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1987 Mercury 115 I-6 issues

89PartyHut

Contributing Member
Hello all! I have a 1988 sun tracker party hut pontoon I just purchased. The last few days I have been working on her trying to get her lake ready.

So far I have replaced throttle/shift cables, new ignition switch, new battery cables to motor, new spark plugs, new water impeller. (PO removed oil injection I am premixing 50:1)

So I have been running her on a small 6 gallon external tank sitting next to the motor and everything was going good except for I have a small idle issue I am trying to track down. Anything under 1000 rpm and she will sputter out and die, Looks like previous owner already removed the idle stabilizer. I have read that a bad stator can cause this issue so I have a new one I will be putting in as my volt meter is showing only 12 volts at the battery. Just waiting on the flywheel puller tool. so the idle issue is on hold.

The next task for the day was the onboard tank. It had old gas/water in it and the PO was lazy and didnt want to drain it. I drained out the tank and made sure the lines were clear. I then put 14 gallons of fresh gas at 50:1 premix and a fresh primer bulb.
--- Engine runs like total crap now. It sputters has issues hitting WOT and is surging and smoking way more than it ever has. I also noticed that when I shut it down I can see drips of gas in the water coming from the outboard.

Here are my thoughts. I noticed with the external tank if it sits higher than the outboard the carbs leak gas. The Inboard tank does sit higher than the outboard, is it possible that the leaking gas from the intake side of carbs is causing my issues? I am going to put the small 6 gallon tank back on tomorrow to test this but either way I think I am looking at a carb rebuild.
 
You may be able to just remove the bowls and clean them without a rebuild since it runs good at speed. I am guessing, but I would say the sputtering at idle is from too much gas from trash in a valve letting too much gas in at idle.
Check your plugs for wetness after it dies one time.
A test for this might be to remove the fuel line from engine while running and the engine should begin to idle better as the fuel level drops in the bowls.
 
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