Hello Gentlemen, Is it feasible to swap a MerCruiser 305 with a cracked block to a 350 for a little more power? I have to replace the block anyway so for a bit more money and effort I hope to upgrade power output. A 305 works for me but i would like +/- 20% more power from it. It is a 2002 305 190-200 hp version with 2bbl. It connects to an Alpha One MerCruiser

 

 

At least if he swaps it he won't need to buy an anchor

 

LS swap, I hear everyone's doing it!

 

Will the outdrive take more power?

I hear the Alpha is pretty fragile. No direct experience, I prefer V-drive! God Bless Casale.

 

 

They are not as fragile as some would make you believe. Definitely not a Bravo drive though. Think 700r4 vs TH400. Kind of hard to kill a big block Bravo drive behind a small block. Although a few boats had Alpha drives behind the 330 HP 454s in the 80s the Alpha was primarily used with the 4s, 6s and small v8s.

That being said RPM & HEAT are more of a problem for the Alpha drive. They do not like being run for extended lengths of time at or above 5,000 rpm. Even if you do not plan to run it hard, I would recommend fitting the drive with a cooling shower. Also keep in mind that the 3.0/4.3 and some lower power 305s used a lower gear ratio in the drive and that will effect your propeller choice which you will want to reconfigure for the new 350 to keep from over-reving. It IS possible to use a lower geared drive behind a more powerful engine if you make the correct adjustment in the pitch and diameter of the prop.

See this chart for details....
https://www.sterndrivereplacement.co...06/gear-chart/

 

Sounds like a fun swap.

 

If he has a Vortec 350 at his disposal he could pull the truck cam and install the cam from the current 305. The later model 305/350/6.2/6.3 all used the same 395' marine roller cam that is known in the Car/Truck world as the HT383 or Ramjet crate engine cam. Put a set of LS6 springs on Comp 787 retainers and run a set of self aligning 1.6 full roller rockers. Would not be hard to get 330-350 HP out of that setup with a decent dual plane intake and marine 4bbl carb with performance manifolds and risers. Through hull exhaust would just be the icing on the cake. Other option would be to grab a complete MPI system from a 305-6.2 and get the ECM reflashed for the 5.7. Same exact system for all save for the flash on the ECM. Boat would run GREAT with a 300 HP Mag MPI clone compared to the 305.