Mercury 15hp 4 stroke cutting out at higher RPMs

florida_boater

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Sep 23, 2011
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I'm looking for any help with an issue on my 1999 Mercury 4 stroke 15hp before I have to take it to the mechanic. The motor was having a problem with cutting out coming out of idle and then again at higher RPMs . I rebuilt the carb and replaced the spark plugs. Now the lower end and midrange is great but it is still cutting out at higher RPMs. I just noticed today that when it starts cutting out, water will start spraying out of the upper (what I believe) is an exhaust outlet. It is the port in the center of the motor not far below the cowling. It is not the water pee hole, which is working fine. The motor does not run hot and the oil looks good. It don't see any water and it is not cloudy. Any ideas? I'm not an idiot, but I'm stumped by this.

Thanks alot.
 

Star

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Sep 21, 2010
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Re: Mercury 15hp 4 stroke cutting out at higher RPMs

What RPM does it cut out, Motor has a rev limiter. The motor will drop out for a split second if you are not proped right at 5740 on my 05 15hp. I don't think you should have very much water out of the upper exaust port. How fast are you going when this happens?
 

florida_boater

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Re: Mercury 15hp 4 stroke cutting out at higher RPMs

What RPM does it cut out, Motor has a rev limiter. The motor will drop out for a split second if you are not proped right at 5740 on my 05 15hp. I don't think you should have very much water out of the upper exaust port. How fast are you going when this happens?

I don't have a tach on it so I can't tell exactly but it's only about 60-70% trottle. It starts acting like it is misfiring.
 

Star

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481
Re: Mercury 15hp 4 stroke cutting out at higher RPMs

What you discribe sure sounds like the limiter coming in. Pick up a tach at Northen Tools for $40 it also keeps track of hours on your motor. Your boat should be doing 30mph when this happens, I would guess.
 

florida_boater

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Re: Mercury 15hp 4 stroke cutting out at higher RPMs

Is the limiter something that is could be adjusted or replaced?
 

Star

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Sep 21, 2010
Messages
481
Re: Mercury 15hp 4 stroke cutting out at higher RPMs

No it is fixed electonic RPM monitor to protect it from overreving. First you have to determin that you are really reaching max rpm.
then change your prop to a higher pitch to keep it from reaching it.
do you have any idea how fast you are going. What type of boat do you have.
 
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