what are the fuel requirements for a stock merc. 1998 525sc engine? would 89 octane be sufficent ?

26sonic,

The manufacturer clearly states that they require 92 octane... The initial compression is only 7.5:1, however, if you start spinning them it starts to increase that number and hence the need for 92...

Tnx, Karl

You should use 92 octane, I have twin 1997 525SC in my 43 Black Thunder. You should also rebuild the blowers around 150 hours!

Tony......for you it don't mater. When do you ever put gas in a boat LOL

Just kidding LOL

Yes 92 is absolutely necessary. It is very similar to my engine but I am running higher compression and a deferent cam. The best thing to do with that engine is to either install a intercooler or rip off the 177 blower and install a 6:71 . The 177 works great and does the job but they produces a ton of heat that can lead towards pre detonation. So The higher octane fuel the better. I always keep octane additive with me if I have to re fuel with 89 octane. I went with the 177 because I wanted to keep the motor under the hatch and I found a great deal on it I couldn't pass on. Now I went and got the intercooler I Have to cut the hatch anyway. If I had to build the engine again I would of just went with a larger blower from the start.

I hope all is well , I haven't seen you guys in a while , Let me know if you guys want to go to John's for his super bowl party.

Paul