Engine Swap 3.0 to 4.3 omc

[Chuckyd973]

hey guys well my underpowered 3.0 finally went! I want to upgrade to a 4.3 or 5.0 but will I have to change outdrives? Ratios in uppers are slightly different but the lowers all have same ratio. Id love to hear from anyone that has done this swap.

Chuck

 

[superbenk]

Re: Engine Swap 3.0 to 4.3 omc

Need to provide more details including what you currently have (Stringer or Cobra)...

 

[Chuckyd973]

Re: Engine Swap 3.0 to 4.3 omc

Oh sorry thought I had that posted in my signature. I have 3.0 omc with a vortec head and 1989 3.0 cobra outdrive. I believe the upper ratio is 21:21 but im not sure how to check.

Chuck

 

[imported_TheMan]

Re: Engine Swap 3.0 to 4.3 omc

OMC is a bit different and I'm not too experienced with them to comment specifically on your situation. However, when I took my original 3.0l and replaced with 4.3L mercruiser I kept the same outdrive. I've repropped and can still maintain my WOT RPM (i actually top out close to 5k vice the 4800). Could probably tweak it a little further but i'm not interested. Basically you should be able to reprop it and be fine, as long as they make an acceptable prop.

 

[Chuckyd973]

Re: Engine Swap 3.0 to 4.3 omc

i was thinking i could just reprop but i believe i would nee dto go to a 14" + sized prop. The biggest prop i think could fit is maybe a 13.75 before it hits the out drive casing. What size prop did you resize to?