1986 Merc 50hp. Rough idle, dropping RPMs at low speeds, ocassional stalling

[NEStriper]

Hey guys,

I've got an old 50hp Merc 2 stroke that has been running very well for the year that I've owned it. Starts right up every time, no issues whatsoever. A few weeks ago, the idle started to get a bit rough. It would stall when put into gear on occasion, but never enough to be worry-some. Recently, the idle has gotten rougher, with dropping RPMs at low speeds, and even the very occasional misfire (if you would call it that) near WOT. I will be up on plane and it will sound like it's stalled, briefly, but then will keep going like it never missed a beat.

At low RPMs, it will drop RPMs and then pick up again. The only time it stalls, however, is at idle or just in gear. Adding any more throttle keeps her going, although rough.

I did the standard dose of seafoam, 2oz per gallon to the last 3 gallons of gas, but no significant improvement. That is the only thing I have done so far.

Any advice? This is the first outboard I have ever owned, and other than replacing the starter at the end of the season, I haven't worked on them much.

Thanks.

 

[kungpaoshizi]

Re: 1986 Merc 50hp. Rough idle, dropping RPMs at low speeds, ocassional stalling

The 86 has the idle stabilizer right?

 

[NEStriper]

Re: 1986 Merc 50hp. Rough idle, dropping RPMs at low speeds, ocassional stalling

I don't know anything about an idle stabilizer. What am i looking for?

 

[NEStriper]

Re: 1986 Merc 50hp. Rough idle, dropping RPMs at low speeds, ocassional stalling

I've got some more info.

I ran a gallon of gas and a can of seafoam through her, which improved it but did not solve the problem. She would still stall occasionally and once didn't respond to throttle input for a few seconds. That is, I pushed her to near WOT to get on plane and she kept spinning the same RPMs. A few seconds later, she caught up with herself.

Any thoughts?

 

[kungpaoshizi]

Re: 1986 Merc 50hp. Rough idle, dropping RPMs at low speeds, ocassional stalling

I was kinda having this issue, if idle would approach 600-800 it would do ok, but ultimately slowly stumble and die. (only sometimes)
And there were moments when I would push the throttle forward, or the high idle lever, and it would take time to 'catch up'.
So far what I did was, new plugs, plug wires, distributor cap (these made it react better when giving throttle)
Yet my idle would still act funny.

Even though the main battery tested good from Autozone and Walmart, I decided a 4 year old battery might be pushing my luck. (that and it actually started to gurgle a bit when charging, found water levels in it are low, but still replaced it)

My idle issue disappeared completely. I can sit at 500 rpms now with my engine in gear.. (650 is what it should be set to)

I guess ultimately, the engine at idle is still drawing quite a bit of current from the battery, and I think mine developed a short between a couple cores..

The plug wires, plugs and distributor cap (tons of corrosion inside the cap) made a good difference though right away. +300 rpm boost, and the plugs and plug wires really did look absolutely fine.