81 mercruiser 3.0 same as 3.0 chevy?

[alnrs1963]

I just bought a very clean 81 Bonanza with the 3.0 mercruiser 140 hp 4cyl I/O. This boat has 89hrs on it & by the condition of the interior & flooring I am inclined to believe it.
Now for the problem, the motor is out of it & I am told by the owners that the block, manifold & head are all cracked. Don't know how, just that they are. I am considering the lock stitch method to fix the block but not sure yet.
My question is; will an engine out of an older Chevette be the same motor (besides the manifold that is)? I have found a very low miles 76 Chevette & I was told they are the same engines. I can get it for a couple hundred bucks so thats pretty reasonable. I only paid 500 for the whole boat & if I can get the thing in the water for around 1500 total i will feel pretty good about it but I also don't want to do things half way. Sorry if I rambled too much, any ideas & also if the engines are not the same do I have to stay within a certain year range when considering replacement engines?
Thanks, Alan.

 

[Rocky_Road]

Re: 81 mercruiser 3.0 same as 3.0 chevy?

The camshaft will be wrong...maybe yours can be reused?

The freeze plugs in the marine block are brass, and need to be non corrosive.

Let some wrench heads jump in here, and add to (or straighten out) what I have said!

Happy boating!

 

[Bondo]

Re: 81 mercruiser 3.0 same as 3.0 chevy?

My question is; will an engine out of an older Chevette be the same motor (besides the manifold that is)?

Nope,... Not even Close...

& also if the engines are not the same do I have to stay within a certain year range when considering replacement engines?

Ayuh,... There's a rear main seal size/ style change around 1990 or so,...
Most of the other subtle changes are non-issues or easily adaptable...

Other than That,...
It's pretty much the same motor as it was in the early 60s...
A Marine/ Industrial, Non-automotive motor....

 

[alnrs1963]

Re: 81 mercruiser 3.0 same as 3.0 chevy?

Well that's a start, thanks. Now I guess the search is on. Still going to take the block to the local machine shop for an opinion on pinning or lock n stitch. Have read some pretty positive results, pretty handy with a wrench & such but going to leave that one to the experts.

 

[fishrdan]

Re: 81 mercruiser 3.0 same as 3.0 chevy?

A few other things different between 3.0 (140/135/130HP) Mercruiser engines:

- Rochester or Mercarb carburetor
- 3 or 4 different manifolds
- 3 or 4 different heads
- 2 different flywheels
- different starters
- 3 different ignitions
- location of shift cables

And probably other things I didn't list, just make sure what you are buying is going to work.

 

[alnrs1963]

Re: 81 mercruiser 3.0 same as 3.0 chevy?

I have all of the original items such as flywheel, ign, starter, manifolds & even the block. I havent looked at it yet to see the cracks though.

 

[180shabah]

Re: 81 mercruiser 3.0 same as 3.0 chevy?

Repairing is NOT an option. Your machine shop will not be able to get to all of the internal cracks. So your money will be wasted. Same goes for the manifolds.

How did it happen? you ask. Improper winterization, water in the cooling system froze, expanded and cracked the iron.

Shop around, you can probably find decent engine in a rotted out hull for cheap.

 

[fishrdan]

Re: 81 mercruiser 3.0 same as 3.0 chevy?

I have all of the original items such as flywheel, ign, starter, manifolds & even the block.

Yes, but make sure what ever parts you buy are compatible with each other, the engine, drive, etc. IE: an old style larger port manifold isn't going to work worth a sh!t with a new style small port head.

 

[alnrs1963]

Re: 81 mercruiser 3.0 same as 3.0 chevy?

I am going to try & just get an entire engine assembly. Found one out of a '77 boat so I hope that it will just mount up.

 

[cr2k]

Re: 81 mercruiser 3.0 same as 3.0 chevy?

The 3.0 is strictly a marine or industrial engine and was never put in autos.

 

[mattyrich]

Re: 81 mercruiser 3.0 same as 3.0 chevy?

Yes, but make sure what ever parts you buy are compatible with each other, the engine, drive, etc. IE: an old style larger port manifold isn't going to work worth a sh!t with a new style small port head.

I have been searching everywhere for this answer, sorry to but in...

My question is this... What about the other way around. will a newer style manifold fit on an older style head? I know that the older style heads have six bolts and the newer ones have five but it is the same pattern, and i dont see why it wouldn't work, and i cant seem to get a concrete answer from anyone? thanks.

 

[Bondo]

Re: 81 mercruiser 3.0 same as 3.0 chevy?

and i dont see why it wouldn't work,

Ayuh,... Yes,... It'll work...