nige Posted June 16, 2004 Share Posted June 16, 2004 I've got a 1999 Johnson 25 hp 2-stroker, 2 cyl. with a single carb that has a bad case of the cough/shakes. I do all the regular maintnence including winterizing. My problem began with a rich mixture put through when i lent the boat to my friends dad. He put in 30:1 cocktail while it requires 50:1, so there was an abundance of oil on the plugs and in the chamber. I've run about 2/3 of a tank of good mix through it. Now when i give her full throttle, it floods itself and dies. I can only operate at about half throttle. It feels as though the motor wants to go by surging for a moment after you decrease the throttle. The carb operates normally as i just adjusted the linkage. I've cleaned the plugs and reinstalled them, but the hesitaiton persists. I'm reluctant to take it to the marine mechanic as he charges 69 bucks and hour! any ideas on what it could be? I thought it was dirty plugs but no. Maybe the a/f ratio? i have no idea... Link to comment Share on other sites More sharing options...
jdub Posted June 16, 2004 Share Posted June 16, 2004 Check the choke, I know it sounds simple, but that is the only thing I can think of. You may just want to chang the plugs just for the heck of it anyways. Link to comment Share on other sites More sharing options...
nige Posted June 16, 2004 Author Share Posted June 16, 2004 yeah, i fiddled around with the choke to get it going, but it still gets the same trouble. I don't want to run the motor any more as I may burn out the tops of the pistons Link to comment Share on other sites More sharing options...
kbreitwieser Posted June 16, 2004 Share Posted June 16, 2004 look at the bottom of the carb, it may have a drain plug... there may be oil trapped in the bottom causing the engine to still have a bad mixture. Also, if he used an old fuel tank there may be sediment trapped in your inline fuel filter, or even water trapped in the bottom of your carbs. Definatley try new plugs, and make sure both cyl. are getting spark. Also, don't change your fuel/air mixes too much, see if you can get your hands on a service manual so you can check the specs on what the adj. should be. General rule of thumb is 1.25-1.5 turns out from the needle being seated. Good luck, and if you still are having problems PM me and maybe I can help more, I used to be a boat mechanic a few years back... Karl Link to comment Share on other sites More sharing options...
MatterHorn Posted June 16, 2004 Share Posted June 16, 2004 do a compression test to eliminate that problem... most marine motors that I had that stumbled like that were due to low compression... Link to comment Share on other sites More sharing options...
87pathy Posted June 16, 2004 Share Posted June 16, 2004 check your fuel filter as well, I had a similar mystery with my weed eater, i ran some thick gas through it (cause I had it) and a little while later it started doing the same thing. First I changed the plug, no go, then i checked the choke cause it was acting the same way yours is. at the end of the day, i took the fuel tank off and the little filter inside had some oil and gunk on it. i cleaned it off and away she went. Link to comment Share on other sites More sharing options...
nige Posted June 17, 2004 Author Share Posted June 17, 2004 cool, i'll check the filter and look for that carb plug Link to comment Share on other sites More sharing options...
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