Last weekend I was able to get my 496HO's up to 5000 rpms and this weekend I could only manage 4600rpms. This seems to have cost me about 3 mph and I am just wanting some feedback from you on what you think the problem may be. The temperature was exactly the same the previous weekend as was Saturday and Sunday.

-Shoe

It this boat docked? Bottom growth can shave a few mph.

Trim up? was the trim the same?

The boat was not docked fromt the first week to the next and yes the trim was the same. I have no idea??? I have heard about the 496's having all kind of sensors going bad and only allowing so many rpms but I would think that this is not the case at 4600 rpms.

-Shoe

More gas or people on board.
Props damaged
Is your speed via GPS or speedo?

Approximately same gas(within a few gallons) and then later in the day it would have been less fuel this versus last. Same two people on board and there is not a ding on a prop. I may have gained a few pounds in a week but this is frustrating.

-Shoe

Is it possible that you hit the rev-limiter last week-end and the engine is now stuck in safeguard mode - where it operates at 90%?

rev limit does not go to limp mode. before starting the engine turn key to run but do not start, listen for 5 sec. for the warning beep to beep once then if you have a sensor falt ( causing power derating) then you will hear aditinal 2 or 3 beeps after the inital beep. I had a water pressure sensor go out and then a exhaust water temp sensor go out and this is what mine did.

BBB is probably right. If the motor has a fault code in the ECM that is set and not cleared, depending on the code it can put the motor in a 90% only power mode which would account for the possible lost rpms and speed. Have someone or a dealer with a scan tool read the ECM and verify its running a 100% power level. Its probably a minor problem since your not in a fault mode that cuts power to 60% or 10% which is the limp home mode.
good luck,
Ray @ Raylar

Thanks guys and I could understand that if it was just one motor but both at the same time??? I do have a buddy with a lap top and scan tool that plugs into the ECM. I will give that a try.

Thanks,
-Shoe