Mercury 7.5 Comet

Hi there all. Could someone out there please advise me of the correct Surface gap plug for my little outboard. Also is there anyone who has a copy of the manual or a link to where there is one on the www. i am using this motor on a 8 foot punt it seems to lack the full compliment of Hp as it will not get onto the plane. What do you do to decarb the motor. Seen it talked about but not sure how to proceed. How important is the condition of the propeller and are there any recommendations out there.

Re: Mercury 7.5 Comet

Dont know your year model so check this out and you can look it up. www.clugplug.net

Re: Mercury 7.5 Comet

The year of my outboard is 1977 - 1978. Found the plugs @ Ngk same plug listed for several years of that motor. One other thing I forgot to ask. Does anyone have a picture of the rubber moulding used around the motor cover. I think it is P shaped but have no idea of the dimensions. Thanks.

Re: Mercury 7.5 Comet

hedly, mercury has a product for decarbonizing called power tune . it is sprayed thru the carb ...follow the directions on the can. it's good stuff.<br />

Re: Mercury 7.5 Comet

You still need a serial number to determine year and porper plugs and thier gap.<br />If it above #5226934, you need Champion <br />#L77J4 gapped .040"<br /><br />SR# to 4397536 WITHOUT PHASEMAKER IGNITION Use Champ L77V.These are gapless plugs.<br /><br />PHASMAKER equipped models use Champ L78V gapless plugs.<br /><br />Do be sure to have the proper plugs,as serious damage can result.<br /><br />Now, about the prop,and the fact that the boat will not plane... If you can get full RPM from the engine,and it still wont plane,there is no doubt the hub has spun-out in the prop. It will cost 20-30bukz to have your prop rehubbed at a prop shop. This engine should have no difficulty planing an 8ft hull.