Bertram 26 Propeller Size/ Speed Issue

Captain Cuda · Post by **Captain Cuda** » Mar 15th, '11, 00:12

Hello,

I am a big fan of the forum. I am hoping one day to join the faithful and rebuild a 31 Bertram.

I am trying to finish up my current project first.

I have a 1983 26 Bertram. I have not found a sandbox for the B26, so that is why I am posting here. I recently repowered with direct replacement 229 cu in 165HP Pleasure Craft Marine engines,new everything except transmissions.

The wheels are supposed to be 14X14 michigan dyna jets according to my book. I get full RPM, 4000 +. At 3200 RPM I am doing around 15 knots.

Does that sound right? I have read the small amount of literature that is available on this boat and I thought Id be closer to 20 mph, knots, something like that. Right now, Im cruising about the same speed as my old 25 Luhrs with a 318 Chrysler. I hated that boat. And I am ripping my hair out over this.

Love the boat, if she was faster. Really like the fuel burn. Wish I had put in twin v8s.

Carl · Post by **Carl** » Mar 15th, '11, 13:07

Welcome Capt Cuda!!

Lots of great people with lots of excellent info here.

I'm not familiar with your choice of power,,,but I would have thought 4000RPM was low for max WOT.

If your supposed to spin faster, I'd address that first...you don't want to be burning valves right out of the box.

Increasing speed can be done by increasing pitch and/or Cup size...but each will bring down your WOT RPM. 1" pitch or a cup size equates to aprox 200RPM ...not something you want to do if your at or low on WOT RPMs.

Prop style and brands can be played with as well....but I'd run it past a good prop shop first. JB Propellor is the best in your area.

Carl

In Memory Walter K · Post by **In Memory Walter K** » Mar 15th, '11, 14:57

My first question would be, what WOT is that engine rated for? I agree that 4000 rpm SOUNDS low. My Merc 3.0 on my B-20 is rated at 4600-4800. With the proper prop, you should be able to hit the rated WOT.

scenarioL113 · Post by **scenarioL113** » Mar 15th, '11, 15:55

Are these v6's or inline 6's?

Are these Inboards or Stern Drives?

Rated RPM most certainly would be more like 4800RPM

You should turn rated RPM at WOT with no problem to be propped correctly. I think your over-propped which is not good.

A friend of mine had a B26, looked like a mini B28 except it had stern drives. That boat was pretty fast with the Inline 6 mercruisers he had and it burned no fuel too, prob the most economical gasser I ever saw.

He cruised over 25 knots if I recall correctly.

In Memory Walter K · Post by **In Memory Walter K** » Mar 15th, '11, 16:23

Capt. Cuda- Since you are a single engine, when properly propped, you will probably be in the 19-20 range. Don't feel bad, that's what our local waters let me run my diesel B-31 at without jarring my teeth. At Marine gasoline aiming at $5.00 a gallon, you will be far more economical than if you had twins. It seems affordable fishing may become a thing of the past.

tunawish · Post by **tunawish** » Mar 15th, '11, 17:10

Walter, I think he has twins unless i read it wrong...???

Ray

In Memory Walter K · Post by **In Memory Walter K** » Mar 15th, '11, 17:22

Ray, after rereading his post, I think you may be right. That being the case, he should be definitely getting 20-25 at cruise.

Brewster Minton · Post by **Brewster Minton** » Mar 15th, '11, 18:17

I use to have 165 perkins in my 31 and it went 19 knots. That boat should go way faster then 15.

BCBertie · Post by **BCBertie** » Mar 15th, '11, 19:23

I have a 1976 26 FBC that was originally equipped with inline Chevy sixes coupled to Gen 1 Mercruiser outdrives. It now has 3.7L 4 cylinders in it, and cruises at 25 with a top of 30 kts.

If you need any help, just let me know.

Cheers!

John

Harry Babb · Post by **Harry Babb** » Mar 15th, '11, 20:01

Brew wrote:I use to have 165 perkins in my 31 and it went 19 knots.

Hey Brew.....just a slight difference in TORQUE.

An old friend had a 30 foot Sportcraft.....Single 454 with 1-1/2:1 gear and only cruised at 16/18 knots and burned a lot of fuel.....way to much fuel! ! !

He sold the boat before he would let me experiment with props....I always thought that boat should cruise at near 22 knots....but he was satisfied just as it was.....

I have an old Chaparell 244. I ran a 15 x 14 (as I remember) and it cruised at about 23/25 MPH at about 3200 RPM. One day I found a prop that came off of a 175 BlackMax.....14x17....so I just had to try it. Well it did not work.
My engine still turned 4400 WOT but the boat simply did not move as fast. As I remember 3200 RPM Cruised me at 15/17 MPH.

