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Thread: Setting rev limiter on 7.4MPI to 5000 RPM, any comments?

  1. #1
    I have a 7.4 MPI in my boat and the current rev limiter or governor is set at 4200 RPM. I am wanting to turn the motor to 5000 RPM. Has any one done this and had any luck with it or have you had motor damage? I had the same motor in a tube chassis rockcrawler with the rev limiter adjusted by FastChips to 6500 RPM and the motor would set there and take it ALL DAY LONG with no problems. I know that the motor has a cast crank and cast pistons, but was just wanting some feed back on this since the boating thing is new to me. Any comments would be appreciated.

  2. #2

  3. #3
    I turn my 454's 5400 rpm . 3/8 arp rod bolts , cast cranks , for short periods of time with no problems. Both engines have thermostatically controlled oil coolers ... temp never goes over 220 degrees.
    Have you changed the cam or anything else ? The stock cam may not make any more power @ 5000 rpm.

  4. #4
    Liberator TJ1984
    I grenaded the cast pistons in a 7.4 Merc. shortblock , was told they were only good to about 5200 and that was why they failed ( was running close to 6000) rest of the components could handle theRPM's >not the cast pistons .... someone else may add to this

  5. #5
    I was just curious if anyone else had done this to one of these boat motors or not. The one that was in my s-10 was stock excelpt for a zz502 cam and a set of Harland Sharp roller rockers and we turned it 6500 all the time and even sometimes until the manifolds were glowing red. It has been running this way for over two years and not had any problems. The motor in my boat is all stock with the exception of a aftermarket flame arrestor. I am wanting to turn it to 5000 to pick up a little more speed is the idea.

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