U4ICK

I modded my '99 502 in my Prowler last summer but really did not get a chance to run it that much. Installed Dart Pro-1 heads, Cometic S/S head gaskets, IMCO aluminum exhaust, complete MSD ignition, San Juan FWC and had the ECM upgraded. I had been running 89 Sunoco but when I filled it up for the winter (backup fuel supply for my generator) I mixed 50 gallons of 93 with 50 gallons of 89.

Not sure how true this is. Had a friend of mine tell me he put 93 Sunoco in his Scarab 29 with T350 MAGS. It would run but would not go to WOT RPM. His mechanic told him that Mercruiser has a knock sensor and if it does not detect some knock, the ECM will detune the engine thinking there is a problem. Said he put 89 back in it and no problem.

Just curious what you guys think is the best fuel for the motor.

ED

GO4BROKE

iTrader: (1)

Never heard the knock sensor story,unlikely, but possibly could be true. Stock black motors are happiest with 87. You need compression and timing advance to require higher octanes. Unneeded octane lowers horsepower due to poor fuel burn. Higher octane is harder to burn, therefore less prone to detonation. That is an overly simple defination, but it works.

U4ICK

Thanks for the feedback. I will try 87 this Spring. Got 100 gallons of 93/89 mix that I need to burn off first. If the motor does not perform well with the 87, then I would guess the knock sensor is doing it's job.

Ed