost had something there every thing you said was correct but next line should be you could take that cup all the way around the blade with minumum slip and MOST of all does not work in when boat goes to reverse.what if you walk into a prop builder and gave him a 23" dyna jet and told him " cut to 21" dia and verible pitch from 24" to 27" skew it and put in 4 degrees of nagative rake" probally the seen from the motion picture " my cousin vinny" when the bama judge says "are you on drugs mister"don`t forget it takes hp to drive that wild cup and big hub that is what the 370 cummins (351hp) is all about.i will deal with bermuda brother as a pm.

JP Dalik · Post by **JP Dalik** » Jan 20th, '09, 19:28

Bob,

Let me clarify. What you did to your boat is fantastic. You had a plan and made it work. You have years of experience making things go fast, what you did to Phoenix makes it a special boat.

For the average fishing guy getting ready to throw big power in a B31 "AND KEEP THE SAME STRUT LAYOUT" its a big bite of the apple (read as "I'm sorry we lost him- he choked on the apple).

Prudence tells me to make safe recomendations. Unless JJ is one hell of a machinist to make new struts and is willing to trim down the outside stringers and find 12 feet of titanium to get the engine lowered in the bay and supported on the outboard side and also able to manufacture one off engine mounts for a 1/2" of hull clearance and do everything else involved with restoring and updating an old B31 I would fall back to- "Go with what you know finish it be happy and go fishing"

JJ- If you've got deep pockets and time I'd love to hear how things are coming along. I'd love to see a diesel B31 over 40kts and safe. However if you don't change your shaft angles (and yes listen to Bob he's got one) you will own the new Grim Reaper.

However I would say use a set of controls with enough throw to get idle and wide open. We used modified Kobelt's (they work OK) but plent of throw- right against the governor every time and back to the idle stops on pull back.

Best of luck I'll be waiting for Capt. Pats water oil and toothpaste epoxy while I'm building a wooden reel, grabbing some kite string and going Striper fishing.

Happy Inaugurination Day.

bob lico · Post by **bob lico** » Jan 21st, '09, 00:05

ok jp now that we are on the same page and bertram brothers we can go on.you have made some very sharp observations.yes the outside stinger is down to a 1/2 " at the rear of the engine.8 million engine installations across the world lets walk away from the boat and come up with a new battle plan base on a 180mph ----hydroplane inboard drag boat like ihrc blown/fuel class.drop the hammer on 2000 hp and 1/4mile later off the "loud pedal".all these boats have one thing in common they ESTABLISH the SHAFT ANGLE BEFORE INSTALLATION.remember the output flange of the gears and the shaft coupling clearance.thown that feeler gauge in the garbage---can`t use it.we are going to make a 1 piece drive train no engine or gear mounts mounts at this time.1st we need harry barb or someone with a shop like his.we mount the shaft coupler on a piece of short 11/2" shaft put in the head stock and make the smallest cut that will clean.coupling face must be square to shaft (90 degrees) and flat.make sure output flange has no burrs or iregularities.next at the boat remove rear bulkhead,shaftlog.the engine is going to damn near sit on the bottom of the boat don`t get nervous we will get back to that.ok lets get out of the boat and have a beer we have to establish a theory that i may or may not describe to well.lets take a prop and put it under the boat just about where it will be and put a 11/2" x 12" pipe thru it.hold the pipe in front and in rear of prop.holding the prop 13/4" from the bottom of boat gently push the pipe up and down(as you would change the shaft angle)you notice something right away as i change the prop angle actually moving on a center line the prop to bottom clearance does not change but the prop moves more parrallel to the water as oppose to parrallel to the boat bottom------------this is speed.a fixed angle for when the boat is riding on the bottom strakes will cause the boat to travel in a level plane IF YOU BALANCE THE BOAT now remove trim tabs you will never need them again unless you f--k up the balance.----getting late i will continiue tommorow.

