1992 15hp Mercury - Dead

[michaellawre]

I have a 1992 15hp Mercury outboard Model #OG171558 that was running okay, but suddenly stopped. Upon checking the fuel bowl, I noticed some junk so I dumped it out and replaced the fuel, tank, and lines etc. I still couldn't start the motor so I took it to a boat mechanic who rebuilt the carburetor - still no luck. He replaced the stator, coils and power pack (Switchbox) from a spare motor without any luck. It improved the spark but still no start. I purchased a power pack for $196 that I can't return, based on his recommendation and still nothing. He tested each cylinder and said they each have 90lbs of compression.
I took it home and removed the side cover to look into the pistons and found a little carbon build-up on the top of the pistons and a little piece of a red gasket?? in the top peep hole and a fairly large piece of a black gasket (from the carb??) in the lower piston peep-hole. After pulling the rope to slowly look at the rings and pistons there is plenty of oil/gas coming through into the piston. It has good fuel in the cylinders and a strong spark (with new plugs). Now after spending over $450, it still doesn't run. It seems like it should run but nothing more than a few putts with a little puff of smoke, usually on the first pull and nothing after that. It has always been maintained properly and has been used frequently almost all year around on the Eastern shore of Maryland. Please help! Any suggestions???

 

[G3Joe]

Re: 1992 15hp Mercury - Dead

I just reread your post. You need a new carb.

 

[michaellawre]

Re: 1992 15hp Mercury - Dead

Thank you for your reply. Please tell me how you reached your diagnosis. What would be wrong with the carb? - It was just rebuilt. Is there something that was overlooked or could have been missed? If so, should I take it back to the mechanic who rebuilt it and what should I say to him?
I feel the problem should be something simple and that is probably why I am stumped. I think that if the carb is the problem, we assumed that it was resolved because it was rebuilt and we started looking in another direction. If it is the problem as you say, what approach do I take with the mechanic who charged me $200 in labor and had me purchase the power head for another $196? He has been a friend for many years as we both live in the same water town. I am a bit perplexed as to what he may have missed in his diagnosis and how to bring it back to him with yours. Your Dx makes sense, but I need a little more info to be able to go back and discuss it intelligently.

Thanks for your help!
Michael

 

[G3Joe]

Re: 1992 15hp Mercury - Dead

I don't want to get involved between two friends. Your motor has a neutral safety switch. If this switch is bad the motor won't start. Starting a motor with ether can determine if a carb is functioning or not. Checking the timing of an outboard motor can determine if the plugs are firing at the correct time.

The above is not meant as a diagnosis or advice. Any repairs you accomplish are done at your own risk.

 

[michaellawre]

Re: 1992 15hp Mercury - Dead

Hi G3Joe,

This won't come between friends as we are both trying to figure out the problem. Is there a way to test or bypass the safety switch? The motor was running okay but just stopped and simply wouldn't start again ~ glad I had a paddle! We have tried using ether to start but still nothing. I have been able to get a little chug on the first pull with a little smoke coming out of the exhaust, but this only happens on the first pull and after sitting for a while, I will get another weak attempt at starting with a little chug or two but no start.
Again, I am curious as to how you reached your diagnosis. I am just trying to understand what is wrong or what we missed.

Thanks for your help,
Michael