Mercury power problem Any advise please

[eula30]

Hi, I have a mercury 50hp 1985 4 cylinder 2 stroke nice motor. Motor start and runs good for about 10 minutes after that it lose power on full Throttle. It will still idle really good start very quick and runs but when I go full Throttle the motor doesn’t run like when it was cold. Any advise please

 

[jim dozier]

Re: Mercury power problem Any advise please

What does it sound like when it begins to lose full power? Does choking it when it loses power help or make it worse? Does pumping the fuel bulb when it loses power make it better or no change? Do you have to choke it to start it when its cold? Is thae moter overheating and then losing power? Is there a strong pee stream from the water pump?

 

[Kenny Bush]

Re: Mercury power problem Any advise please

I would check your fuel system, from the tank, through the fuel pump, to the carbs. If everythings checks OK, move to checking the coils and electrical system. Need to start posting more data so we can Negate/Eliminate some problems.

 

[eula30]

Re: Mercury power problem Any advise please

The motor when it loses power its sound good it’s like the Throttle wasn’t in full Throttle. I try choking the motor on full power and it was worst the motor almost goes off. I try pumping the fuel bulb when it was on full power and pump one time and nothing happens, pump twice and it was worst to the motor almost goes off again. To start the motor I have to use the choke every time the motor is cold if I don’t used the choke the motor wouldn’t start. The temperature on the motor is ok, it has a very strong pee when is on full power and less pressure when is on idle.<br />Thank you

 

[eula30]

Re: Mercury power problem Any advise please

BushCat: <br />The fuel system was check and it was ok. What they found about a week a go was 1 cable that it was going to the coils was broken and the wore no spark on sparkplug 3 and 4. Cable was fix and there wore spark on every coil. I went to try the boat on the lake and it ran excellent for about 10 minutes and it start doing the same think losing power in full throttle after that.<br />Thank you

 

[mellowyellow]

Re: Mercury power problem Any advise please

try squeezing primer bulb when it bogs down and<br />see if it picks back up again. if it does, it's<br />a fuel delivery problem. also check and see if fuel is<br />spilling out the front of the carb when you<br />squeeze the bulb as it could be flooding.<br />good luck,<br />M.Y.

 

[jim dozier]

Re: Mercury power problem Any advise please

Sounds like it is still dropping a cylinder. Recheck the ignition and everything they replaced, maybe a wire has come loose. Others may weigh in here with more experience on ignitions but I recall that some have written that some of these ignition parts may work when cool but start to fail as they heat up. You might try using a hair dryer to heat up parts and try to isolate the problem.<br /><br />P.S. Did they "repair" the broken wire or just tape it together.

 

[eula30]

Re: Mercury power problem Any advise please

The cable was completely replace, I also forget to mention that a guy was fixing his boat at the ramp and he told me that, the power pack needs to be replace that the power pack was roted out inside. He didn’t told me what was the power pack so I don’t know what he is talking about.<br />Thank’s

 

[mellowyellow]

Re: Mercury power problem Any advise please

eula, try the simple things and eliminate those<br />first. should not buy parts if not sure.<br />go to bottom left of page and buy a good manual!<br />a simple spark test: when problem occurs, pull<br />1 spark plug wire at a time (carefully) and see<br />if the RPM's drop. if there is no difference<br />after a wire has been pulled, that is a dead<br />cylinder. I don't think a powerpack can rot from<br />the inside, but perhaps I'm wrong <br />good luck,<br />M.Y.