4.3 to 5.7 swap

[benzurin]

I bought a 94 bayliner capri 20' in mint condition with a 4.3lx old vortec. I knew it had freeze damage so I got it dirt cheap. I pulled out and it needs new manifolds and it has a crack in the block inside the valley about an inch below both heads and runs about four inches paralell to the heads. I ran it enough to know that there was water coming inside. only has 120hrs and still has cross hatching on the cylinder walls. Can or should I weld the block? Will I gain any HP with new style vortec? Or should I v8 it? would I need a new flywheel? This boat was availble new with a v8. I'm pretty mechanical and have done quite a few swaps in cars but boats are knew to me. This only my 2nd boat

 

[Weirdwalt]

Re: 4.3 to 5.7 swap

Dont bother fixing it. The heads are also very likely damaged. Find a 4.3 or V-8 if you so desire. I assume this is a Merc drive so you might need to change gearset if you go to a V-8. Personally I'd probably swap in a 4.3. Good little motor.

 

[WillyBWright]

Re: 4.3 to 5.7 swap

Most of the stuff from the 4.3 would fit up to a smallblock including the carb (mind your jetting). Exceptions include the intake and exhaust manifolds, and distributor cap and rotor. Your 4.3 probably isn't one of the newer blocks with the balalce shaft. The only thing you may have to worry about might be the intake manifold if you get a rebuilt 4.3. They don't rebuild the older non-balanceshaft blocks and I've seen a few older intakes that would interfere with the shaft. Vortec heads will add 10 to 15Hp. Regarding the outdrive gears, you can usually compensate with prop pitch.<br /><br />One other thing to look at is the doghouse. There may have been different versions for the V-8. And the motor mounts sit a few inches closer toward the bow, so make sure the hull has support there.

 

[Bondo]

Re: 4.3 to 5.7 swap

The motor that's in My boat now,.. Was sitting on a pallet,.. Looking Exactly like Yours is Now........When I 1st saw it....<br />I gave $500.00 for it,..A Complete Mercruiser crate motor.......Frozen,+ Cracked of course.....<br /><br />I drug it home,+ tore it down to See what a Frozen motor with Less than 50hrs. on it Looked Like............<br /><br />Then I called a MachineShop,+ found a used block from a low mileage S-10 pickup of the Same Vintage,....<br />Cost me $100.00,... No machine work,.... Just Gaskets, oil,+ filter.......<br />The cylinders were well within Spec.,...<br /> <br />So,..... I mounted the 2 motors on side by side stands,+ Loaded the Frozen motors Guts into the New used Block,........<br /><br />That was over 700+hrs ago.........<br /><br />This winter I'm adding Vortec Heads,+ a New set of Manifolds,.. Both Intake,+ Exhaust.............<br /><br /><br />There's No Fixing that Block of yours,...... Even IF you Could stop the Water,.......<br />The Deck of the Block, Where the Heads bolt on, Is No Longer Exactly Where It's Supposed to Be,......<br />And,..... When you tighten the Head Bolts,.... That's Where the Cracks Are,...... No Strength Left In It.......

 

[benzurin]

Re: 4.3 to 5.7 swap

I got a line on an 84-89 260hp 5.7 complete with log style manifolds fully dressed. The guy said it only was in water 4 times and wants $1100. What do you think? Should be an easy enough swap right? the log styl manifolds should work, i think?

 

[Don S]

Re: 4.3 to 5.7 swap

No the log style won't work. You will have to get the newer style manifolds, elbows, risers etc. <br />You also need to change the gear ratio in the drive.

 

[Bondo]

Re: 4.3 to 5.7 swap

Originally posted by benzurin:<br /> I got a line on an 84-89 260hp 5.7 complete with log style manifolds fully dressed. The guy said it only was in water 4 times and wants $1100. What do you think? Should be an easy enough swap right? the log styl manifolds should work, i think?

Ayuh,.....<br /><br />And besides the Manifold Problems that Don states,.......<br />That's Probably the next Older Generation of Block,.....<br />The Crankshaft Rear Oil Seal is Different,+ Further Complicates the Issues........<br /><br />What's Confusing is that the 84-89 Doesn't Relate to Anything I know of,......<br />Important Years for SBCs is 79,+ 87.........<br /><br />In the Most Very Basic sense,...... You need a 87 to 95 engine block, or possibly Newer....................<br />Older than 1987 is going to Give You Grief.......

 

[benzurin]

Re: 4.3 to 5.7 swap

I'm working on trying to get the serial number so I can tell for sure. If I change manifolds can I still use my y pipe? Whats wrong with 86 and pervious motors?

 

[Bondo]

Re: 4.3 to 5.7 swap

Whats wrong with 86 and pervious motors?

Nothing,.................Except that they have a 2 piece rear main crankshaft Seal,........<br /><br />That means a Different Flywheel,... Which means a Different,.??.. Which means a Different,..........