Repowering Questions/Advice

[Vince Luciani]

Hello everyone,

After owning a 31’ Bertram for 8 years with old Detroit Diesel 4-53’s (many looonnggg canyon trips), I’m finally ready to take the plunge and repower. Those engines owe me nothing! They served their duty well and never let me down. If truth be told, I might have even been inclined to live with them if they weren’t so damn dirty. I’m fearful the Coast Guard is going to get me for oil discharge. My crew has nicknamed the boat the “Valdez”.

Anyway, I’ve decided on the factory remanufactured Cummins of the 300 hp variety. I’ve also decided to tackle the project myself. I’m a civil/structural engineer so I think I can handle the layout. Also, I have 2 cousins that will be helping me who are diesel mechanics, so I think we have a qualified crew.

I’ve been researching this project for years and have been collecting info from this site, as well as others, to try to prepare for the day that I decided to tackle this project. However, I still have a lot of questions. For starters, here are some:

•I have 1 3/8” diameter shafts and I intend to install 1 ½” diameter shafts. Will I have to replace shaft logs or can the existing logs be used? They appear to be in good shape. Will I need to replace the struts or can they be bored to accept the larger diameter shafts.
•What size props are recommended for 300 hp?
•Will I have to change the current shaft angle so that I can get the clearance required at the prop end? My boat is in the water and I can’t measure my current prop (18”x18”) clearance. But, I’m wondering if Bertram used the same shaft angle regardless of the power installed. It seems like the job would be a hell of a lot easier if you don’t have to get into replacing struts, changing shaft angle, etc.
•If I install ZF220 transmissions (with 10 degree shaft angle) can the engines/transmissions be mounted pretty much square to the stringers and give me the clearance at the props? Or will they need to be inclined for even greater than 10 degrees?
•Has anyone mounted engines using 1 foot sections of 1/2” thick, 6”x6” aluminum angle through-bolted to the stringers? I’ve seen this setup on other boats and it looks fairly easy to set up. However, is it strong enough? or do I have to go with the setup like Patrick used on those Yanmars of “Buddy Boy”?
•Do I go with 5 inch diameter exhaust or 6 inch diameter exhaust?
•What size of water intake is recommended? External strainers are preferred, right?

That’s it for now. I won’t actually do the installation until next spring, but I will get started on the preparation (i.e., removal of old engines, cleanup, paint, layout, engine mounts, water intakes, etc.) as soon as the boat comes out of the water at the end of November.

Thanks to all.
Vince Luciani

[JP Dalik]

1. The shaft logs are usually best replaced with the glassed in tubes. Neater and safer when done right. Depending on which vintage strut you have it may be able to be bored out or you may be able to use thin walled cutlass bearings.
2 With 300hp I'd try to start with a 20"Dx23"P 4 blade propeller and adjust from there.
3.The stringers will need to be strengthened to support the extra torque of the engines, you would be best served to do what Capt. Pat did on Buddy Boy.
4. 6" Exhaust is best 5" is right on the edge.
5. I think its 2" intakes, maybe 2-1/2 but that sounds big Look at Cummins.com and check the specs. Our boat has on got the eel grass strainers under the hull and works great

Read the specs on Cummins.com the 330hp engine is better on fuel and makes more torque then the 270's At speed you can run more rpm and burn the same amount of fuel (this is on paper now) as the 270's right through to 2600 rpm. The 330hp versions will be lower in the engine box due to the way some plumbing is run.

You will have more maintenance with the 330's as the heat exchanger and cooler will need to be cleaned.

[Bruce]

Vincent,

Shaft logs will have to be changed. My advice is also get the aftermarket struts cause the lower rpm motors can swing a bigger prop and boring them out is marginal at best.

You will need 6" exhaust with cummins.

Props will depend on the gear ratio you use.

You can't use 6" angle on the current 1" wide fiberglass stringers.
First they will sit to low, second they need to be beefed up in width for strength.

I would use the external strainer pickups.

There are two different stock shaft angles, measure which one you have before you decide what gear ratio to run cause you may have to change it.

[scot]

Vince...
1) what is the cruise speed on your 31 with the 4-53's? 2) Stand by to fly with 330 Cummins...basically 2X the power. Better ad a general review of everything bolting onto the boat. When you start bouncing around at 30kts you'll find all the loose stuff.

I suggest you go to the Boatdiesel.com site and use their prop / shaft / horsepower calculators to get some ideas on various requirements, performance and/or running gear sizes. Read their discussion boards in the Cummins B Series section and you will get some major info on those engines. Good luck, it sounds as if you are doing your home work.

[Vince Luciani]

Thanks for the information. It is very helpful in my planning. I guess the message is, if in doubt, err on the heavy duty side.

Scot, I currently cruise at about 17 knots, so a mid 20 to 30 knot cruise range is exciting to say the least. I understand your comment about bolting everything down. I rattled loose alot of equipment on my old boat, including my body.

I would really prefer the Cummins 250 hp models, but they tell me that these are not available in the cummins factory remanufactured engines. If anybody has any leads on decent 250 hp cummins, I'm all ears!

