RPMs drop after 3 min on force

[19732009]

hi to all i have a 1988 fore 125 and after about 3 or 4 min i go from 5100 RMS to 3900 RPMs and will stay at 3900 to 4100 if i let the boat sit for 4 to five hours it will go back to 5100 for 3to 4 min and so on. i have good water flow and it is not to hot and i can hold my hand on the head and not to hot i have good spark with motor hot or cold replaced all fuel lines and fuel pump motor runs good at idle and half way. could it be jumping out of gear.

 

[Smokepole27]

Re: RPMs drop after 3 min on force

Does it bog down or the rpms just back off?

 

[jaybirddog11]

Re: RPMs drop after 3 min on force

Have you done a recent compression test? Maybe try a compression test when you first fire it up and then after the problem shows up. How do your spark plugs look? Are they very old? My two cents.

 

[jerryjerry05]

Re: RPMs drop after 3 min on force

Sounds like a fuel supply problem.Check the fuel vent then check for soft hoses.The Ethanol in the gas could be clogging up the system.
Change ols/soft hoses and go thru the entire fuel system.J

 

[19732009]

Re: RPMs drop after 3 min on force

Sounds like a fuel supply problem.Check the fuel vent then check for soft hoses.The Ethanol in the gas could be clogging up the system.
Change ols/soft hoses and go thru the entire fuel system.J

yes i have all new hoses and the fuel vent is ok next time i go out im going to do a compression test when the motor is hot.

 

[19732009]

Re: RPMs drop after 3 min on force

Does it bog down or the rpms just back off?

yes it bog down but only if motor is hot