1995 mercury 50elpt4s

[wheelers4life]

I have a mercury 50 hp 4 stroke with carbs. This engine does not have reed valves. I am having a problem with an exhaust leak. When the cowl in on it runs good for a while then it will eventually run like crap. I have taken the cowl off and ran it for two weeks with no problems. I cannot find any black oil spots where it shows the leak. yesterday I took it to the lake with bottle of soap water that I use to find leaks in tires and could not find any bubbles. I set at the dock and plugged in my carb sync gauge and found that the bottom carb has low vacuum and cannot be changed. could the valves for that cylinder be causing exhaust out of the bottom carb and doing the same thing.
Thanks

 

[racerone]

Compression test on the cylinder should be your first step I say.-----Agreed a 4 stroke does not have reed valves.----Even so on a 2 stroke the reed valves have nothing to do with exhaust !!