Need for speed

JimmyG · Post by **JimmyG** » Sep 23rd, '13, 23:38

I'm closing in on my restoration job and starting to think about power, being a hot rod at heart i always had a need for speed! I know I know " how many days can you go over 30 knots" I hear it all the time but I would rather be looking at it then for it. I turned 54 this week and well this is my last restoration job so any recommendations? I had 6 LP's in my last Bert and I was able to cruise at 32 Knots I was told someone has the new V8 375 HP Yanmars in a 31 that is pushing 40 (could be salesman BS) I guess the only other alternative is Cummings....any thoughts?

Rocky · Post by **Rocky** » Sep 23rd, '13, 23:59

Here ya go. Except I cringe every time I see tunnels being put in this one!
http://www.sbmar.com/repowers/shooter_t ... m_odyssey/" onclick="window.open(this.href);return false;

SteveM · Post by **SteveM** » Sep 24th, '13, 03:40

A guy approached me in the yard last summer to discuss his B31 project and his method for achieving more speed.
He is putting the engines in reversed and utilizing jack shafts. Along with this he will have no thru hull fittings other than one for a single/central box that all will draw off of. No bottom paint, as he will have it on a lift and bottom will be smooth finished.
He got the idea for the jack shafts from the S. FL Yanmar distributor who has a few of these boats. They estimated speeds over 40 knots while still only using 315hp 6LP's.
The explanation for reversing the engines was to get a better shaft angle that produced more thrust.
He lost me on the engineering of this, but it was an interesting enough story that I remembered it.

Bruce · Post by **Bruce** » Sep 24th, '13, 07:18

What a complete and utter waste of money and power on that 440 job. Another prime example of more money than brains and zero engineering understanding and what it takes to match engines with boats and utilized that package to its potential.

Like the boneheads at the track who put big block power in and got their ass beat by small block performance. There's so much more to just dropping in a large engine.

At least 35k more than a pair of 315 and only 8 more knots?
One would be better off putting in a pair of gas engines if speed is all one wants.

On shaft angle, there is just so shallow an angle you have to have to fit the prop under neath without tunnels or using stern drives or arneson surface drives. On a 31 it isn't going to be that critical cause many gas 31's are going over 40 knots as is.

Pete Fallon · Post by **Pete Fallon** » Sep 24th, '13, 11:22

JimmyG,
If you want to go fast put in a set of Mercruiser 7.4L BlueWater Throttle Bodied Fuel Injected Engines. I didn't want diesel smell in my 1961 Express Cruiser cockpit, I did a lot of low speed trolling for Giant Tuna up North and Sailfish down here in Florida. The station wagon effect at low speeds can produce a smelly cockpit in an express cruiser. I researched and talked to a lot of knowledgeable engine mechanics before buying the engines.
For the best fuel economy, speed and ease of maintenance I chose the Mercruiser 310 hp with 8 degree down angle Hurth trannies with 1:5:1 gears FWC. I get 41.8 mph at wide open throttle at 4400 rpms, cruise @ 3000 rpms @ 30 mph and slow troll at 1500 rpms @ 2.5 mph. Fuel burn is variable depending on loading & sea conditions, but I have never been able to burn more than 22 gallons per side at 4400 rpms which is wide open throttle. The injection system is 2 injectors per engine where the carb would be, both engines are fresh water cooled from the factory. These engines have electronic control modules for timing, air and fuel mixing . They run smooth and have built-in knock sensors, never smoke and never had any ethanol in them or the tank.
The above system used my existing 1-1/4" Monel shafts and a 17"x18 pitch 3 blade bronze Nybral props. They also have 5" FRP exhaust tubing with under the deck Vernay mufflers and 6'' stainless outlets at the transom. They also have stainless steel exhaust manifolds and in a 31 they need the 3" extension risers above the manifolds to keep the exhaust water from backing into the engines.
So if you want to go fast without out running the vessels bottom,I would recommend the Mercruiser 7.4 L FWC TBFI with Hurth 8 degree down angle trannies. The only draw back is they are no longer made by Mercruiser , but if you can find a set that's the way to go. Forget the 440hp diesels, a waste of money, time and boat modifications, the best diesel would be the Cummins 270 remans.
Pete Fallon

Rocky · Post by **Rocky** » Sep 24th, '13, 11:45

Yep thats what I thought too on big heavy diesels compared to high speed gas if you want speed. Close second I guess would be the Steyr high speed diesel line, but pound for pound top end gas wins. Holy crp did our 427 side oilers run our Bertram fast at the top end- BUT close to 60 gph wide open..How fast do you want to go would be the question.., and at what cost.

