Mercury 20 hp blueband loosing power at high speed

[brett262411]

Hi, I have an old 20hp blue band Mercury. The motor starts fine and idles and at low speeds no problems at all. However when travelling at full or near full throttle for 5-10 minutes engine looses power and gives impression that prop has done a bush. By that I mean it revs high but goes no where. I have had a new bush fitted so this has been eliminated. When I back off the throttle and move off again it is OK and I can continue to operate at this speed but if I increase to full throttle again it doesn't take long to start the problem all over again. I have noticed that revs will start to increase just before problem occurs. This may be another issue but I have an intermittent problem of feeling the current from the engine giving me a zap on any connected metal parts that I touch. This does not occur all of the time and not sure if related. I noticed fuel line had minor leak at tank end and also fuel seemed to be getting past connection where it attached to motor. I have since fixed this but haven't had a chance to test it yet and I notice that the bulb now pumps up a lot harder than before. Not sure if any of these things are related to more problem. Any advice would be appreciated.

 

[chrome dome]

Re: Mercury 20 hp blueband loosing power at high speed

~ 4 yrs ago l had a spun hub replaced on a 7.5 blueband with the original prop, had a little ding in the housing here and there,
put it on and it still spins occasionally now, not like the old hub but enough to be annoying,
not happy Jan,

put a mark on your prop to make sure that the hub definitely isn't spinning, new prop may be an option if it is