So I bought a donk that was formerly used in racing to propel a Thundercats inflatable. It's new life with me will just be fanging around on the back of my zodiac in a mix of open and protected waters around the coast where I live. Anyway the oil I was recommended costs $100/4 litres and seems a little overkill for what I want. The other thing is the motor has 185psi compression across all 3 cylinder heads.
So my question is to the people that know about highly modified engines (even better modified Tohatsus) is what fuel octane and oil type should I be using for just general boating?