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87 35hp Mercury

J

JonnyBoats

New member
Hi so I recently went through a no spark issue. And now have regained spark after replacing the old trigger and stator. The trigger had bad wiring and the stator wasnt giving enough power on the meter.

Finally regained spark! But the top spark is perfect and really strong (I shocked myself) though the bottom spark is somewhat weak. I so far have replaced the entire ignition system with mostly OEM parts except the coils and Switchbox. I’m kind of stumped. It runs but takes a minute to start needs to be choked out and given throttle. Warms up and then can idle but kinda rough.

Any Ideas? Compression is 140 both cylinders and New plugs and coils “New/Working” stator and trigger off a parts motor and an Amazon switch pack.
 
Unfortunatley, these engines had other mechanical issues that often show up as a poor or inconsistant idle regardless of how many parts you throw at it. The problem was these engines wore out the center labyrinth seal in the reed valve assembly causing internal leaks between cylinders. Typically it was caused by the engine being over propped and causing the crankshaft to wobble or actually break. The only way to find out is tear it down and measure the clearance between the crankshaft and the reed valve labyrinth should be .002"-.003" . I had one the measured .030" would not idle right. Point is, just be careful how much money your throwing at this engine.
 
It has the original recommended prop. I made sure to get the specific oem pitch prop. It does seem to be timing or ignition related. Almost like it is running on one cylinder. It can idle just at 1/4throttle. I have a video of it running not sure how to get it on here. I took it out hoping it was just a carb isssue like I messed with an adjustment when taking it off. I used a phone speedometer and with the throttle lever pushed to full it only would push us 6mph. It would idle rough afterwards. Occasional stall at WOT. Would that be symptoms of a bad reed valve?

I don’t plan on throwing a lot of money at it. I just want to make it through next season so I can save up for a newer 50hp. It ran just fine before I touched the carb and ever since I’ve had issues with no spark and now this.
 
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