Pre-'86 to post-'86 Chevy 350 engine swap

[Uraijit]

Well, as some of you know, I bought a boat with a bad engine. It's a 1981 Sea Ray 195, with a Mercruiser 260 (Chevy 350) and an MC-1 outdrive.

I got the engine pulled last weekend, and now I'm ready to go get a new engine. I decided to convert it to CNG (compressed natural gas) because CNG is $0.68/gallon, while gasoline is $3.86, and rising.

Anyway, I've located a 1988 Chevy C1500 pickup with a CNG system already in it. I'm going to check it out, and see if the CNG system is compatible with the marine carb for a dual fuel setup (for those long lake trips where I can't get to a CNG station). I'll be able to switch back and forth between fuel types.

Anyway, being that the engine in the boat is pre-'86, and the truck is post-'86, I know that there's some sort of adapter required. What is it called, and how much do they cost?

Also, what else should I look for? I hear that there are issues with starters not matching up, and flywheel sizes.

Anything else?

 

[tmh]

Re: Pre-'86 to post-'86 Chevy 350 engine swap

BOOM!!!!!!!!!!!!!!!!

Scared ya. I hope.

 

[Uraijit]

Re: Pre-'86 to post-'86 Chevy 350 engine swap

 

[TilliamWe]

Re: Pre-'86 to post-'86 Chevy 350 engine swap

Well, the flywheels and the starter are different. I'll assume the truck motor is going to have just a flexplate, not a flywheel. You'll need the equivalent flywheel. Get the starter with the "new" motor and then match it to a marine starter. Your coupler from the old engine probably won't fit the new flywheel, but I am not positive about that.
Not sure what adapter you are talking about, the outside dimensions and bolt patterns should all be the same.

 

[Uraijit]

Re: Pre-'86 to post-'86 Chevy 350 engine swap

Well, the flywheels and the starter are different. I'll assume the truck motor is going to have just a flexplate, not a flywheel. You'll need the equivalent flywheel. Get the starter with the "new" motor and then match it to a marine starter. Your coupler from the old engine probably won't fit the new flywheel, but I am not positive about that.
Not sure what adapter you are talking about, the outside dimensions and bolt patterns should all be the same.

I'm guessing it's something to do with the coupler. I've just read that you have to purchase a new part to make it meet up with the drive. If I recall, it was a triangular shape...

 

[tommays]

Re: Pre-'86 to post-'86 Chevy 350 engine swap

I can say without a drought the CNG system is NOT marine rated

It is best to NOT mix the years for and EASY job

The bolt pattern on the flywheels is different

The newer auto block may not have the stuff for the mechanical fuel pump(cam lobe or even the mounting hole)

 

[Uraijit]

Re: Pre-'86 to post-'86 Chevy 350 engine swap

I can say without a drought the CNG system is NOT marine rated

It is best to NOT mix the years for and EASY job

The bolt pattern on the flywheels is different

The newer auto block may not have the stuff for the mechanical fuel pump(cam lobe or even the mounting hole)

You'd be right that the CNG kit is not "marine rated", however, there are zero electronic parts anywhere near the engine, and the beauty of CNG is that it's LIGHTER than air. So if there are any problems, the gas will not collect in the bilge, because, unlike gasoline, it will rise, and vent out.

If I have favorable results, I am looking into getting a CNG kit "marine rated" with the Coast Guard, and will start selling kits/performing conversions.

I probably won't end up using the newer engine anyway, but I'm still curious about the "adapter" (coupler?). I'm pretty sure it was someone on this forum who told me about it, but nobody seems to know what I'm talking about now.

 

[TilliamWe]

Re: Pre-'86 to post-'86 Chevy 350 engine swap

I now know what you are talking about and it's the engine coupler, not called an adapter. Yes, you'll need one that fits the different flywheel used on the 1987 and up motors. Readily available Mercruiser part, just more money, that's all.

 

[Uraijit]

Re: Pre-'86 to post-'86 Chevy 350 engine swap

Thanks, that answers my question.

I got on ebay, and found some for around $150. Not worth it, when I can just buy a salvage yard engine for $50, and put that extra hundred bucks into freshening it up with new rings and bearings.

Thanks again for the help guys. I shoulda known it was too good to be true.

I'll probably still buy the truck if the CNG kit is in good shape. I have a buddy who needs an engine for his '94 Suburban, and I can always just sell the body for scrap to recoup some cost...

 

[subcrx]

Re: Pre-'86 to post-'86 Chevy 350 engine swap

coupler wont bolt up, I almost learned the hard way on that

 

[Coors]

Re: Pre-'86 to post-'86 Chevy 350 engine swap

I dunno if I would freshen up a boat engine; it's not as easy as swapping engines in cars. Get a reman.
It will be worth it in the long run, not to have to do it twice.

 

[subcrx]

Re: Pre-'86 to post-'86 Chevy 350 engine swap

true, I looked at mine when it had trouble. Worked itself to death. I got my new motor out of a c1500 and had it converted over for marine use. Not back in the water yet but it is running beautiful, all im waiting on now is to get my outdrive back

 

[Uraijit]

Re: Pre-'86 to post-'86 Chevy 350 engine swap

I dunno if I would freshen up a boat engine; it's not as easy as swapping engines in cars. Get a reman.
It will be worth it in the long run, not to have to do it twice.

Not sure what you mean by this, but the engines are virtually identical. Pulling the engines from boats is actually EASIER than pulling one from a car.

If you're talking about the block itself, I'm going to marinize it with brass plugs, and non-metallic head gaskets. Depending on what engine I pull, I'll probably just leave the cam alone if it's a truck cam. If it's car cam, I might drop the bucks for a marine cam, but I'm going to try and avoid having to do that.

I'm quite familiar with rebuilding engines. Lapping some valves, re-ringing some pistons, and honing cylinders is not rocket science. Hell, I may just replace some bearings if they need it.

Not sure how you figure paying $1500-$2000 for a "marine" long block is worth more than spending a weekend pulling an engine for $50-$100, dropping another $100-$200 into parts to rebuild it, and being on your merry way.

Even if I had to spend 20 hours on that, I'd have to make $85/hr, to justify the time savings. I don't even make CLOSE to that --not even half that-- so it's hardly worth the money to me...

I'm not going to put a $2000 engine into a $1200 boat.