Mercedes 300 d in my Bertram

Hello all, New to this site. Pretty excited, in the middle ( after ALOT of research) of converting my twin Engine Bertram from Ford 351s to Mercedes Diesels. Found a company in the Netherlands that actually makes a conversion kit to turn a Mercedes 300d 5 cylinder in line diesel turbo into a boat engine! Instead of using a Hurth transmission I am using a Borg Warner,seems to be just fine so far.. Have one Engine in and complete and running.This boat is a shaft drive,so no problems there. So far so good, they do this in Europe commonly, but have rarely seen this done here. Be dropping the second engine and tranny in the next couple of weeks. Just wondering if anyone has seen this and should I expect any unforeseen issues?

 

Tell us more, GC.
What do you mean by shaft drive?
There are a number of issues in conversions, but maybe you’ve already researched them and have answers.
Thrust from the prop is handled?

DC

 

Sounds like a 28 ft Bertram. What is the output of the Mercedes motor ?

 

You are reducing the power from about 280HP to 83HP on each. Basically, the boat will not plane. If you are OK moving at less than 10 MPH (hull speed) then the conversion will be acceptable.

 

Turbocharged version produced 227hp. Cooling, like always, may be the bottleneck.

 

I think you were a little short here on detail Gonzo in an otherwise informative post.

What will happen to fuel economy under the hump?

 

The original 351 Ford is 280HP which made the boat plane. The MB 300 is 83HP which is less than 30% of the design power. At the most, it will get the boat to the point of squatting. I suppose the economy of the small diesels may be good for someone that only needs low speeds. If he expects the boat to plane as before, it will be a disappointment.

 

He specifically stated turbocharged. Turbocharged versions produced up to 227 hp.

Lowest power turbocharged was 123hp.
Marinized 351w range from 220 to a few at 285. Depending on version he may only be losing a bit of power.

Or a lot of power. I can't find anything useful online about marinized OM617's. The conversion kit nay be most bodaceous. Or not.

 

Gary, what's the output of your converted om617"s?

You may need to reprop to get on plane.

 

I missed the turbocharged . However, there will be at least 45% and at the most 67% power loss. Those were not overpowered boats so either way I think it is a problem.

 

Accept the lower top speed, reprop for the new hp/torque curve?

We got your back, Gary.

 

Thanks everyone for the input, toanswer a couple of questions, with only one engine in,I think that Im going to have enough power,very unweildy driving it with one,but even with one engine,I can at least get it on plane.not going to put it backin the water until I get both in. Had to work on the trailer,so I got a chance to see it run a little. Had to get a custom Ujoint made to connect the 1 - 1/14 shaft to the tranny, I think that the props are correct, the prop guy did the math and we are using the same 3 blade brass props that the 351s used , well see. This Bertram does not have trim tabs, doesnt need them, one of the reasons I picked this particular boat for this project, pops up like a cork on plane even just a little above idle. A couple of other things that are cool is the fact that, by replacing these heavy 351s, the weight difference between the two motors is alot, with the risers, my estimate is about 200 lbs difference PER engine weight wise. No salt water will touch these blocks, all big heat exchangers bought from a company called Mr. Cool, transmission also. I do, however need some advice on externally cooling the engine compartment and turbo. Thinking of running a couple of inline blowers into the compartments creating kind of a positive pressure situation? Had to custom make the exhaust, right now am using 2-1/2 in black sprinkler pipe with a up and down rise of about 16 inches ( to prevent any sea water from entering) and the exhaust water brought in at the end of it. Seems to work ok, am going to eventually remake these out of stainless .One of myquestions is where to put zincs? Am wrapping the exhaust with heat wrap about an inch thick, not sure about the turbo, how to wrap or coat it?

 

Blowers need to suck air out of the engine compartment. Overpressure will fill your boat with hot engine smell.
Get a book called Boat Mechanical Systems Handbook, by the sainted Dave Gerr. All your questions answered there.

 

Yea, Im not too worried about a little loss at top end speed, I just want to be able to work this boat and run all day with no issues at medium speed. The engines dont have any electronics to worry about, I have put twin seperator filters for the fuel and already installed a new custom 100 gallon aircraft aluminum saddle tank. Put an overheat alrm and a working oil pressure gauge. Have I missed something? Am also doing something a little different with the boats power supply, am installing a solar system as primary power for allof the needs on the boat, will talk about that later. Thanks guys.

 

The engineroom will need ventilation because of the turbos. You could put insulation blankets on them, but as far as I know they are not designed for it and the bearings may overheat. The air intake would benefit from being routed out of the engineroom. Exhaust fans and properly sized inlets will help keep the temperature down. Are you changing the original oil cooler to a heat exchanger?