Not obtaining full RPM

[searay495]

Hello everyone. Took my 2004 420 Sedan Bridge out yesterday and decided to "open her up." I have Cummins 6CTA's. I was alone on the boat with quarter tank of water and three quarters fuel. I think I'm supposed to reach 2680 RPM and was only able to obtain about 2460 RPM's. Any thoughts?

 

[Ididntdoit]

End of season slime/growth? Did it reach full RPMs in the spring? If not, are you overpropped?

 

[Riptide III]

Don’t know what full rpm should be. But I do know fuel filters will also cause that

 

[searay495]

If I remember correctly it did reach 2680 in the spring, and the fuel filters are clean. Maybe it is growth on the bottom.

 

[ASH]

I often bump the cruise 1 / cruise 2 switch in the dash while cleaning.....Make sure it is in the middle or "off" position to attain full RPM

 

[Henry Boyd]

It’s most likely a boat condition situation. Last spring when I brought ours down from winter storage in NH with fresh bottom paint, tuned props (and before we moved all the other stuff in) we hit all of the Boat test numbers for fuel consumption/rpm and hull speed. Last week tried it again and not so good. So the condition exists with our Volvos as well.

 

[Jeremygavin]

From splash day back at the end of April till now my fuel burn as slowly gone up 1gal/hr on each engine and my load at 2000rpms when from 71% to 74%. I am under propped so I can still reach WOT rpms even with the higher loads. I put 110hrs on the boat so far over the course of the season so the boat didn’t sit too much. It has been the same each season, It is amazing how much the scum on the bottom slows you down.

 

[searay495]

All valid points. Thank you for your help!