F150 prop & WOT questions

[rmartens]

While I was trouble shooting a recent (fuel injector) problem, I noticed a number of threads regarding WOT RPM and prop selection. The most I have ever gotten is about 5500 RPM before it starts to porpoise as I raise the trim. Although I originally thought this (mid range 5000-6000 RPM) was right, most of the threads indicate that I should try to get to 5900 or 6000. I've looked at the performance bulletins, my hull is not listed, but they all got to or near 6000. So I'd appreciate some education on these topics.

Questions: Am I over prop'd and causing the engine harm? I heard the phrase "makes oil", what does that mean? My normal cruising speed is 4000 RPMs (31 +/- MPH, wife is happier), should I run faster as a matter of routine? I read threads about mounting hieght. I'm in the third hole now and can go one higher. What would be the symptons of it being too high?

I'll be on the water in the next few days and will record some specific perfomance data. I'd rather not spend the $ for a new prop, but..... Any help is appreciated.

Boat specifics
2004 Yamaha F150TXRC (400 hours), 2004 Sea Pro SV 2100 (21') center consloe bay boat at about 1900 pounds, 56 gallon fuel tank, Tee top. Original prop was a 14.5 x 17 M aluminum, replaced with a Michigan Wheel 14.25 x 17 SS. (test run after cleaning injectors, 30 gallons fuel, driver,10 knots of wind, 5500 RPM, no speed data)

Thanks
****Martens

[boats.net]

I like to see between 5500 and 6000 rpm's but if it's porpoising then may need to lower motor on transom or try a different prop to stop it from porpoising and turn up more rpm's.

[joe009]

you could also try a hydrofoil.a lot of people dont like them,but they do wonders for porpoising.get the type that you dont have to drill to mount.i put them on my 20 ft. with the f150 and never took them off.the f150 is a heavy motor.imo you need three things on a boat,tilt,tabs, hydrofoil.all help for a better ride.

[rmartens]

I like to see between 5500 and 6000 rpm's but if it's porpoising then may need to lower motor on transom or try a different prop to stop it from porpoising and turn up more rpm's.

One of Joe009 suggestions is a foil, which I actually have, a wing under the prop on the skeg that my wife made me install as a manatee guard. It may work too well and is lifting, increasing the porpoising. I'll lower the motor one hole and run a RPM/MPH comparison with the 8 other similar boats with bulletins.

What about normal cruising speed? Any significant difference in engine wear between routine 4000 RPM cruising and 5000 RPM+.

Thanks for your advice.