First of all I am not a prop guy....so I am disqualified to give advise....but Cuda, if I were in your shoes the first thing I would do is go to as much dia as I could get....15" or 15-1/2" I think is the max you can put on a Merc Outdrive.....and drop my pitch to around 12" or 13"......then when that did not work I would get me a beer and say to my self "Well Crap! ! !"

hb

bob lico · Post by **bob lico** » Mar 15th, '11, 20:18

those dyna jets are inboard only so i assume you are running b/w gears . lets start by tell us what gear ratio the gears are then we will go to the props as said above something is wrong but we need the gear ratio first.

Harry Babb · Post by **Harry Babb** » Mar 15th, '11, 20:43

Ops! ! ! for some crazy reason I thought we were talking Merc Outdrives.....

My guess is more dia and less pitch......

hb

Captain Cuda · Post by **Captain Cuda** » Mar 16th, '11, 07:06

1983 26 Bertram with Inboard Crusader 3.8L 165HP V6s. The gears are Borg Warner 1.5:1 reduction gears. The Bertram book that came with the boat from the original owner I purchased the boat from specs a 14X14 wheel, which the boat spun no problem since 1983.

The engines that came out had 1700 hours on them and were not running were full of sludge from ethanol in the OEM fuel tank. I went back with an aluminum fuel tank. I replaced the old engines with what are supposed to be PCM 3.8L 165HP V6 direct replacement counter rotating engines new off the shelf from a guy in South Florida who got them from the PCM warehouse in South Carolina.

I have had lots of issues with my "new motors" and the company I purchased them from is no longer in business and Pleasurecraft didn't want to talk to me when I had a knock in the "new" engine and an oil leak in the two piece rear main seal. We have rebuilt an engine, had countless ignition and timing problems, carburetor issues, you name it, it has gone wrong.

WOT is supposed to be 4200 RPM with these engines. I hit 4100 on my old Tachs if I let them spin up.

These are strange engines. They were only manufactured for a short run, when compared with the 4.3L V6 or all of the 305/350 V8s. Crusader and OMC marinized the engine during this brief run of I believe 4 years. Basically, if my B26 was built in 1985, they would have installed 4.3L V6s at 190HP each (had I done more research, I would have corrected this before I purchased the engines)

My fear is that these engines were a poor marinization by Pleasure Craft Marine, and they have the wrong Camshafts and are actually 140 HP engines. That would explain the slower speeds a crossed the board and low WOT speed.

Carl · Post by **Carl** » Mar 16th, '11, 08:25

If 4200 is what your supposed to turn and your getting 4100...your right in the ballpark...although I'd verify the Old tachs just to be sure...but chances two tachs being off the same amount is slim.

If your turning up to rated WOT...your choices become slim as you cannot go up in Pitch or Cup as you do not have the hp to push more wheel....

Props have been checked out by a Good Prop Guy??

-A prop that is out can rob power without giving you the push.
-Different Wheel designs give different performance. A good prop guy may be able to offer alternate styles, brands pitch, cup and rake combination to give you better performance in your application.

In my last boat I went from a 15mph cruise to 20 by going with a Ski-Boat design prop...same RPM, Same WOT, Same fuel burn...just faster and a good deal more money.

Playing with Props can get very expensive if you cannot borrow and change out props yourself...I am lucky as I was able to borrow a dozen and jump in water and change them myself.

Other things you can check...make sure everything is running free. Shaft is aligned, can be turned easily by hand... Rudders are aligned properly...not toed in or out too far. How is boat load...weight can slow you down. Or if trim is wrong when running.

You mentioned motors where killed by ethanol....By any chance did you bring the carbs over from those engines?...may have clogged passages, jets, choke not opening fully.

It is real difficult to know if your running right without a baseline to go by...in your research have you found the stated speed with your setup. You may just be running correctly.

Captain Cuda · Post by **Captain Cuda** » Mar 16th, '11, 09:39

My research which really only consists of what guys say their boats do trying to impress me is that they all do around 20 knots. More likely they are saying 20 MPH in which case- it can do 20 MPH but you gotta run her like 3500. When I did that the ignition problems started happening.

Trim is not an issue- the boat was not built with trim tabs. She may be running correctly- low and slow. I am not a picky guy when it comes to speed. I have owned several boats. 20ft Shamrock- 18-20 knot cruise. 26 Pacemaker with a diesel- 20-22 knot cruise. 26 Shamrock with a diesel- 18 knot cruise. 25 Luhrs 15 knot cruise.

I operate a 110 foot 300 passenger tour boat with a 14-18 knot cruise depending on the price of fuel.

I am not an outboard guy bent on speed- I am trying to make sure that this Factory stock Inboard 26 Bertram is running correctly.

The props seem like they may be under the 14X14 size which is stamped on the hubs. The prop scan showed them as being about 13.8 in diameter- but I do not 100 percent trust where I took them- they have a tendency to grind down everything and never put anything back.

