01 Merc vortec build

[stevekw_3]

Hello, I have a 91 Rinker 4.3 Merc with a busted block. I found a running omc engine from a 88 and switched it out to get thru the summer. Boat has been running fine so far. My plan is to rebuild another engine over the winter and I would like to gain some power. A buddy of mine has a 01 vortec 4.3 out of a chevy pickup with a spun bearing. I plan to take the block to a machine shop to prep for rebuilding, then switch the intake to a 4 barrel one. Being this engine is out of a full size pickup, would the stock cam be ok to use for my build? I've read where truck/rv cams are basically the same as marine ones if so I wouldn't need to buy a new one assuming the one currently in the engine is ok. Also, are there any mods needing to be done on the Vortec heads before putting it all together? Thanks

 

[Bondo]

Hello, I have a 91 Rinker 4.3 Merc with a busted block. I found a running omc engine from a 88 and switched it out to get thru the summer. Boat has been running fine so far. My plan is to rebuild another engine over the winter and I would like to gain some power. A buddy of mine has a 01 vortec 4.3 out of a chevy pickup with a spun bearing. I plan to take the block to a machine shop to prep for rebuilding, then switch the intake to a 4 barrel one. Being this engine is out of a full size pickup, would the stock cam be ok to use for my build? I've read where truck/rv cams are basically the same as marine ones if so I wouldn't need to buy a new one assuming the one currently in the engine is ok. Also, are there any mods needing to be done on the Vortec heads before putting it all together? Thanks

Ayuh,.... Generally, on a rebuild, ya over-bore the cylinders .030" to true everything up,... That means atleast a new set of pistons,...
I'd go with the hyper-techtic pistons, with a D-dish, or inverted dome to maximize the Quench factor for the Vortec heads,...
Measure the Quench to 'bout .043", 'n use whatever volume dish ya need to get just Under 10:1 compression ration,...
Feed by an Edlebrock 1409, you'll be quite Happy,....
The stock cam will work well,...

 

[Walt T]

Don't expect a dramatic increase in power. It's still just a 4.3. Great engine to be sure, just not a real powerhouse.