also a 4.3 will bolt up to your bell housing but will require all of it's own marine manifolds dizzy etc and motor mounts will have to be bolted a little further back
If you can source the parts and do more work you can install just about any engine you want
as far as mpg tho the v8 will do nearly as well as anything else if you take it easy on the throttle.... you MIGHT be looking at as little as a 0.2 mpg difference vs even a 4 cyl
for fuel usage reference, many years ago I had a 20 arrowglass cuddy with a 305 (mercruiser 198 hp) and in a day of wot running and very aggressive tubing I could use up the 40 gallon tank of fuel twice.
|