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2008 50 hp 2 stroke rough idle when hot.

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walleye00

New member
Hey all! I have a 2008 Merc 50 hp 3 cylinder 2 stroke. When I first hit the water, it starts up great, idles in gear and in neutral great. WOT runs awesome for any number of hours. WOT RPM'S are set correctly and I am running about 5200-5400 RPM's when full throttle, depending on weight. When I start to cruise around to locate fish, I start having problems. It will idle in gear and cruise well at low speed for about 15-20 minutes, then it starts to miss, cough, RPM's go up and down, and eventually the motor will die. Then it is hard to restart. Given enough throttle and cranking it will fire back up. Then I will go and open it up at high RPM's and its fine, until I go back to idling. I have been able to replicate the problem in the driveway with muffs on. I let it idle for 15-20 minutes, it gets good and hot, and starts struggling. Plenty of fuel in the line, primer bulb is not flat. Here is what I have done so far. Cleaned carbs, set the timing according to specs, adjusted idle screws on each carb. Carbs are synced. New fuel lines from the tank to the motor. Checked for leaks and can't seem to find any. Running ethanol free fuel. New plugs, rebuilt the fuel pump, replaced fuel filter. I have started to attempt diagnosing electrical/ignition issues. Stator is within Ohm's spec of 500-700 when cold. When hot it has an ohm's reading of 890. Seems pretty high. Is that normal? Does this stator have high and low speed windings? Checked the Ohm's on the Trigger, but according to mercury it is not a readable trigger. Open circuit maybe? I am going to run some more tests tomorrow. I plan to let it get hot and unplug the rev limiter, see if things change. I also suspect that cylinder 2 may not be accurately firing, so I am going to check the spark on all cylinders, need to purchase the tool first. What am I missing here? Any help, thoughts or testing tricks would be greatly appreciated!!. One other thing to note. The other day when I was having issues on the water, i attempted to adjust the idle timing speed. When doing so, with a hot motor, it would not advance past 1000 rpm's. Could this be due to a bad trigger?
 
i have the same motor with the same issues. I've done all those things you have until the electrical/ignition issues. Did you ever get resolution on your motor?
 
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