bob lico · Post by **bob lico** » Jan 21st, '09, 23:59

next step we need harry again we have to mke a template block matching the deadrise and the shaft angle.you don`t have to experiment i am giving you the minumim angle .12 1/2 degrees shaft angle is safe you could go to 12 but present quite a bit more labor.we all know 31 bertram has a constant deadrise of 24 degrees however this is not true in the bilge as you get close to the keel.when they built the boat they kept overlaying at center of keel in side boat so the INTERNAL degrees might end up 20 degrees or less.first level boat on stands check rear gunnel, bridge extension, engine covers,level across entrance to v-berth,front deck just in back of hatch.no twist most be dead level on land.will settle in water but that topic later.now we take verneer put one side on bilge 6" in front of empty hole in bottom created by removing shaft log.put a level on othe leg of veneer make vertical dead level and strike a marker line on bilge floor for referance point.do the same on other side to match.ok now we go to your machine shop.bring two pieces of hard wood like ipe,or oak 2" thick 6" wide and 12" high.you will have to first cut the deadrise you created with the verneer cut that angle with chop saw on both pieces mark one star and the other port.at the machine shop you will set bridge port milller or precision drill press to 121/2 degrees.pat attention to dead rise both pcs will be opposite!!!!!drill 11/2" hole thru.this is your permanent template and will stay in the boat during installation.the next step requires you to cut a 21/2" notch by 6" connected to the old shaft log hole going foward .the new shaft is going to cut thru the bilge floor at a lesser angle .now you have to tell me the diameter of the existing shaft for us to go on.

bob lico · Post by **bob lico** » Jan 25th, '09, 20:34

i guess we will not go on.

JK · Post by JK » Jan 25th, '09, 22:52

Bob,

You make me want to reinstall my diesels and scrap the Solo II controls! Maybe next boat...

--JK

bob lico · Post by **bob lico** » Jan 25th, '09, 23:18

for you jk i would tell the whole story.bruce is telling me i don`t explain myself well here why.i am taking my time explaining the whole installation and i don`t even get a reponse!well the next steps would invove a flashlight type laser and a 11/2" freeze out plug install into the struct.you are finish wilth your bertram and selling it so no use going on with this method of installation you could" have you cake and eat it".bermuda brother apparently listen to his installer who learn fron the guy before him ,you see the pattern here.right know i am involve with the windshield and interior i will get back to redesigning the bridge to accept two raymarine 120 and the controls will be "fly by wire" in time my man and you will be the first to hear about it.

Carl · Post by **Carl** » Jan 26th, '09, 08:41

Bob; I believe you are after a different animal then the rest of us desire. Maybe I should rephase that...I for one would absolutely love to cruise safely at 40 in my 31 Bertram.

Reality...It's too much of a job for the payback. That is even if I could afford the work, motors and parts. That is not to mention I would not trust anyone to do half the amount of work you mention and even if they could do the work, I would never know if it was correct as what you are looking for is based on years of experience and someone like me does not have a clue...that is untill its too late. I think a large % of us got into this boat with full knowledge that as the 31 is laid out the boat is capable of mid 30's...wanna go faster find another platform. Can faster speeds be accomplished...well Dick Bertram proved that with his Nassua race years ago with the 1st 31'sa and you have now proved it can even be done with our Stock looking 31's with lots and lots of work.

I worked on the "fastest sportfish for her size" some years ago. A 92' Lidia with a pair of big Arse diesels with a pair of turbine kickers. The boys that owned her just threw money at her till she was able to cruise 55mph. They could have esily accomplished that earlier but they demanded a stock looking boat and that set up tons of issues. None the less they accomplished it and proved it could be done...but why.

Too much buck for the bang IMHO.

Just my .02...

Carl

Joef · Post by **Joef** » Jan 26th, '09, 10:23

Bob:

I love hearing your whole story on the shaft agle mods. I have a 31 NorthCoast (Darkfin hull). I once spent an hour on the phone with Charles Jannace talking about "shaft angle"...he said most of the boats he designed were never built the way he designed them. ...Blackfin made the boats much heavier than designed, cahnged the balance, moved engines forward or aft because "it was easier to install" etc. He said some of his designs had the engines sitting close enough to the hull bottom, that you'd have a hard time "sliding a piece of paper under them"...exaggeration maybe, but i think the point it, for the effort, you can have MAJOR imprvoments in performance. You used the increase in efficeincy for SPEED...i suppose it could also be used for "economy"...a boat that cruises 25kts with smaller lighter, more fuel efficeint machines. I've fished on a 42 liberty express powered with "small" 420hp volvos...boat felt light and fast and repsonsive and cruised at 25kts, topping out over 30 easily...the balance was perfect and while i don't know the shaft angle, i can tell you i could not fit one finger under the drain-plug on the outboard side of the transmissions.

