low rpms while in gear

[19seaswirl]

i have a 115 mercury 4 stroke 2003 will not go over 4000 rpm while in gear revs up fine in neutral motor runs fine idle fine start with turn of key just will not get on step have checked fuel system no water have inline fuel/water sep everthing seems fine just will not go over 4000 rpm

 

[Faztbullet]

Re: low rpms while in gear

Did it just suddenly start this problem or has you noticed it getting worst over time? You could have a injector problem or a valve problem. When then last time plugs was serviced?

 

[19seaswirl]

Re: low rpms while in gear

the first two trips of the year motor ran fine then it started to slow down the next 4 or 5 times now will only go about 12 knots pulled plugs out they all look like they are burning fine

 

[CharlieB]

Re: low rpms while in gear

How old are the fuel lines and primer bulb?

Deteriorating hoses can restrict the fuel flow and limit RPM and power.

A simple test, disconnect the fuel line immediately after the fuel pump, pull the lanyard, and crank the motor, watch for a strong pulse fuel flow.

 

[Laotzu]

Re: low rpms while in gear

I had this problem with my 50hp 3 cyl. Turned out it was varnish flakes in the carb closest to the fuel filter (top one in the stack). So at high throttle it was running on 2 cyl.