Mercury 9.9 loses power

[Trebuchet]

I have a Mercury 9.9 2 cycle outboard, about 10 years old. It starts fine and runs well at high speed, but after a few minites it looses all power and drops to about 1/4 speed. If I slow it to idle and troll for awhile it will run again at high speed. The longer I idle the longer I can run at high speed. I changed the plugs and even took the motor in to the dealer for a tune up and they found no problems. Could it be the fuel tank/bulb/hose? Thanks.

 

[gasguzzler]

Re: Mercury 9.9 loses power

try looking for some sort of adjustable friction screw. it may be alittle loose alowing throtle to go back to idle. you may not have a problem,what ever should be holding the speed constant may not be holding it. if you dont follow what im saying let me know ill try to explain in more detail

 

[AndyL]

Re: Mercury 9.9 loses power

Try pumping the fuel bulb when in the fault condition. If it is soft or flattened either the fuel pump needs replacing or the air vent on the tank is not allowing air in to replace the demanded fuel. Borrow another tank and see if that improves your situation as you may have a blocked filter screen in the tank. Post results so we can see if there can be any more leads to follow if that does not cure the problem.

 

[Trebuchet]

Re: Mercury 9.9 loses power

Originally posted by gasguzzler:<br /> try looking for some sort of adjustable friction screw. it may be alittle loose alowing throtle to go back to idle. you may not have a problem,what ever should be holding the speed constant may not be holding it. if you dont follow what im saying let me know ill try to explain in more detail

While the motor is losing speed I have the handle (throttle) turned completely wide open and am holding it there. If I let go it naturaly does rotate back a bit and the speed drops, but I do not view this as a problem. Simply turing it it back to full causes the motor to go full speed, when it is working and 1/4 speed when the problem is being experianced.<br /><br />I think I will get a new gas tank and bulb/hose assembly and try it out.