I just replaced my Volvo Penta V6 4.3GIPBYCCE sterndrive engine with the GM equivalent. The engine runs perfect on land with muffs, but on the water with torque and load on the engine, it backfires and stalls. On water at full throttle only revs up to 2000 rpm and only goes 5 mph. My mechanic (good friend by now) thinks it is a timing adjustment issue with distributor cap. We have the manual. Any suggestions on how to calibrate engine computer and timing to get the engine running perfectly on the water? Thanks for any help.
