loss of power on merc

[raceraf12]

Recently bought a 1978 merc. 115. Motor runs good for 15minutes then slows to about 5 mph full throttle. Let it set and idle for 45 seconds and it takes of again then problem reoccurs. Oil mixture is 50:1. water is spraying good out of the telltale.<br />Plugs show signs of metal. Am I running to lean and melting down. is it sucking air? Motor was also hooked up to high pressure howe when flushed but water pump seems to be fine please help.

 

[markcv4]

Re: loss of power on merc

racerf12<br /><br />Well it could be a few different things. The only thing I don't like the sound of is metal on your plugs. Look in your cylinders with a flash light and tell me what you see<br /><br />markcv

 

[mbb]

Re: loss of power on merc

I assume motor rpm is dropping to about 1000 rpm if your speed is down to 5mph, thats trolling speed (idle). If motor is still revving relatively high prop hub could be spinning. Metal on plugs sounds very bad, like motor is siezing up when heats up.

 

[raceraf12]

Re: loss of power on merc

pistons look alright. One piston does show signs of a started melt down (flakey) but I think it will be ok if I can get the problem fixed. compression in all cylinders is about 110. just want to get by for a few years on this motor if I can.

 

[raceraf12]

Re: loss of power on merc

could the water pump be weak and not pumping enough except at idle or is this a fuel problem.

 

[JeffSlade]

Re: loss of power on merc

Raceraf12, sounds like a fuel starvation problem to me. Make sure your fuel tank is venting properly and read some of the many posts on fuel problems. May be a simple fix.

 

[JB]

Re: loss of power on merc

Howdy. This is a long shot. Could the thermostat be missing? Several of the Merc gurus around here tell us that leaving out the t-stat causes uneven cooling. Maybe it could cause partial overheat while appearing to be okay.<br /><br />Just a thought.<br /><br />Good luck.<br />JB