4.3 mercrusier short block

[VDrBoom]

which blocks can you use to change out for a mercruiser 4.3 lg vortec. will the chevy s10 or astro block work. being standard rotation, what is the diff. in them.

 

[JB]

Re: 4.3 mercrusier short block

Howdy, VDB.<br /><br />Welcome to iboats. <br /><br />You need to post in the correct forum to get useful answers.<br /><br />I will move this to the Mercruiser Forum for you.<br /><br />Good luck.

 

[WillyBWright]

Re: 4.3 mercrusier short block

Welcome to iboats. Very frequent question.<br /><br />A car motor will work but it won't last. On the other hand, if you wanted to put a MerCruiser 4.3 into that S-10, buckle up and hang on! Just don't get caught at an Emissions Checkpoint...you'll fail the test.<br /><br />Check eBay. There are a few for sale most of the time.<br /><br />In general, MerCruiser uses motors with forged cranks, rods and pistons. The valves are stronger to handle the heavier springs so that you can run it at 4500 RPMs all day long. Then there are the things that bolt on that are specific to marine engines so you don't blow-up your boat or rust parts away in a matter of weeks. Most of the internals are Genuine GM, but top of the line.

 

[Bondo]

Re: 4.3 mercrusier short block

In General, You missed the boat Willy....... <br />All Rods are in fact Forged......<br />The Standard Merc motors are Standard truck engines, possibly with a Merc. spec'ed Cams, Right off the Chevy production line........<br />The Cams are Not of a Radical nature, so Heavy Valve Springs are Unneeded,+ unwanted, due to increased Wear......<br />Unless you get into the HO, or Magnum motors the Cranks,+ Pistons are Cast....... Not Forged.....<br />So,<br />To answer the original Question,<br />The 4.3l has been built in several configurations over the years......<br />If you buy an GM Goodwrench Truck motor for Your Year , <br />You can bolt on all your Merc. acc.s,+ Go Boating........<br />The cam Might be Slightly different, But You'll Never Notice it..........

 

[WillyBWright]

Re: 4.3 mercrusier short block

At least not until you suck in some water and bend some of those forged rods. The cam lobes are timed so that there is less piston down motion while the exhaust valve is open. It's not so much the lift or duration as the timing that makes it a marine-specific cam. There is a short time where both the intake and exhaust valves are open. That's overlap. Marine-specific cams bump that timing toward the exhaust side a tad to prevent water ingestion.<br /><br />Me thinks you missed part of my answer. I said the internals were Genuine GM. But you have your cast GM parts and you have your forged GM parts. MerCruiser opts for the forged ones. Car motors may not. Unless you take the motor apart, you'd never know. Then there's the lifters. Car 4.3s probably have your average run of the mill hydraulic lifters. MerCruiser uses the better and more expensive roller lifters. The list goes on, but you get the jist.<br /><br />I should add that I'm comparing a CAR motor. If you're talking a genuine TRUCK motor, then it'll have most of the things the MerCruiser motor will have except that marine-specific camshaft. I'm not necessarily talking about your average no-frills 2WD S-10 that might or might not have the truck version. If it's a Highway Department or Commercial S-10, it probably has the heavier-duty version. So in that case, Bondo is pretty much on target. In essence, MerCruiser motors are marinized truck motors.

 

[Bondo]

Re: 4.3 mercrusier short block

I'm not here to start a Flame,<br />But,<br />You're spreading Borderline Mis-information.........<br />

At least not until you suck in some water and bend some of those forged rods. The cam lobes are timed so that there is less piston down motion while the exhaust valve is open. It's not so much the lift or duration as the timing that makes it a marine-specific cam. There is a short time where both the intake and exhaust valves are open. That's overlap. Marine-specific cams bump that timing toward the exhaust side a tad to prevent water ingestion.

Exactly..... It's called LSA.... Lobe Seperation Angle......<br />Marine motors can run Only between 109* to 112*........<br />A Truck or RV cam is Well within these #s.........<br />As well as Most Production Automotive motors......<br />Aftermarket cams are a Different Story.......<br />

MerCruiser opts for the forged ones.

False...........<br />Except in the HO, or Magnum series........<br />

Then there's the lifters. Car 4.3s probably have your average run of the mill hydraulic lifters.MerCruiser uses the better and more expensive roller lifters.

False......... Merc. went to the Roller Lifters the Same Time Chevy started using them in Their Standard Production Motors........<br />

The list goes on,

Actually the List is Very Short........<br />Even the Standard Production Motors are using the Composite Head Gaskets Now adays........<br />

In essence, MerCruiser motors are marinized truck motors.

Exactly My Point...... <br /><br />Take a GM Goodwrench Truck motor,<br />Pop in a set of Brass Core/Frost Plugs into it,+ Go Boating................................

 

[Bondo]

Re: 4.3 mercrusier short block

Edited due to a very strange double post.......