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RPM increase since last use

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deyjason

New member
I have a 2005 Mercury xr6 150hp. Had it out about 2 weeks ago and it ran fine. Normally it runs 6500 (est) rmps WOT, today I noticed from a dead stop when I put the throttle all the way down it was pegging out. Tach only goes to 7000 so I would have to guess it was 8,000-8,500 rpms. It also stayed at this elevated level on plane. So from there I just putted along at around 4,50o rmps to get back to the dock area. Other than that I just had it at idle which I believe was also elevated rmps but can't remember. What are the possible causes? What should I check?
 
That motor should have a max 5600rpm. Your tachometer has issue. I don't think that motor can go pass 6200 at anytime.
 
There are switches on the back of the tach so it can be set for different engines. Pull the tach out, mark the switch settings, spray a small shot of WD-40 into each switch and move them back and forth several times. Clean any corrosion off of the terminal points. If that doesn't correct the over tach it may need replaced.
 
I looked at the data tag and it does say max rpm 5600 but I thought it meant that the max recommended rpms was 5600. I will try to clean the tach as suggested; I am hoping that this is the issue and it is not a motor issue. Thanks for the feedback.
 
Jeff,

I've had this boat/motor for a year; bought it used and this is the first one I've owned. I don't know how to tell how high the motor reved; this was the reading on the Tach but when it happened, I didn't want to continue to run it if it was indeed reving that high. Without knowing a difference, I played it safe? How would I tell if the motor reved that high? In the end, I guess your point is to check the hub as well to make sure it is not slipping/spinning. Thanks.
 
Hummm... I suggest you take a knowledgable boater for a ride and ask him/her. It's pretty opbious if the hub is slipping to one who has experienced it. (Think of a car with a burnt automatic transmission.)

Alternately, you can verify a slipping hub by removing the prop and marking the inner hub and prop with a deep scratch, then running the boat. If the two marks 'moved' then it's slipping.

Jeff
 
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