engine running at low rpms

[shanedog]

I have a 2008 22' bentley pontoon I just received from in-laws. It has a 2008 60hp merc bigfoot efi 4stroke on it. I just put on a 14x13 prop and when i took it out on water, rpm guage is reading 3500 rpm at wot. Manual states it should be at 5500-6000 rpm wot. Boat initially had a 14x10 prop on it, but it was so dinged up that I replaced it before I put it in water. I do notice that motor doesn't respond to throttle increase until about 1/2 to 3/4 of way into travel of throttle control. Does this sound like throttle cable maybe stretched? Also, could this be fuel related? Boat has a large built in tank, and they did not run the boat much. Boat was half filled with fuel when I picked it up, but fuel could be from last year. I am going to call them today to find out. Any help is greatly appreciated. New to this site and boating in general.

 

[EGlideRider]

Re: engine running at low rpms

Stretched cables are extrememly rare and I doubt if you have a fuel issue. The cable may need adjusting but looks like that would have been noticed long ago. You should first go back to the 14X10 prop which is about right for your setup. If the R's still aren't sufficient, then I would take it to competent mechanic to diagnose the problem. You should also inquire about the past maintenance history to keep the engine healthy.

Welcome to the forum. Please let us know the solution to the problem.

 

[shanedog]

Re: engine running at low rpms

Thanks for the input. I have a 14x10 prop ordered and am going to try that. In talking with dealer, he stated that rpms for that motor and setup should be 4500 to 5000 wot. So, looking at that, i'm not that far off. if i go back to 14x10, that should bump me up to around 4000.

 

[Jeep Man]

Re: engine running at low rpms

I have the same motor and the sweet spot is 5500 -5800 rpm. 14x11 is the recommended prop. 14X13 should not have dropped it that much. Maybe check your tach for accuracy. My experience has been 5100 with 14x13, 5700 with 14x11, and 6200 with 14x9.
As to the cable, remove the cowling and watch the cable on the starboard side of the motor. Have some one move the throttle slowly. Ensure it moves the connection lever correctly. There is an adjuster there if it needs it.