JimmyG · Post by **JimmyG** » Sep 24th, '13, 14:47

I guess "i want my cake and eat it too" first and foremost I'm a offshore (60-120 miles Hudson to the Norfolk) fishermen so the reliability and economics of a diesel is a must, I am not real crazy about prop pockets either, i will have a bottom smooth as silk also thinking about shaft tubes (haven't totally researched them yet) Bruce I'm with you I had a small block chevy in a 1972 Vega that would blow the doors off the big blocks! I know Wharton creek were putting in the 375HP Cummings in there restores but I dont think they were getting as much out of them as the 6 LP's i was just wondering if there was any other alternative

Craig Mac · Post by **Craig Mac** » Sep 24th, '13, 15:15

Regarding shaft tubes---the seem to be more trouble than they are worth. I know of a couple of boats that were retrofitted with them, that eventually went back to standard shafts. I really don't know what the problem was, I am speculating it was alignment issues.

Bruce · Post by **Bruce** » Sep 24th, '13, 15:34

There really isn't much in the 315 to 350hp range which is the Ideal diesel power range. The other issue you have to deal with is what do you need in the way of trolling speeds and will it take going with trolling valves to achieve that due to higher hp slower turning diesels and the props they have to spin to load them up.

Yanmar's 8lv is all electronic. Keep that in mind. Don't have any feed back on them at all at this point.

Since the 6lp's went away, I would be looking at the Cummins reman program for engines in the 330hp range.

Tony Meola · Post by **Tony Meola** » Sep 24th, '13, 21:35

Jimmy

The only other option is go the Bob Lilco route and basically you almost put the oil pan right on the hull to change the shaft angle. Re-do the struts for the angle. But Bob has issues ideling slow. Issues if you want to troll real slow.

I have the 270 Cummins reman. I am running light so tough to go by me for what she will do. At 2200 and my Bimini up, I am running close to 23 knots. At 2400 I am at almost 25 knots.

My Bimini gave up the ghost this year and I have not replaced it. My speed changed drastically. At 2000 I am at 22 knots at 2200 I am just shy of 24.5 knots. The Bimini's are like a huge parachute from what I can see.

SteveM · Post by **SteveM** » Sep 25th, '13, 10:12

I agree with Tony, I notice a difference with the Bimini up. It IS like a parachute.
Even while docking in windy conditions I take it down, otherwise the wind pushes the boat around like it has a sail.

JP Dalik · Post by **JP Dalik** » Sep 25th, '13, 19:40

QSB 305's have more torque then the 330's we are running. There is a B31 up here that was done with those engines and its remarkably quiet, smoke free and quick. With 4 blades we are only 32.5 kts in the corner, the 305 boat I think is closer to 35 kts, If you do go electronic pay attention to the extra space the computer boxes are gonna require, there will also be some additional filtering that should go in place as the common rail engines like very clean.

Capt.Frank · Post by **Capt.Frank** » Sep 25th, '13, 20:47

I thought the 300-330 hp boats could cruise at 27-28 knts a and 32 WOT? I have 3208NA 210 hp and cruise 22knt and 27 knts WOT clean bottom and marlin tower and curtains. So the 270 hp cummings are 25 knts cruise 28 WOT. So does this sound right ?

Tony Meola · Post by **Tony Meola** » Sep 25th, '13, 21:21

Frank

If it doesn't blow this weekend I will take her out and put her to the pins without the Bimini and give you the top end. With the Bimini up, at the top end I hit 30 knots. Remember I am light, no tower or hard top. Traditional Bimini. If I remember right JJ (John Jackson) with the 270's was doing 24 to 25 knots at 2400 RPM's with a hard top, and Radar.

I was told 2200 is the cruise, but not to worry the engines will run at 2400 all day long without flinching. I trust my mechanic, he has not steered me wrong yet.

Rocky · Post by **Rocky** » Sep 26th, '13, 07:02

So, question perhaps for Bruce here, I know Jimmy is got the need for speed, and I think it would be nice to be able to have a good top end "clip" at times if conditions allow- could you/someone tell me what the advantages of the 6BTA mechanical but 370 hp would have over the 330 and visa versa? Would the 370 allow more options as far as engine to boat matching or is the 370's torque and horsepower curves not suited for the 31? It was my understanding what makes the rating higher is you can spin the 370 up higher through the injection pump/fuel increase. Possibly be able to get your idle/troll speed a bit lower from making the 6BTA more of a high speed diesel, does this sound accurate? The QSBs are a lot more money otherwise I would look into them, I do love the idea of extra quite just not at that price especially the techniques you can do to quite the mechanicals through isolation/insulation.

CaptPatrick · Post by **CaptPatrick** » Sep 26th, '13, 08:20

There are two primary factors that limit the upper power options for the B31.

