15hp Mercury 2-stroke hard to start

[blorincz]

I purchased a dinghy with a 2003 Mercury 15hp 2-stroke outboard at the end of the season last year. Only went out a couple of times, but it had no problems starting after a few pulls. Followed standard procedure winterizing the motor (changed the oil, new plugs, fogged the cylinder, etc.) and stored it in my basement.

At the beginning of the season I went up to the local BP station and filled up the gas can with 87 octane and mixed in the oil. The engine started up like a charm on the second pull. Ever since the dinghy has been in the water (almost a month now) it's getting harder and harder to start. First couple times it was 3-5 pulls, then the next weekend I noticed it took 7-10, then the next weekend 15-20. Then tonight I went to go for a ride and it must have took me 30-35 pulls to get it started. Once it starts all is fine, it stays running, runs great, no hesitation, no stalling, nothing. I follow the same start up procedure each time by squeezing the priming bulb and pulling in/out the prime knob 3 times and leaving it out until it starts as the manual recommends.

Admittedly, this is my first outboard and I don't know much about them. I am hoping some of you can offer some suggestions on what the problem might be. Is it possible the problem is the gas? One thing I thought of tonight that I'm not sure about is the gas can has a vent on the cap that you turn to open and close. I have always left the vent open. I am wondering if leaving it open all the time while the dinghy sits in the water is a bad idea? I do cover it, but leave the gas can in the dinghy.

Any help would be appreciated.

 

[Skuza]

I'll stay tuned also. I have an '05 15hp Merc that gave me a little fit last year. When starting it the first time it started on the second pull and then slowly died out. Then it took about 20 pulls after that to get her started again. Ran fine after that but I didn't use it much last season. I'm concerned that the gas might be getting old even though I put stabil in it both years during winterization.

 

[Graham Lorimer]

I have a 15HP Mariner two stroke, so I suspect that it is the same engine.

When I bought it last year (it is a 2003 model) it started OK, but gradually got worse. It got to the stage that when warm, it would flood itself when idling, and even increasing the idle speed was not enough to keep it running properly.

Had it serviced recently and now starts perfectly, first or second pull every time. The needle valve in the carb was gummed up, and it was constantly flooding.

It is important to run the fuel out of the carb when finished using it, and also occasionally run some SeaFoam in the fuel, that is also highly recommended to keep the needle valve and seat ungummed and working properly.

Graham

 

[blorincz]

Overpriming was the problem. I talked to a friend who called a marine mechanic friend of his who said I was overpriming the motor by squeezing the bulb until stiff AND pulling the prime knob in/out 3 times. He recommended giving the bulb one squeeze (or even not at all) and pulling the primer knob out once, leaving it out for a few seconds then pushing it half way back in. And making sure the knob is turned full clockwise to fast idle. I did that and it started it up on the third pull.

 

[Turtlesboat]

One of my projects this weekend was to get my 15hp Johnson 2 stroke to idle smoother. I pulled the spark plugs and dropped the gap from 40 to 30( I read on a forum that it fattens the spark or something to that effect) I did it and now she starts on the first pull every time and idles much much better. Also seems to smoke a little less, but that might be my imagination.

 

[Escapade]

I have 05 15 HP two stroker as well. We also have re-formulated gas!. Had to dump the old fuel. Drain the fuel line. Pop off the cover & sprayed carb cleaner while i was pulling. Eventualy it ran and runs well. Had to adjust the carb a minor turn to hold a low idle.

Its the gas that sits over winter that is scewing up the carb.
Mike