My father tends to think a new set of 14X14 would be a good place to start. He is usually right.

bob lico · Post by **bob lico** » Mar 16th, '11, 13:05

sim say it all i cannot say it better------good luck brother

Captain Cuda · Post by **Captain Cuda** » Mar 16th, '11, 19:37

Prop guys specs a 15X14- we will see

Harry Babb · Post by **Harry Babb** » Mar 16th, '11, 22:30

Keep us posted.....from my limited experience I think the larger diameter will do you good.

A local mechanic repowered a 31 several years ago. He put Big Blocks in and a 2.5:1 or may be a 3:1 gear and proped her with over square wheels 20?x24? as I remember.

The owner bragged about how smooth it was and how much less fuel she burned.

If I had deeper pockets (wallet) I would have done something like that with DeNada......but decided to be safe and go with the tried and true as I had been advised here.

Keep us posted

hb

Chanse · Post by **Chanse** » Mar 17th, '11, 00:14

Im not sure if this could be any help or not.
Idid a little search and found a 83 B26 twin inboard
with 205HP 4.3 Vortec V6's running 14 x 16 nibrel props cupped.
This was in a ad.

Captain Cuda · Post by **Captain Cuda** » Mar 17th, '11, 08:23

Does anyone here know a good place to check the price on new 15X14 bronze wheels? or used since this is an experiment...

Carl · Post by **Carl** » Mar 17th, '11, 10:01

15 x 14 s Blade Bronze wheels, 1" shaft list for $621.00 each...but for an experiment I'd be looking to borrow a set of used wheels...or buying used wheels.

I have a pair of used 15 x 11's for 1-1/4" shaft in Nibral...again not great for an experiment as cost to re-pitch Nibral is $$

If your going up an inch in diameter you will be losing RPM at WOT unless you come down in Pitch or Cup...your already on the low end of WOT. Prop guy knew your WOT info?

Tony Meola · Post by **Tony Meola** » Mar 17th, '11, 20:22

http://www.atlantispropeller.com/propellers.html

Call th Atlantis Propeller. They have a repower deal. Give them the power, model yr of the boat, weight if you know it, etc, and they can come close to what you need almost first time out of the box. They give you a free adjustment on repowers when the props are purchased from them.

They also sell used props.

Carl · Post by **Carl** » Mar 18th, '11, 06:03

Tony Meola wrote:http://www.atlantispropeller.com/propellers.html

Call th Atlantis Propeller. They have a repower deal. Give them the power, model yr of the boat, weight if you know it, etc, and they can come close to what you need almost first time out of the box. They give you a free adjustment on repowers when the props are purchased from them.

They also sell used props.

Bingo

Captain Cuda · Post by **Captain Cuda** » Mar 18th, '11, 07:01

Already had General Propeller in Florida run this boat through there computer. 14X14 or 15X14 for less slippage. $450 each. Great Guys. But if I can find used to fit, I'm buying used to try it.

You say I am on the low end of WOT. Does anyone here have experience with 3.8L V6 Marine Engines? Does anyone here know where to find info about 3.8L V6 Marine Engines? I have been looking/ searching and due to the short run it is like trying to find a needle in a hay stack. I cant even find another boat on the planet that has 3.8L V6 Marine Inboard Engines, other than the 26 Bertrams built in 1983 or 1984.

I measured the props I got- I get a 13" diameter. My local prop guy cut em down and left the 14" stamp

Now if I buy 14X14 thats fine but I may get the same performance. If I buy 15X14s and they are over loaded, I can always cut down the 15 inch wheel- I cannot make the 14 inch wheel bigger.

Carl · Post by **Carl** » Mar 18th, '11, 16:01

Captain Cuda wrote: WOT is supposed to be 4200 RPM with these engines. I hit 4100 on my old Tachs if I let them spin up.

That would explain the slower speeds a crossed the board and low WOT speed.

I measured the props I got- I get a 13" diameter. My local prop guy cut em down and left the 14" stamp

Now if I buy 14X14 thats fine but I may get the same performance. If I buy 15X14s and they are over loaded, I can always cut down the 15 inch wheel- I cannot make the 14 inch wheel bigger.

Maybe not my place...but you really need to figure out some basic information.

If your supposed to run up to 4200 at WOT and your only at 4100...not great, but your in the ballpark. But now you say your only turning 13" wheels and considering going to 15" and keeping the same pitch. Sounds like a short way to kill your motors.

If it where me...I'd verify the Rated WOT for those motors.
Make sure your running gear is all as it should be and verify the prop specs you have now.

Something just sounds wrong...

In Memory Walter K · Post by **In Memory Walter K** » Mar 18th, '11, 22:39

Go to the larger size (diameter) with the same pitch and I'm pretty sure you'll lose rpm. I agree, get verification of those engine's rated wot. If it IS 4200 (that's an area of doubt in my mind), I'd drop the pitch an inch or two. I suspect the larger diameter will give you more push for the same rpm's.

