Johnson sometimes running rough

Jeff23

Cadet
Joined
May 1, 2005
Messages
17
Hi All--

I apologize in advance for the length of this post. Wanted to do a clear description for you.

On my 16' McKee Craft, I have a 1998 50-hp Johnson two cylinder, which I recently bought used from a reputable local dealer. It ran fine for a couple of days then began to run rough. I run it from a portable tank only, fresh gas, 50:1 oil mix. I stopped to check that the connectors were on right, engine still ran rough at high speed.

I took back to dealer, who cleaned out the carb at no charge and said there had been a fair amont of gunk in it. The engine than ran fine for a week or so. Two days ago I was coming in through a tidal rip that sometimes produces fairly big standing waves, and the portable tank got jarred up and down a bit (I have since secured it with webbing). I slowed down, and once clear of the rip, the engine ran fine but sounded like it was sucking fuel and ran rough when I attempted to plane. Almost like one of the cylinders was missing.

Yesterday I bought a new, larger diameter fuel line (3/8") and a new six gallon tank. Started the engine. Ran fine at the dock but wouldn't run up like I believe it should when I rev it up in neutral (Don't have a tach). Ran ok at low speed, then died again when I put the throttle forward to get up on plane. There was occasionally a chirp from the control box--sounded like one I sometimes hear when I push in the key to choke it. No owner's manual came with it, so I've sent for the Seloc manual. Not familiar wth the chirping sound--is it a fuel restrtriction warning?

I tied it to the dock and went home to get my trailer. Came back about a half hour later and I decided to try running it one more time. Low and behold, it started right up and ran great at full throttle--boat planed right off. Ran up and down the river and harbor, slowing down, starting and stopping the engine, planing off then running slowly. All fine.

So what now? If it ain't broke don't fix it? Look for whatever was ailing it before I left it at the dock to get my trailer? Was it just some air in the line that is now cleared? This is driving me crazy, since I don't want to take my family out if I there's something wrong with the motor (I have a 5hp kicker though)

Could this be something I am doing? Since I don't have a manual I'd be grateful if you all could tell me what if anything I'm missing. And any other advice as well

Thanks, and again sorry this was so long.

Jeff
 

da_ardvark

Seaman Apprentice
Joined
Jul 31, 2007
Messages
39
Re: Johnson sometimes running rough

Cleaning the carbs is not the same as rebuilding them. This is what I would recommend. The kits are cheap, the process is simple and straight forward, and you virtually eliminate the possibility of running lean and ruining the engine because of lack of lubrication.

My engine was running good sometimes and not good others. Rebuilt the carbs..........Engine is now perfect.

Good Luck

Denny
 

Solittle

Fleet Admiral
Joined
Apr 28, 2002
Messages
7,518
Re: Johnson sometimes running rough

I would add a fuel filter/water seperator to the fuel line if you don't have one already.
 

Jeff23

Cadet
Joined
May 1, 2005
Messages
17
Re: Johnson sometimes running rough

Ok thanks, will do. I take it I need the filter even though it's a portable tank?
 
Top