Truck engine 4.3L swap?

[cdig]

Hello all, newbie to both the forum and boats in general... Just purchased my first boat only to discover that my 4.3L Volvo Penta is pooched. What I want to know is if I can use a regular GMC/Chevy truck 4.3L engine to replace it if I swap over all the external goodies from the boat motor? Are there internal differences? Ive heard the cam may be different,, and also he head gaskets? What's the diff?

Any input on this would be much appreciated, as I can easily pickup a truck engine vs. the cost of a rebuilt marine engine...

 

[Silly Seville]

Re: Truck engine 4.3L swap?

Welcome to iboats!

There are countless threads here in the forums regarding this very topic. It has been discussed ad nauseum.

But to answer your question quickly...yes, a truck engine will work fine as you've described.

The differences are cam grind, MLS gaskets, and brass core plugs.
There is a much less discussed bevy of information about the importance of bearing clearances and piston ring gap tolerances, exhaust reversion and ignition timing, and a host of other factoids; but that is getting into way too much minutiae for this topic...that is until you are ready to rebuild your truck engine.

See, here is the thing. To replace head gaskets, you must yank the heads. OK, might as well rebuild the heads while you have them off. Next, you want to replace the cam with a marine grind? Well, might as well yank the bearings and replace them too. Well, if you're gonna be in there, why not at least give it a fresh set of piston rings? Well to do that, you should minimally hone the cylinders. To do that, you gotta pull the rods off the crank. Gee, might as well replace the rod bearings then. Oh yeah, and get those pesky main bearings replaced too.

You see where I'm going with this? You might as well rebuild the engine you already have. At least then, you will know that you have a fresh engine ready to perform reliably.

This is all a moot point of course, if you were talking about a crate engine purchase, and not a "salvage yard" engine swap.

A word of advice: If you ARE thinking of getting a crate engine that is not "marine" by definition of the company selling it to you...DON'T tell them you're putting it in a boat. Otherwise, say "bye bye" to any semblance of a warranty.

 

[tpenfield]

Re: Truck engine 4.3L swap?

If you happen to have easy and inexpensive access to a truck engine, and are a good wrench turner, then it may be worthwhile to make the internal part changes. You may even be able to steal the cam from the marine engine. The head gaskets for marine are stainless steel and the core plugs are brass. So, those will need to be swapped out.

So, if you are in the right situation, then it may be worth it. If not, then your shorter path may be to get a marine long block and swap the external parts from the 'pooch'.

 

[SteveMcD]

Re: Truck engine 4.3L swap?

Don't forget to replace the starter, alternator, carburetor and distributor with marine design. Automotive electrical components and carburetors have been known to make boats explode. My AQ255b(gm350) .030 bore and rebuild was about $3500.