At a loss

[blksmith1]

1990 25hp evinrude, tiller, pull start.
Rebuilt fuel pump, rebuilt water pump, cleaned and replaced needle vale on carb,had a new power pack installed. and was told the coils are ok.
Took it out today. It ran fine until after a long troll ;1/2 hour or so . I throttled up to go back up river,the motor got up to speed fine and then
started to run slower and slower until I was at 1/2 speed or less. Stopped for 15 30 minutes. Started the motor it ran fine.

What could be causing this???
TJ

 

[Cofe]

Re: At a loss

What comes to my mind, is that there is some kind of fuel issue going on here.
Tank Vent ok?
Suction hose in tank may have a screen that is plugging.
Or just the slow trolling speed carbonized the plugs. Just thinkin?

 

[Cofe]

Re: At a loss

Another thing to look at is the WOT timing advance setting. One time on mine the nut retaining the timing advance adjustment came loose. The timing retarded badly.

 

[blksmith1]

Re: At a loss

Thanks cofe I was leaning towards a tank prob.
Will replace the tank. have already replaced the lines in the motor and the lines 2 the tank. New bulb also.Will check plugs new 2 weeks ago.

 

[tashasdaddy]

Re: At a loss

make sure you are not running hot.

 

[kenmyfam]

Re: At a loss

1990 25hp evinrude, tiller, pull start.
Rebuilt fuel pump, rebuilt water pump, cleaned and replaced needle vale on carb,had a new power pack installed. and was told the coils are ok.
Took it out today. It ran fine until after a long troll ;1/2 hour or so . I throttled up to go back up river,the motor got up to speed fine and then
started to run slower and slower until I was at 1/2 speed or less. Stopped for 15 30 minutes. Started the motor it ran fine.

What could be causing this???
TJ

Who did all the work on this ???

 

[Lion hunter]

Re: At a loss

IS it a portable plastic tank? I have never seen a tank go bad other than rust or a hole. If the vent screw is open and the bulb is not sucking down the tank is most likely good and I wouldn't waste $35 on another. You ran for a 1/2 hour on it without any problems.

The symptoms sure sound like a hot motor. I wouldn't try and replicate the issue until you know it's pumping water and not getting hot.