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89 50hp Merc

R

rikanit

New member
My 89 50hp Mercury was checked

My 89 50hp Mercury was checked out recently while I had my 9.9hp in for an emergency repair and the compression was 140/140/140 with a 35% leakdown- which I guess explains why it will idle perfect but stall out when I engage the throttle? Although the last time I ran it it would engage after it warmed up from idling awhile. Was told I would probably have as much in the motor as what it would be worth. Can somebody explain to me in laymens terms whats going on with the 35% leakdown and what would be involved in repairing the motor.

I always fish restricted lakes so I haven't even had the 50hp started in over a year and I will have my regular dealer's service department verify what these guys found when I have a chance to take it in. Until then I would like your educated input.

Thanks in advance.
 
"Don't just look at the le

"Don't just look at the leak down numbers. Was it at operating temp, was there any oil on the cylinders, might of had a little rust built up on the cyl walls. 140s sounds good, it run fine.
It is most likely stalling from dirty carbs, bad gas from sitting. Before runnig again have the carbs cleaned. No fuel through one carb means no oil, don't take the chance."
 
"I agree with JB. The 35 leakd

"I agree with JB. The 35 leakdown is obviously not perfect, but almost exactly what you would suspect (25-35) with a 20 year old motor.

The leakdown numbers will be from 0 to 100. Zero is obviously the best, means when the cylinder is at full compression it is losing zero percent of it's pressure over a specified period of time.

35 is about the point where you would consider new piston rings due to wear (or checking for a scored/scratched cylinder). If your leak down numbers are uniform at 35% each, would suspect it is simply the rings getting worn and not forming the best seal possible for that motor. But that number is right on the border..."
 
Thanks guys. I knew you'd

Thanks guys. I knew you'd have the answers as usual. I'm taking it in to my regular dealer tomorrow so we'll see what they say. Its probably about time to trade it in on a new 9.9 anyway since I never use the 50.
 
"If they don't give you a

"If they don't give you a decent trade in price let me know, I'm in the market for a good 50hp. Located next to the Arch, in St. Louis"
 
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