[Mike Demo]

I have an I/O 5.7L mercruiser alpha stern drive. This past weekend at full open throttle my RPM was about 400 higher than normal. Speed was unchanged. Does anyone have any idea what may cause higher RPM?

(I am having a tack meter put on it this weekend to see if the gauge is wrong.)

Thanks

 

[Scalawag]

maybe someone snuck into the boat & rejetted the carb?

Sorry about that BUT: maybe the throttle cable was binding up before slightly & your now getting WOT.

 

[Mike Demo]

Humor is OK.

I don't mind the humor. My mechanic got hurt so I don't have him around to look at. Thanks for the reply.

 

[Scalawag]

Mike, that was a little humor { very little} with a serious reply too.

Could be something to do with the carb linkage, or throttle cable as I wrote.
If there was a terrific water temp. drop I'd say that was the culpret but I doubt that one. Also I think if the timing advanced then the RPM's would increase, not posative on that one though.
good luck

 

[seaslug44]

Mike Demo,

How is the condition of your prop? A new nick or even a slight change in pitch could cause an increase in rpms because the prop is getting less of a bite of the water as it spins.

Also, check your tilt & trim and make sure the outdrive is going all the way down into the water.

Finally, were you able to repeat the odd results or did it only happen once?