motor runs for 10 mins then revs drop to idle

[apark999]

i have a 83 johnson 15hp longshaft with a new omc 9 x 11 prop, new plugs NGK (equivilent to champion for this model) new impeller.<br />up until today i had only run it with muffs and also in barrel and apart from not wanting to idle very well it ran ok (ish).<br />today i went out and ran for about 10 mins at wot(although didnt feel like wot) on my 14ft dory with 2 men and associated tackle.<br />after 10 minutes the engine began to die gradually losing revs until it stuck at idle revs only just getting us back to shore.<br />i do not know the history to this engine hence the new impeller.gear oil etc.<br />the fuel was brand new today with twc3 oil 50:1.<br />when i got home i pulled the plugs and found the top plug was much oilier than the bottom one.<br />i think i can illiminate a fueling problem as i had pumped the fuel primer this did not change the revs. the fuel vent was open so fuel was not restricted from the tank. i did notice the o ring in the fuel line connector was slightly worn?<br />can anyone give me suggestions?<br />thanks<br />Alex

 

[joaklay]

Re: motor runs for 10 mins then revs drop to idle

Sounds very similar to my 15 hp last fall and after changing gas tanks, problem solved. In my case, it then obviously a clogged intake line in the gas tank as it was fine with the other tank.<br /> In my case, pumping the primer bulb didn't make any difference either.

 

[apark999]

Re: motor runs for 10 mins then revs drop to idle

thanks J. the tank itself is brand spanking new it might be the line needs replacing (or just the o-ring isnt sealing giving vacuum).<br /><br />thanks for your input<br /><br />Alex

 

[apark999]

Re: motor runs for 10 mins then revs drop to idle

any other ideas people? especially as its fouling the top s/plug?

 

[apark999]

Re: motor runs for 10 mins then revs drop to idle

changed the o ring in the connector and it runs ok on muffs but dont know about under load yet.