Mercury 50 classic questions.

[churla]

I'm having problems with this late 80's motor and controls. Motor was running poorly. I pulled the carbs off and cleaned and rebuilt them (new floats, screens, gaskets, needle and polished the seat. Ran great - next day - no start. Pulled and cleaned carbs again, ran great for 2 hours - then no start. Pulled and cleaned carbs again, replaced all the fuel lines / primer and new plugs (I don't think the old plugs were bad). Runs poorly if at all. To ad to my frustration the button to disengage shifter to allow a fast idle now does not work. Help. Thanks in advance.

[Valv]

Have you checked pump and fuel tank ?

[churla]

The pump is on the side of each carb and was replaced when rebuilt - I'm going to check into a different tank, although I did clean that out also.

[Valv]

How about electrical. Have you checked for spark on all cylinders ? How about spark under load ?

[fish2live]

hey i had a boat with a classic 50 that i bought from a friends dad and he had the very same problem before he sold it to me he had to have a computer i believe replaced then it ran fine after words. i can check with him and see exactly what was wrong but, i do know it took a few trips to the mechanic to finally get it fixed. the two years i had it before i sold it, it ran pretty good, as good as you could expect from a 86.

[Gus]

I also now own a 81 50hp and the previous owner (my uncle)had to have some computer or electrical part replaced because it was not starting. Funny thing, you could start it by pulling it over by hand with the roped wrapped around the flywheel but it would not start using the electric start. Even though the thing cranked over fast and furious sometimes it just would not start. The merc mechanic that fixed it said that this was a "common" problem. Sorry I don't remember exactly what the part that needed replacing was. But the motor has never run better than it has since then. You may want to try and start it with the rope after turing it over for a bit with the electric to get the gas flowing first. Usually all the motor took was one pull of the rope and it would fire off when it wouldn't start with key. I seem to remember some description of the problem that the started motor was leaching too much power from the ignition system because this "part" failed not allowing the motor to start. Thus by not using the electric start and pulling it over by hand the starter motor was not leaching power and it started right up.

Sorry I have no idea about the fast idle button though.

Hopefully my random rambling will help, othewise I just killed 5 minutes at work. Good luck.

[churla]

Thanks for everything guys. I'm almost at the point of throwing in the towel. I used a different tank, on land w/the muffs on, ran great. Waited a few hours started again, ran great. Started the next morning all good. Put back into the lake and NO %&)#@) START.

[BIG DS]

Don't give up yet. You have a spark issue. The reason it will start and run with the muffs is there is no back-pressure on the exhaust. When it is in the water there is back-pressure and that raises the compression slightly. The slightly higher compression is "blowing out" your spark. The most common problem with this era motor is the stator goes to (can't say it). There is a updated stator available through your Mercury dealer that will fix your problem for good. In very few cases the coil went bad also, but that is not very likely. If you wanted to check for spark under load, the spark should be able to jump a 1/2 inch gap and be easily visible, mostly blue. If you have a hard time seeing and it is mostly orange, there is not enough power there to spark under compression and thus will not fire the motor. I could go on and on, but the rest is best left for a qualified mechanic.