Engine repower gas to diesel

[popeyefoghorn]

I have a 1978 Chris Craft Catalina Express, 29ft, single 305 Marine Power. I was just wondering... if I was to repower and put a used diesel engine in...would it work and how would I decide on engine size, hp, etc. thanks, eh!

 

[QC]

Re: Engine repower gas to diesel

How much horsepower do you have now? Are you happy? The answer to those questions will lead you to the hp answer.

I would try to stay near the same weight first. You don't want to mess up the way the boat sits and handles. Newer 5 and 6 liter diesels will easily make that kind of power but will probably be heavier, so you need to think that part through.

Next issue will be the reduction gear ( I am assuming inboard). When you lower RPM and get the same bhp, you also just increased input torque. Your trans needs to stand that because the only way that you can take advantage of the lower RPM rating is to use a lower numerical gear and/or bigger wheel. You must achieve some sort of reasonable output shaft speed is another way to put it.

 

[popeyefoghorn]

Re: Engine repower gas to diesel

The engine I have in it right now puts out 225 hp. These boats also came with twins (not sure what size engines though). I'll look at the spec's on my tranmission. And get back to ya.

 

[popeyefoghorn]

Re: Engine repower gas to diesel

Is a 6 cyl. diesel about as big as the foot print of the 8cyl. gas engine? Just curious what would fit into the space.

 

[QC]

Re: Engine repower gas to diesel

Most in-line 6s will be longer and taller although a little narrower than your existing V8. Go here for some good info:

Cummins 4.2

There are some good drawings etc. here that detail the dimensions. I can't find the weight without an outdrive even though they have specs for an inboard . . . Whatever. Maybe you've got better eyes. It appears that even this little 4.2 liter could outperform your existing engine depending on the rating. These high-performance, smaller, modern diesels are going to be hard to find used . . .

Ian, I assume that you plan on keeping this boat and simply want a diesel. If you are doing this to save money, I can help prove that you never will get a payback. It just depends on your motivation. I have been selling diesels my entire career, I guarantee, unless you are a commercial fisherman this will not pencil out from an economic standpoint. If the coolness factor, safety, etc. etc. are enough to motivate you then great!!

 

[Don S]

Re: Engine repower gas to diesel

Depending on the engine you go with, you will also need to replace the transmission. Mostly because of gear ratio's and bellhousings to adapt to the engine.
Then you get into prop size. Due to the extra torque of a diesel, you may have problems with getting a prop of the proper diameter in the gap between the hull and centerline of the shaft.

Here's a link to older Volvo diesels you could use for size and weights also, you would be looking for something in the 41 series such as a TAMD41.

http://www.volvo.com/volvopenta/glo...es/older_engines_1/2002/dieselengine/inboard/

 

[MADONN]

Re: Engine repower gas to diesel

The easyest fit is a 6.5 gm diesel bolts right up to your bellhousing. But be prepared to spend some coin you will need a flywheel, starter, manifolds, risors, and heat exchanger with all the plumbing. I am doing one as we speek I make my own bio diesel and its going to be worth it for me to run the diesel.

 

[Ldavidgrover]

Re: Engine repower gas to diesel

The Styier Diesel 256. Everything bolts up the same and is a fuel injected high rpm motor. The 256 will perform if not better than a 454 gas

 

[aerobat]

Re: Engine repower gas to diesel

Newer 5 and 6 liter diesels will easily make that kind of power but will probably be heavier, so you need to think that part through.

hm... newer diesels will make this and more power being an inline4 with 3.7litres displacement. - such volvo penta D4-260 here from year 2004 e.g .

http://www.bootsmotoren.de/Volvo-Penta-D4-260-I-A.html

it will be similar weight ( or lighter) than your 225hp V8 and will outperform it easily.

in times of high boost turbocharging and direct injection no need for 6cylinder 6litre to push 225horses.

its a question if the price is an option.

 

[QC]

Re: Engine repower gas to diesel

Uh . . . this is almost a 6 year old thread guys. He was talking used at the time, but I guarantee I understand power density, and was even suggesting a 4 liter

Let's let this one sink to the bottom.