repowered i/o
 

Have a 1989 v20 with a 3.7 four cylinder has any one repowered thinking of going with the 4.3 v6 hoping to get more speed

I'd go for a 5.7.

If i go to a v8 i have to change outdrive with the v6 i can use same drive gear ratio

The 3.7l engine will be tough to beat for speed and economy. The 4.3l I highly doubt will give you anymore top speed, but will add some more weight in the stern. The 3.7l imho really was a great powerplant for the v20. The new v6 that mercury is building may be an interesting option to consider, but being a one off for just mercury and being so new, I'm sure its fetching a premium price.

The 4.3 v6 wot is 4400 to 4800 rpm and I could turn a bigger wheel so I think I would get better performance

4.3 motors are expensive for the power you get, Id go str8ight to a 5.7 or at least a 5.0 V8 The 4.3 may show better horse power, but the torque of the 3.7 or 5.0/5.7 v8 shows in a boat


BTW, Ive got a used 5.7 TBI complete engine that has a rod knock from low oil pressure. Its complete, manaifolds, harness, injection, etc... It was a salt motor. $500. It will need to be gone thru, but everything is there

WOT RPM's don't mean anything for speed or being able to turn a bigger wheel. It's all about torque and where it makes it. A good example is my neighbor has an older SEARAY 270 cabin cruiser. They made that hull from around 84/85 till 92, and it was offerred with both the 3.7L and 4.3L for a few years. It's a HEAVY pig with an EMPTY hull weight of almost 7K lbs(no engines, no nothing), and from what I found the 190HP 3.7L topped out at nearly an identical max speed as the 205HP 4.3L's did, but the 3.7L guys say they get better MPG, and sit slightly higher in the stern from less weight. It's your money, but my bet is you won't go any faster, just be lighter in the wallet and heavier in the stern.

i swapped out a 4.3L for an MPI350 mag. 165hp to 300hp.
makes the boat so much fun to drive. coming off plane to cross big boat wake? open it up on the other side of the wake and your up on a plane in 2-3 seconds, no more "hey guys can you come up front"? 43mph (gps) top speed, 2.7mpg at cruise (33-3500rpm).
yes it sits low in the back, but i also have two type31 batteries, a bravo leg and a 9.9 4 stroke kicker and two downriggers in the back end. I needed trim tabs to help porposing.


at the end of the day im very happy with the swap, would do it again