With the language differences---------do be aware that if in fact your engine is reverse rotation and that the reversal is not done in the gear box-------the timing marks on the front crank hub will go in opposite directions from the notch-------and the distributor drive gear will be reversed so that the oil pump still turns the correct way---

There may be issue with water pump not flowing water correctly thru engine

spark plug wire location in distributor cap

starters won't interchange

what rpm do you cruise boat at??? On my Sea Ray with twin 454s I usually ran around 3000-3300 at trimmed out speed