RPMs?

[thoward]

Can a dirty hull pull RPMs from a boat or will "prop slip" increase? What is the WOT RPM for 825 hp 12v71TIs?

The reason behind the question......(60' EB Conv. W/12v71TIs)The boat ran fine when we got it, I never put it to the pins because I wanted to get a feel for her. Well I bent a prop in the mean time. The props were changed and a mechanic has checked her out and changed 1 weak injector. We sea trial her and I can only get 2000RPMs. I had just cleaned the props and rudders but I did not clean the bottom, although it was done last month.

 

[Passages]

Absolutely, bottom fouling, fuel/water load, changes in weight & windage, even trim can affect WOT RPM.

If you are running with a moderately fouled bottom and heavily loaded, tune the engines and take her out for a WOT run. Record max RPM with a phototach down in the ER. If you fail to hit recommended Max RPM, have some prop pitched removed to get it back to where it belongs.

Later, when running with clean bottom and/or light load, you may see loaded MAX RPM go to 50-100 over recommended. This is a good thing as a governor will keep you from over revving. You engines will breath easier too.