Captain Cuda · Post by **Captain Cuda** » Mar 19th, '11, 12:23

WOT from a guy with the exact same boat- 4200 RPM- 1983 26 Bertram with 3.8L v6 Crusader inboards with out the dinette option and with a raised hardtop and full enclosure.

Swings a 14X 14 Nibral prop with a cup

at 3200 RPM runs along at 20.5 knots.

My actual prop diameter is 13.5" measured on a flat surface. My props are bronze. My cup is non-existent.

In Memory Walter K · Post by **In Memory Walter K** » Mar 19th, '11, 12:51

The cup helps only on the top end of the rpm spectrum. Helps a lot on my diesels because cruise is only 2-300 rpm under wot. 3200 rpm out of 4200 wot, a prop guy will have to tell you. I have a set of Nibrals and a set of Bronzes and to be very honest, see no appreciable difference in performance in the 20 kt range I usually run in. I see a fairly big difference in costs should I need to have anything done Nibral vs Bronze.

BCBertie · Post by **BCBertie** » Mar 19th, '11, 12:53

I think the key to your trouble lies here:

"I have had lots of issues with my "new motors" and the company I purchased them from is no longer in business and Pleasurecraft didn't want to talk to me when I had a knock in the "new" engine and an oil leak in the two piece rear main seal. We have rebuilt an engine, had countless ignition and timing problems, carburetor issues, you name it, it has gone wrong. "

The book props should get you to 4200, *if* the engines are in good shape and tuned properly. If you can't get there with a smaller prop, then it is likely your engines are not delivering the same hp/torque curves as the originals. As everyone has said, increasing diameter will only lose rpm...

Good luck.

John

Carl · Post by **Carl** » Mar 20th, '11, 09:04

Captain Cuda wrote:WOT from a guy with the exact same boat- 4200 RPM- 1983 26 Bertram with 3.8L v6 Crusader inboards with out the dinette option and with a raised hardtop and full enclosure.

Swings a 14X 14 Nibral prop with a cup

at 3200 RPM runs along at 20.5 knots.

My actual prop diameter is 13.5" measured on a flat surface. My props are bronze. My cup is non-existent.

Okay, hate to be a bastard...but where did he get his numbers? If from the motors User Manuals your golden..if from local mechanic or its just what he has always run..then I'd be calling into marine motor dealers and requesting that info. For me...I believe everyone...and then verify.

I'm also not one to believe coincidence...so sounds about right. If it is...you need to find out whats happening to the lost power.

I think you have two avenues to explore:

- You engine is not producing rated HP

- Something is robbing the hp.
Bad alignment
Bad running gear...binding, bent
Rudders not aligned
Bad wheels
Hull not smooth, clean
Overloaded

If you trust the shop that did your wheels, your running gear is in good shape and your boat hull is clean and not overloaded...I'd be looking at motors again...fresh motors should push an Under-size wheel over the rated WOT, the smaller diameter should be slipping, your speed would not be there...but the WOT RPMs should be over the rated WOT RPM. Unless to compensate for being under-size the prop guy added pitch...but you said 14" pitch...so I'm going with that.

Seems like you have been working on this project for some time....how old is the fuel...was it stabilized?? This Corn fuel loses its "umph" as the alcohol evaporates away... I'm kind of reaching here...but unless you know where the boat ran prior to the engine problems, with those props and running gear, your your flying blind. Is it the motor/motors, the prop/props or something else...

If it was me...I'd start by eliminating as many variables as possible. Running gear and Wheels should be easy to check..then it leaves motors.

Can you swap wheels with other guy with same boat???or just ask him to run your wheels and see what happens...I'm thinking he Over Revs them and goes slower.

Bruce · Post by **Bruce** » Mar 20th, '11, 15:00

Reality check 101.

Book props usualy are close especially if you can find someone that has the same setup to compare to.

Now if your running the same engine, gear and prop combination and cannot achieve max rated engine rpm as measured by a hand reflective tach for accuracy then you have engine issues.

No amount of money spent with a prop shop is gonna cure that. If you cut the props down to gain rpm, your just going backwards.

V6 engines in themselves are dogs. OMC used that engine so you might be able to find info thru them although if they are PCM converted I've never known PCM not to help a customer if they can.

One thing they won't do is be a mechanic for you.

Unless they came completely assembled and freshly painted then it sounds like what you may have gotten was possible rebuilts even using auto based short blocks which aren't designed to give the same performance as the marine.

First thing I would do is get the block numbers on both engines and make sure they are pleasurecrafts and not auto based. From there you can determine to move forward or dump the two into a land fill.

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Bertram 26 Propeller Size/ Speed Issue

Bertram 26 Propeller Size/ Speed Issue

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