1986 merc 50hp 2 stroke - idles strong, runs horrible.

[Corey Arnold]

Trying to figure out what is wrong with my engine. previous owner said it ran great, like a work horse for the 10 years he had it but it has sat for the last year or so. i believe him.

professional services done in last month -
Full carb rebuild (all gaskets, deep temperature cleaning)
replaced bulb and fuel lines, added inline fuel filter
fuel pump rebuild- all gaskets and diaphrams
brand new stator.

here is the problem - idles and starts great. will throttle in neutral great. will rev out great in gear out of water. once you put it in the lake it no longer will throttle in gear. it bogs/dies, like it is starving for fuel. runs great without demand (out of water), runs horrible with demand (in water).

 

[huntxtrm]

I dont know if this is what your problem is, but it sounds familiar. I have the same motor. I rebuilt the carbs, replaced the fuel lines. And some how, I routed the fuel line from the fuel inlet fitting under the bottom carb, across the shift linkage. Its right under the bottom carb. When i would put the throttle down, it would take off, try to get on plane, then finaly cjoke down and die. The line was in the perfect spot it got pinched, when it was put in gear. Drove me crazy!

 

[Johnb5386]

Going through the same thing with my motor. After wasting a good amount of time chasing a fuel delivery issue, I figured out that it was ignition related. I will let you know what I find out. In the mean time, get it out on the water and pull the plug wires one by one with motor running to see if you have a cylinder down... I did.

 

[Texasmark]

Low speed jets could be closed too far. In the water vs muff running is different because of back pressure on the engine and more hp required to turn the prop in the water. More hp requirement translates to more fuel required. Most engine have 1.5 to 2 full turns out from a soft seat.

Start at 1.5 and open in small increments till it takes the throttle and puts the boat on plane without hesitating. Spark problem would be linkage and timing, or could be dropping a cylinder....on muffs you really can't tell when one is missing, especially with a 4 cyl 2 stroke. A timing light on each spark plug wire on muffs could tell you if all are hitting.