87 150 Johnson gt rpm

[goodoleboyz250]

First off what are the recommended rpms for this engine at wot and what's the most fuel efficient. Also the rpms quit working when you tilt the motor a certain way what could this be.

[Barnacle Bill]

Recommended RPMs for that motor is pretty broad. 5-6,000. However I think you will find that most people push it to 6-6200 RPM with no problems. Most efficient is probably closer to the 5,000 mark. As for the tach I would suspect a bad connection. Check all the obvious and take the harness connector (under the cowling) apart and check all the pins. Especially the one for the gray wire.

[Scrapper]

I agree with bill. I would keep it 55-6000rpm with average load. Those engines were bad to carbon up. You have to remember even if you don't run wide open, if you prop it too high you'll be lugging through the entire rpm range. Remember boats don't have gears, so you need to be sure you are propped in the proper rpm range. ie...if you are wide open with average load @5000 rpm, that is the lowest point in the recommended range. So if you get any heavier you'll be below it...5000 being low in my opinion anyhow. Even if you never run wide open, if you are lugging at wide open...(lower than recommended range)...you are lugging through the entire range. I would prop it for average load at mid to upper rpm range....then run it with less throttle for efficiency. Just my opinion though.