need to replace Mercruiser engine

[dalewalt]

Hi All,

I have a question that'll probably make quite a few of you cringe, but I'm on a tight budget and need to do this as inexpensively as possible.

I have a 1989 20' Celebrity with a Mercruiser 5.0/Alpha One. The engine's bearings are shot (confirmed by an auto-mechanic friend). As I'm sure you're aware, the block itself is just a GM 305 block.

The cheapest fix I've found so far to replace the engine is ~2800; a local marine repair shop will get me a used engine, rebuild it, and install it. Not too bad, but money is tight right now, and I don't see being able to part with almost three grand anytime soon.

Mechanic friends (of the non-boating variety) think I should be able to get a GM 305 engine from an auto junkyard, put my current intake/exhaust manifolds on it and be off-and-running.

Is this possible? Can I just swap the intake/exhaust from my Mercruiser onto a generic GM block from an auto?

Does anybody have any other ideas?

Thanks for any ideas/suggestions.

 

[wire2]

Re: need to replace Mercruiser engine

Well, yes, it can be done but there's a bit more to it. Look for an engine from a truck, not a car. It's designed for more low end grunt. Or else switch your cam & lifters over to the "new" block. Mark the lifters so they go back on the same cam lobes.

But you need to move lots of other bits over as well, to make it "marine".
Have a look at the items listed in this post from today;
http://forums.iboats.com/showthread.php?t=403273

 

[dalewalt]

Re: need to replace Mercruiser engine

Whew, quite a bit. Thanks for the reply wire2.

 

[Big Boat Bay Buster]

Re: need to replace Mercruiser engine

Looking for just a truck engine is not necessary. My '87 Mercruiser 350 cross referenced to a Corvette, Iroc engine of the day--2 bolt mains. Just use the camshaft from the boat engine.
How is the rest of the motor. If its good, I would consider a repair. 9 times out of 10 its the rod bearings, not the mains. You could lift the engine, drop the pan and replace the oil pump and the bearings. put it all back together in one day. Probably do it for less than $150. Get the parts from your local speed shop, racing quality real cheap.
Chris

 

[dannyual767]

Re: need to replace Mercruiser engine

Looking for just a truck engine is not necessary. My '87 Mercruiser 350 cross referenced to a Corvette, Iroc engine of the day--2 bolt mains. Just use the camshaft from the boat engine.
How is the rest of the motor. If its good, I would consider a repair. 9 times out of 10 its the rod bearings, not the mains. You could lift the engine, drop the pan and replace the oil pump and the bearings. put it all back together in one day. Probably do it for less than $150. Get the parts from your local speed shop, racing quality real cheap.
Chris

The only thing wrong with this idea is that you still don't know (and certainly haven't fixed) what caused the rod (or main) bearing(s) to go bad. If it is a rod, that big end may now be out of spec and only replacing the bearing may be a temporary fix before it goes out again. Not only that, but you'd better take a good look at what that crank journal looks like as well .

I fully agree with using your current engine's camshaft and lifters. Make 100% sure that each lifter goes back onto it's respective cam lobe or you will wipe the cam and lifter out. This only applies to flat tappet cams/lifters and not rollers.

 

[Bondo]

Re: need to replace Mercruiser engine

Mechanic friends (of the non-boating variety) think I should be able to get a GM 305 engine from an auto junkyard, put my current intake/exhaust manifolds on it and be off-and-running.

Is this possible? Can I just swap the intake/exhaust from my Mercruiser onto a generic GM block from an auto?

Ayuh,... Go find a junkyard 350 out of a Truck,...(87 to 95)
Change out the coreplugs to brass,...
Bolt on ALL of the accessories from your 305(carb, alt, dist, manifolds, etc)

Then go boatin' with your new Free Horsepower....