Won't run after trolling

[Duke1947]

I have a 92 evenrude 40hp. I have only owned this boat since June of this year and it's been out of the water more than not. The problem started with the boat not running at top end. It would run fine at slow speed but when you rev'ed the engine it would drop back to about 50%. I've had carbs cleaned and adjusted and finally had the engine looked at by a pro. He cleaned carbs and rebuilt, re-adjusted everything and replace the fuel lines inside the engine hood. The fuel lines had what looked like tar inside of them and whatever it was was breaking down the rubber and making it Mushy. After his overhall it ran fine at first and was finally a joy but we used the motor to troll and now it misses at much over half throttle and acts like it's starving for fuel. The first time we ran it till we blew it out and again it ran fine at top end. After trolling for about 15 minutes the engine would not run smooth at high rev's and acts like it's starving for fuel, well it lunges instead of running smooth. I bought the pontoon boat to troll with and now I'm being told it's always been a problem to troll with this size motor. What do I do? Fuel additive, 3rd mechanic, new motor???? HELP!!!!!!!!

 

[Lodgepole]

Re: Won't run after trolling

Too much oil fouling plugs? Fuel pump? Still some crud from inside the old gas lines stuck in carb jets? Air leaks to gas line to tank? Lunging sometimes indicates water in gas.
40 should troll OK on a pontoon. I use a 70 on mine and it does fine.

 

[Solittle]

Re: Won't run after trolling

If you paid a mechanic to fix it - take it back. He should guarantee his work.

 

[luckyinkentucky]

Re: Won't run after trolling

If you had a problem in the fuel lines I would start with the gas tank. Is this a 2 cycle engine? If so I've seen some tanks where the owner mixes the gas/oil himself get gunked up with all of the oil residue. This could be your culprit right there.

Also, if you let gas sit for 4 to 6 weeks it tends to form a varnish on the tank, lines, or anything in comes in contact with. It could also be that your engine has set for too long with unstabilized fuel in the lines and tank. This can cause the lines and other mechanical parts it comes in contact with the 'gum up'.

I suggest you do a thorough cleaning of your tank, pump, and lines before fixing it again. Then, if you don't use the motor but once a month I would suggest you add a quality fuel stabilizer to it to keep it from varnishing up. I've seen it in classic cars 100 times. People buy old cars with bad gas in the tank, and have to end up rerunning a new fuel line, rebuilding the carb, and flushing the engine.