6cyl in 4 a 8cyl

"I have a 1985 chris craft sco

"I have a 1985 chris craft scorpian, it had a 5.7l 260hp omc. I have a complete 6cyl mercruiser with the outdrive, can I just take the 6cyl, and put it in the place of the 8cyl?? I realize I may loose some speed, but wouldn't i get better gas milage from the 6cyl??"

"This is just my opinion based

"This is just my opinion based on having trucks and boats both with 4.3v6, 5.0v8 and 5.7v8 and theres nothing like a v8.
The first few years of the 4.3 v8 had an inherent
vibration so they started production of the motor with a balencer shaft and this helped a little bit. How long, big, heavy is your boat and how did it perform with 5.7L?"

Keenan.
The hole in the ster

Keenan.
The hole in the stern may keep this from working. If you have the 800 drive forget it. The hole in the stern is to large for the merc to fit.
You could put the 6 into the OMC but you need a new exhuast tube for the engine to work with the OMC unit and a manifold for the engine if it is a in line 6. If it's a V6 then you may get away with just the engine manifolds.
The mounts should work and the engine coupler as well.
It may need the gear set changed depending on what it has now. I'd think a new prop with a lower pitch at the least.
Also is there enough room under the engine cover and in front of the engine compartment to allow for the longer engine if it's a in line engine?
As far as fuel use goes you may not see much of a change if at all if the V8 was calibrated right. The 6 is going to be working harder than the 8. It may do better on fuel if it is a inline 6 rather than a V6.
There are just too many things that can affect this type of change to say yes or no on the fuel use.

Must realize it takes basicaly

Must realize it takes basicaly the same amount of energy to produce the same result (boat on plane).

This project very similar to wee-weeing into the wind!


Bob