Most importantly, in my opinion, is that the hull design allows the boat to plane at a relatively slow speed, beginning around 13 kt, but is limited, in terms of safety, to around 34 kt. Above that speed the B31 becomes progressively unstable. At 40 kt I consider the B31 to be dangerously unpredictable as it is literally balancing on the four inner most lifting strakes with the chines well clear of the water. It takes very little effort to loose that balance and fall off to one side or the other. A gust of wind, a crossing wake, a bit too much rudder, a change in current direction, or a shift in load can all lead to an abrupt change to the planning attitude. When that happens at above 35 kt, there is the potential for the chine to grab water and almost instantly, and dramatically, change the direction of the boat.

This has happened and is NOT theory....

The other factor, is proper loading of the engine. The more horse power a marine engine develops, the larger the diameter and pitch of the prop has to be to utilize that power effectively and efficiently. With the stock shaft angle of 15º and the standard strut configuration, a 20" diameter wheel is a safe diameter. 21" is the maximum diameter without modifying the hull and struts. Above 320 hp, the necessary prop diameter can't be fitted under the stock hull/strut configuration. A 21" diameter wheel could be fitted without modifications, but the pitch would have to be so great that trolling/idling speeds would be excessive.

Everything has it's limitations. Just because we might lust to exceed those limitations doesn't make them go away....

The need for speed is perhaps OK, but only under the proper conditions, personal abilities, and equipment. You can't shoot the moon riding a bottle rocket.

JimmyG · Post by **JimmyG** » Sep 26th, '13, 11:26

Capt Pat you and the faithful are always a wealth of information , I do remember when I first installed the Yanmars taking it out for a test ride the boat was real light and the steering was hooked up wrong steer left i would go right and and it was down right squirrely AT 35 knots. I would like the same performance I had with the LP's, I didnt need trolling valves (2:1 gears) 20-23 Acme 3 blades so if i cant get the LP's anymore what would be a good substitute ?

SteveM · Post by **SteveM** » Sep 26th, '13, 13:21

Jimmy
There's probably a way to get 6LP's. I'm an optimist.
They can't be sold to a USA customer. I was able to purchase them as my boat is titled in the Bahamas. We did the install work here....and no one checked anything.
Probably more of an issue to the Yanmar distributor than it would be to you. I think they need a breadcrumb trail.
Steve

JP Dalik · Post by **JP Dalik** » Sep 26th, '13, 20:48

The boat I'm talking about has 305 QSB Cummins runs 4 blade 21x24 dqx Michigan wheels tops out at 35.2kts and burned 138 gallons of fuel on its last trip out of Manasquan to the Toms a distance of roughly 84 miles.

The boat burned roughly 30 gallons less than we did with better speeds and less horsepower on the same trip. His fuel burn was consistent with a 6B 270's for that trip. Gentlemen there is no substitute for torque and the QSB Cummins has loads of it. Just remember if your going over a diameter of 20" for wheels upgrade to 1.75" shafts to be on the safe side.

Craig Mac · Post by **Craig Mac** » Sep 27th, '13, 15:55

JP--what is the name of the boat with 305's

bob lico · Post by **bob lico** » Sep 27th, '13, 20:33

Craig the reason they had trouble with the F/G shaft logs was because they were stupid! No further explanation !

bob lico · Post by **bob lico** » Sep 28th, '13, 08:42

Designed by capt. Patrick and built by myself the shaft logs has been flawless for 8 years.along with blue printing strakes adds 1/2 knot or in my case same speed at less rpm ( fuel economy). Went 91 miles round trip to offshore wreck on 50 gallons of fuel. Full boat ( chine 5" under water at transom ) boot stripe completely under water . 30 knot cruise in 4' waves all day. Tony remember I can care less about idle speed! Idle speed only a drawback for 2 mph speed trolling for bass ,for that one use maybe 5 times a year I use trolling valves .

bob lico · Post by **bob lico** » Sep 28th, '13, 08:42

bob lico · Post by **bob lico** » Sep 28th, '13, 08:44

Craig Mac · Post by **Craig Mac** » Sep 28th, '13, 17:00

Bob,

I was not referring to shaft logs----I was referring to shaft tubes----the entire shaft is in a tube .

Craig Mac · Post by **Craig Mac** » Sep 28th, '13, 17:00

Bob,

I was not referring to shaft logs----I was referring to shaft tubes----the entire shaft is in a tube .

