V6 to v8 mercruiser repower

[MILLER1966]

I have a 1995 ,2359hdtp trophy which is rather heavy and drafts alot it is equipped with the 4.3LX mercruiser which seems to be under powered and has trouble getting up on plane and runs a max 20 knots.July 11 the manfold gasket failed taken the engine out mechanic looked at the engine stateed it would be approx 2000 dollars for repair. So at this point I would rather up grade to a stronger motor and put the money to better use I am thinking of a 5.7 mercruiser but not sure what is invloved ETC,what year motors would work for my boat and do I have to do anything with the drive I have heard that the drive can handle the upgrade any thoughts.

 

[FunInDuhSun]

Re: V6 to v8 mercruiser repower

I'm no expert but I believe the 5.7 outdrive uses a different gear ratio than the 4.3.

 

[TJS]

Re: V6 to v8 mercruiser repower

You can make up the difference in the ratio by changing the pitch on the prop. A 4.3 V-6 is a V-8 SBC with 2 cylinders cut off of it. I am doing the same thing on my Baja project boat.
See link.

 

[robjen1019]

Re: V6 to v8 mercruiser repower

As long as you have room in front of the engine, you should be able to fit it in. As for drive ratio. You should be able to make up the difference with different prop sizes. And if not just put a rev limiter in. Ya you won't be using the full potential of the motor, but you will also have a motor that will last longer if it doesn't run wot all the time. Then when something happens to your outdrive, you can update it at that time.
There is never too much power. You just cant run it up to 7000 rpms.
Have fun