Car to boat engine replacement?

[drrm123]

I have a 1981 Beachcraft with 3.8 OMC which may have a cracked block or blow headgasket. I was wondering if I can replace the engine with an automobile engine either a chevy or buick 3.8 around the same year?? Would rebuild and use orginal intake and boat cam?

 

[Chris1956]

Re: Car to boat engine replacement?

You can do it. You should replace the freeze plugs with brass ones and be sure to use the original boat ignition system, starter, carb, alternator, thermostat, exhaust manifolds and water pump. You will also be forced to reuse the boat's manifold cover and (likely) the intake manifold.

Wouldn't it be easier to replace the head gasket, if that is the problem?

 

[whywhyzed]

Re: Car to boat engine replacement?

1978-1984 Monte carlo, some malibus, elcaminos even some 1980 Camaros. But be careful, some of those corporate GM models got the Buick engines - you want the Chevy 229 not the Buick 231- both were called "3.8" by GM.

You also have a PM in case you are local to me I have a lead on a replacement.

 

[drrm123]

Re: Car to boat engine replacement?

Thanks for the info how important do you think the cam is? Using an auto cam as opposed to a boat cam. Will try to find the lift and duration of both to compare. I'm not sure if its the head gasket yet? This is a used boat that I bought about 2 weeks ago. i could tell water was in the oil and it's kind of hard to turn over but will crank? I don't know how much rust is built up inside the engine that's why I wanted to know if I could get a car engine as a donor. Will pull exhaust manifolds and heads this week if it doesn't rain.

 

[whywhyzed]

Re: Car to boat engine replacement?

if the block isn't cracked I'll eat my shorts....
I put a youtube video up of pressure testing a 3.8 block - very easy - go watch it.

3.8 + automotive cam = 120HP
3.8 + marine Cam = 170HP 2BBL / 185HP 4BBL

The cam is where ALL the power comes from in these motors - the car cam was smogdog city

Edelbrock 2112 practically identical grind to the OMC marine cam - summit has em for $130ish

 

[drrm123]

Re: Car to boat engine replacement?

I have water in all three cylinders on the right and water in the oil. I changed the plugs today and it fired right up ran 4 about 20 seconds checked forward and reverse which were good. Is it normal for these blocks to crack boats in california and does not usually get cold enough to freeze if water was still in the engine.

 

[Silvertip]

Re: Car to boat engine replacement?

Buick built 3.8 has the distributor in front. Chevy 229 is 3/4 of a Chevy small block V8 so the distributor is at the rear. Nothing on these two engines interchange. Even the bell housing patterns are different.

 

[Haut Medoc]

Re: Car to boat engine replacement?

I have water in all three cylinders on the right and water in the oil. I changed the plugs today and it fired right up ran 4 about 20 seconds checked forward and reverse which were good. Is it normal for these blocks to crack boats in california and does not usually get cold enough to freeze if water was still in the engine.

I'd look at the riser/man or the gasket between on the side with water....
The water in the oil may be caused by that, but if you change the oil & it happens rapidly, it is a cracked block or head.....

Pressure test the cooling system....

 

[drrm123]

Re: Car to boat engine replacement?

I have some snap on pressure testing equipment for an automobile radiator which attaches in the place of radiator cap. But on a boat is it possible, I thought water would flow in and out of engine constantly(not a sealed system). This may seem dumb but this is my first boat or any experience with one. Also what's the riser/man.

 

[whywhyzed]

Re: Car to boat engine replacement?

did you watch the video? It shows you what to do about that

 

[drrm123]

Re: Car to boat engine replacement?

I've been working on boat past couple of weeks and have fixed most minor problems got trim motor to work and tilt system to work fixed oil pressure sending unit. Still need to determine if its a blown head which I believe it is. will take boat out this sunday and see how fast water gets in oil. Bought all safety equipment I needed and a rope to be pulled back in if necessary. Will post findings when done.Thanks for all info again.