Anyway - you confirm what jannace told me...its a ton of work to change the shaft angle and rebalnce the boat and it involves changes to the entire drive chain - but the improvements would be substantial

bob lico · Post by **bob lico** » Jan 26th, '09, 10:42

joef that is exactly my point "the engine is one finger off the floor"
A) you lower the center gravity
B) you change shaft angle from 15 to 121/2 degrees
C) the engines are moved 3" further back shifting the weight to stern because even at 121/2 degrees the 350 hp want to put the bow under to fully utilize this power you must plan ahead "it doesn`t just happen"if you are using less power like 300hp then you will have one sweet riding boat and less drag no need to use tabs because your boat is not balance so economy is improved.does it make any sense at all to use a ultra light engine and than ballast the shit out of it to get a good ride???
D) because the engine is sitting lower you can go up and over on the exhaust thus elliminating a dangerous water surge to the engines when backing down.
E) because you are up and over you can use 65 degree fittings on exhaust to reduce H.G to O and use full 6" exhaust
F) create a large empty area under the port and starboard side for huge kill boxes or storage of anchor and 1200' of line.

Joef · Post by **Joef** » Jan 26th, '09, 14:16

PointC) That was the other comment Jannace made...if you need your boat to go fast, then god has ordained that the engines must go in the back. He described a call he got from blackfin when one of their first 31 (or maybe 33 - i don't recall) Combi's "would not perform". When he got there he noted the engines were more than 12" forward of where he had designed them to go.

This stuff gets into somehwat serious engineering. I read an article about boats with these kinds of problems recently - the naval engineer who wrote it described the bow "digging in" as being caused by being "sucked downward" by the flow of water around the forward part of the hull...he referenced taking a tablespoon and holding the back of it against the stream of water from your kitchen sink...when the water is on half speed, the spoon just hangs there...but when the water speed is increased to full power, the spoon literally gets sucked into the stream ( itried this when my wife was not looking and can tell you guys its true)

Anyway bob - when you moved the engiens backward, did you then need to reposition the aft bulkhead ( and the associated deck supports and engine boxes? I'd imagine you get great speed and lower RPM - to put into efficiency perspective do you know what your best "NMPG" is?

Bruce · Post by **Bruce** » Jan 26th, '09, 14:47

If I didn't know better I'd swear we were reinventing the wheel here.

You can make anything work up to a point whether that point is to tell everyone I told you so or to have a one of a kind is up to the owner.

Money and time can produce much.

This boat runs fine in a certain speed/hp corridor without much modification to the boat itself which makes modernization of the 31 a reasonably priced deal.

Going outside of the corridors presents bigger challanges and design characteristis that other makers of boats had designed into them in the begining.

Why put a big block in a garden tractor when John Deere makes a tractor that will do the job already?

The 370's will work without much modifactions by using a 1:1 or 1.25:1 gear box.

The lost factor is the hp of the engines. You'll never get the full potential out of the 370hp with that gear ratio in the 31.

But if that's not a problem and someone already has the engines and wants to do as little as needed to run that boat its quite simple actualy without having to break out the slide rule.

bob lico · Post by **bob lico** » Jan 26th, '09, 17:43

honest bruce i not reinventing the wheel just reducing the shaft angle from 15 to 12 1/2 degrees.in reallity all the person has to due is notch that shaft log foward .i have already done the ground workfor angles.what the hell he has to go to a 11/2" shaft anyway why not use capt patrick`s shaft log idea just put the new shaft log into the notch.bruce what are we talking about slightly more woven roven and epoxy!the 370 hp cummins is about 351hp you know that so lets not get crazy your idea of 1.25 on top of the reduced shaft angle with utilize all that 350hp and back off to 2500 rpm. of course you would install a " normal" set of thottle controls so he can cruise at 30kns----no big deal.just a little more money for a huge gain.

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