Bob H. · Post by **Bob H.** » Sep 28th, '13, 18:56

Craig, I have not heard too many good things about the shaft being enclosed in an oil bath tube..Cooks the oil many switch back to dripless..BH

bob lico · Post by **bob lico** » Sep 28th, '13, 19:21

I a with you bob nothing good about the entire tube enclosed. I experimented and came up with 4" from hull to tip of enclosure with cooling water off gear cooler. Water forms a sheet and goes around totally ferred area reducing hydrostatic to less then 10 percent. Rotating shaft is not the real deterant to hydrodynamics ,the suction of the exit of OEM shaft thru shaft log is the real culprit. Moving a reverse angle over a body of water is a real bummer in the speed world.lesson to learn!!!! Whenever you build or change hull in the interest of more top end speed you must consider EVERY factor the water entering a Bertram prop pocket is totally agitated negating any advantage of decrease prop angle . Yes idiot you also cut out the stern edge of the lifting strakes and destroyed all advantages of a multi straked Bertram. Essentially you have added increased surface friction area! Prop pockets are like cursing out my mother lets not mention such a moron move on this board again! Shear stupidity I will run any FBC prop pocket bertram for pinks and spot shooter 250 hp !

scot · Post by **scot** » Sep 28th, '13, 22:17

Capt Frank.
Your 3208NA 210hp engines are basically permanent in a weekend boat. 210hp coming from over 500 inches could see 25,000+ hours. No turbos, no inner coolers = simple and less maintenance issues. For my screwed up back and 2 bad knees, I would enjoy a day on your boat running 22kts with 4,000lbs of engines in the Gulf's short wave period MUCH more than I would in anything doing 35kts that weighs less than 40,000lbs.

"back in the day" when I made my living in the Gulf, I would take a 150-200 ton steel work boat at 12kts over a 85-100 ton aluminum crew boat at 20kts any day of the week.

I'm with Patrick on the low cruise speed being the big attribute of the original Hunt design. Going 13kts in really snotty stuff is a very good trick indeed.

Just me, In a weekend pleasure boat I prefer a decent cruise (anything at, or over 19-20kts) and HEAVY. Makes for the best ride in my neighborhood.

John Swick · Post by **John Swick** » Sep 29th, '13, 17:44

SteveM
You were referring to someone reversing the motors an using jackshafts to reduce the shaft angle ?
Did you mean v drives ?

What about using v drives to reduce shaft angle ?
Too much shaft ?
John

Capt.Frank · Post by **Capt.Frank** » Sep 29th, '13, 21:57

Scott,
I don't mind 22 knots cruise but have a 20 mile run to inlet and it would be nice to run 27-28 knots during that trip. Yes I like the extra weight in the iron as UV would say. I was just surprised to here that the speed with 270 Cummings were not that much more than me. Doc had 4BTA 250 in his and he would cruise 25 knots. Brewsters boat is pretty quick with yanmars. But have no time on another B31 with Cummings power. I washed a cylinder 2 years ago and needed a new block (3208 non sleaveable ) I was looking at 6BTA but could not come up with extra money. I love the simplicity of my cats and no turbo wine.

scot · Post by **scot** » Oct 4th, '13, 21:03

Frank, The non-replaceable sleeves is definitely the short coming of 90% of the smaller diesels (like most in these size boats) It's a real bummer to wash a hole and need a new block. I'm surprised it could not be over bored + liner. The best setup is a wet sleeve IMO, but you don't find that design in these smaller, modern, light weight engines.

I rode in Capt DQs 31 with the 6bta 250hp engines, ran great with a mid 20's cruise. The 250hp is a nice set up in the 6b's as they use a fresh water cooled after-cooler. Cuts WAY down on after-cooler maintenance.

Tony Meola · Post by **Tony Meola** » Oct 4th, '13, 21:57

Frank

I felt the same way you do, but after the Cummins dealer who also handles Yanmar, went over every thing with me, the only option that made sense were the 270's.

AS he kept saying to, Tony it's a 30 foot boat. How often outside of cutting the bay are you going to really run her faster. Then I remember a post JP had one time, he had some thing like 30 Canyon trips and said he figured out he averaged 14 knots due to conditions.

Then I got the, fresh water after cooler speach, so the 270's went in.

JimmyG · Post by **JimmyG** » Oct 7th, '13, 23:04

OK reality came and smacked me in the face, I found a new pair of LP's holly S#!T!!!! $61000.00!!! I know prices have gone up but I had no idea, I paid $36,000 in 2000 I might go with remans anyone know a good source for Yanmars LP's or Cummins 6BTA 5.9

Tony Meola · Post by **Tony Meola** » Oct 7th, '13, 23:08

Jimmy

I think you are in NJ. Try John Lane up at Forked River Diesel and Generator. He is both a cummins and Yanmar dealer. Tell him Tony Meola referred you.

ed c. · Post by **ed c.** » Oct 8th, '13, 13:09

Jim, if you buy my boat you will have a pair of 315's. 1592 hours.The highest cruise I ever had was 34.4 kts.

bertram31.com

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