Thanks for the comeback people:

I'm not really looking for any major power upgrades - lets face it fuel consumption in a boat is high enough without the recent gas price increases & generally more hp = more fuel unless you get it by becoming more efficient

In my case i inherited a 25 ft boat that needs the transom rebuilt due to rot which means the engine & outdrive must be pulled - stringer OMC outdrive rated up to about 270hp I believe so I have some leaway re power (305 probably 220- 225hp stock) & the outdrive is being rebuilt.

The 305 4bbl hasn't been run for a couple of years but a local marine shop indicates the thrust is within spec but #4 cylinder only at 90 psi - others all 120 to 130, so I suspect sticky valves(?) & plan on pulling the heads doing a check plus a home brew dremel job on the ports to ensure good matching especially for exhaust

The engine is mounted under the rear deck & if I wanted to run the exhaust through the transom it would be possible (as opposed to through the leg & out the prop) but it would really have to be cost effective - what gain vs what cost.

The 350 swap would only be an option if I could find a unit cheap, in good shape with total cost less than a minor tweak on the 305.

Bottom line - would like to find 250 - 260hp, clean up the heads & recam??)at reasonable cost, while still being fuel efficient, & end up with a unit that will be reliable.

Thanks again for any thoughts