15hp Evinrude, Any Ideas?

My 15hp evinrude started acting up on me while i was out fishing two weeks ago. It would take off to top speed at full throttle and after about twenty seconds, it would die down. While it started to die down, if i left the throttle at full throttle, it would die completely, but if i cut the throttle down, it would run fine at low speed. Give it a second to run at low speed, open the throttle fully again and it would take off but after twenty seconds, it dies down again. I thought it was a carb. issue so i took the carb. off and cleaned it. Put it back on and the same issue(takes off but after 20 seconds, dies down). I had never changed the spark plugs since i have had the motor so i did that and still the same issue. I then went out and bought a new fuel line from the tank to the motor, checked to make sure fuel was getting to the carb. and it was. I did not replace the fuel pump but inspected it and it looks clean. One small detail, I went out last weekend and while on the water, disconnected the fuel line from the motor to burn out all the fuel out of the carb. After i did that, the motor ran constant speed at full throttle and did not bog down but it was not running as fast as normal. I then thought that there may be water in the tank so i drained it. I left the top off the motor on accident this past spring and it rained heavy but i used the motor and it worked great several times after that up until now so i dont think that relates to the issue. At full throttle the motor feels like its kicking(almost like the prop is catching up with itself or it gets a better spark for a second. At this point there is no wrong answer. Any ideas or suggestions are greatly appreciated. Thanks David

Re: 15hp Evinrude, Any Ideas?

Try pumping the primer bulb when it acts up and see if it helps, maybe you have a fuel pump going out.

Re: 15hp Evinrude, Any Ideas?

I agree with above. The one other thing...your sure the tank is venting? Best of luck. Rick.

Re: 15hp Evinrude, Any Ideas?

Be sure to check your coils very closely for hairline cracks.This can cause all sorts of grief and seem like other issues.Been there! had it happen to me!

Re: 15hp Evinrude, Any Ideas?

Good spark on both plugs and the motor has good compression. Took the boat out fishing with my father yesterday so he could see what it was doing and the boat ran perfect. I have not changed anything else on the motor since i posted this thread. I filled the fuel tank up completely before going out so i'm going the see if the issue starts again at lower fuel levels. If the issue does occur again, im going to change the fuel pump. I'm assuming with lower fuel level, the fuel pump has to work harder because there is not as much fuel pressure to help the fuel pump by gravity feed. Is this assumption possibly correct.