Thanks again guys,

Vince

[scot]

Keep an eye on the "Gold Coast Power" board. Those guys have a lot of used and reman engines. I've never heard of any complaints about John, althought any company that has been around as long as they have has one or two unhappy customers out there somewhere.

[jav]

Vince,

a pair of 250hp cummins were listed on boatdiesel today or yesterday. They are in Rhode island... no affiliation but I did by my used diesels from them.

[John Jackson]

Vince,
I'm getting 270B's put in mine right now. I've been watching pretty closely and it seems like a very complicated job to me. Seems like the type of thing that would be really hard to do for the first time. For example, the yard where I am has done dozens and they have mock ups on the engines that they used to set the shaft log angles and the angle of the engine.

Today I stopped by the yard and they had just removed the front cowling covers off of the engines and rerouted the hoses because they know that it won't fit the way it comes out of the box, and while you would get the engine in, you would never be able to remove the cowling.

They also said to forget about internal sea strainers because they take up too much room, cost thousands and don't do much more than the externals. They cited a couple of new boat builders who don't put them in and said that they have had no problems.

They also relocated the raw water pickups and installed all fuel lines and filters before the engines because they knew where to put them and how hard it is to put them in once the engines are in the way.


I was advised to get the 270s over the 330 because of the maint, the need for bigger shafts and I was told that its hard to go slow enough to troll for stripers with the bigger engines. Plus I was told that you would only get about two more top end knots. The boats with the 270s all seem to cruise at 26-27 kts. JP could give you more info on the bigger motors.

Your welcome to take a ride up here and look at my installation if you want to. It might be worth the two hour drive. I'm sure JP would be happy to show you his boat too. If you wait a month there will be another 15 or so B-31's in the yard that you might be able to get look at under the engine boxes. Good luck, and if you want me to I could send you emails with pictures of the steps of my install.

[scot]

Vince,

I'm not certain but I think I remember from prior post that Uncle Vic has the 4BTA's 250hp in his B31. You may want to check with him about performance, fuel burn, durability, etc.

Watch out for the injectors, Cummins has experienced a problem or two with those otherwise great little engines. From what I read they have solved the problem with the latest P/N release and some owners suggest that you not cruise above 2400 for extended period if you want the injectors to last boo-Cu hours.

[Rawleigh]

I'm pretty sure Vic has 6BTA's.

[In Memory of Vicroy]

Yeah, I have the 6BTA 250s, CPL 1247 built in Nov. of 1989, guess they are vintage now. Have about 2400 hours. Over that time not one injector has been removed, the valves were adjusted at 1000 hours, and that's about it, other than changing the raw water pumps at 1200 hours or so. Changed both exhaust manifold-to-turbo gaskets within the last couple hundred hours with a new hi tech one as the old gaskets were weeping a little coolant.

Bulletproof engines all the way. The 4BTA 250s are a little different, higher rpm, less cubes, and had bad injector problems out the chute, but the fix was a new injector and Cummins fixed the busted pistons caused by the snapped off injector tips.

My B31 FBC, pretty heavy with a 6.5 kw genset, half tower, big chair, etc will cruise at 24.5 kts at 2400 rpm at 16 gph including the genset. Top is about 27 kts at 2650 rpm, don't know the fuel burn there. Load means nothing with these engines, 13 people and all their gear, still 24.5 kts. Dead idle at 700 rpm is 5.1 kts thru 1.5 gears and 21x22 three blade props. One engine idle is 3.2 kts, can be done well with Capt. Patrick's oversize rudders. Idle them down below 700 and they lope pretty bad and the gears rattle a lot.

The 270s are the same engines as my 250s, just rated a little different. I've had a lot of different engines over the last 5 decades, but the Cummins 6Bs are far and away the best - simple, easy to maintain, and mostly not a lot of bell & whistles to go bad. Just big ole happy chucks of iron.......

UV

[scot]

Sorry UV,

I got it half right...I remembered 250hp. Oh well, my wife blames my poor memory on a mis-spent youth....much of which I cannot remember either.

Scot

[JK]

Vince-

I will be brining the boat up from OCNJ this weekend and will be keeping her at the Lagoon in Essington, PA. You can come and ckeck out the install anytime you want, boat will be about 15 minutes away from either the ben Franklin or WW bridge. The install is holding up well but the guy certainly didn't go out of his way to do an incredible job. He simply cut down the wood stringers, capped with with aluminum, stregthened everything with aluminum crossbars and plopped the engines down on them. So far so good. If I could do it over, I would rip out the wood stringers and build up from the glass stringers with SS or something of that nature. That would give much more access to the underside of the engines and would eliminate the chance of the original wood weakening overtime. 300hp 6BTA's, 1.5:1 ZF 220a trans, 20x23 4 blade nibral props, spin 3000+WOT and still am pretty linear with rpm vs speed. Fuel burn is crazy, out of IR most we ever took was 132 and that was a 15 hr trip to the south Washington canyon, cruised at 2600rpm for the 3+ hrs each way and trolled all day as well. These engines are from the late 80's too, are a little loud, smoke some but are bulletproof so far. Come check out the boat anytime...

john