15 hp runs with choking only

[Oregonbythesea]

I am sorry if this has already been asked but, I couldn't find anything. I have a 1999 Mercury 15 hp with about 15 hours on it. It has always started with one pull until this year. Now, the only way I can keep it running is to use the primer and keep it part way out to keep it running. It has new plugs and I soaked the carb in fresh gas for 12 hours to remove any deposits. Yesterday, I had it running ok for awhile without the choke but if I reved it up, it would missfire. I don't want to take it apart again if it could be something simple. I tried calling the local Merc dealer to see where I might start and I guess you can figure what they said. "Bring it in" seems to be their standard approach and I can't really blame them. However, it would be nice for just a quick hint that I can maybe fix myself. Any help from the forums would be greatly appreciated.

 

[robert graham]

Re: 15 hp runs with choking only

The choking is just trying to compensate for a lean fuel mixture, most likely caused by plugged carb jets. Soaking in fuel won't remove the debris, need some carb cleaner, wires, brushes, remove jets, etc. It's about the only way to get that carb clean, no quick, easy fixes. Good Luck!

 

[ufm82]

Re: 15 hp runs with choking only

So you removed the carb it sounds like? Soaking it will do nothing if the blockage is internal, which it is. Since it runs on the choke but not otherwise we can determine that the main jet is clogged. In order to clear that you'll need to disassemble the carb and spray carb cleaner through every port, galley and passageway. If the engine sits for any period of time the fuel in the bowl will evaporate and leave residue. Over time it builds up until something comes loose and clogs a passageway. The only way to get it out is to take the carb apart.

Once that is done the thing should run fine.

UFM82

 

[Oregonbythesea]

Re: 15 hp runs with choking only

Thanks to both. I was almost sure that was what I would need to do but, I didn't want to take it apart. When I had it out, I couldn't see any way to get the jets out so now I will find a way. I noticed they looked rusty and figured I was in for some problems. I guess there must have been some condensation in there over the years and now it needs fixing. Well, off to work taking it apart.