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  1. #1
    Platinum Member Platinum Member 26sonic's Avatar
    My Boats:
    boats, cars
    Join Date
    Feb 2001
    poughkeepsie, ny, usa

    stock 1998 525sc

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

  2. #2
    Platinum Member Platinum Member Thunder1's Avatar
    My Boats:
    34 Fountain CC
    Join Date
    Mar 2001
    Boca Raton, FL, USA

    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

  3. #3
    Registered Black Thunder Boat's Avatar
    My Boats:
    1997 Black Thunder SC
    Join Date
    Aug 2001
    Lake Norman NC
    You should use 92 octane, I have twin 1997 525SC in my 43 Black Thunder. You should also rebuild the blowers around 150 hours!

  4. #4
    Team Dysfunctional Charter Member Hot Boat's Avatar
    My Boats:
    28 Scarab, Blown 850+ Hp
    Join Date
    Jan 2001
    PUTNAM VALLEY, Hudson River Valley
    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.


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