[Surfistar]

Mariner 40hp 2stroke 2cyl. 1999Hello,I have a strange problem with my outboard engine.Idle is sometimes very rough and it stalls.Especially when I go into gear it stalls.Hard to start again if stalled.Everything works fine above idle speed and in gear with gas.- petrol is new- carb is cleaned - compression is ok- idle speed is checked- pumping primer bulk doesn't helpWhat could be the problem?For me it seems to run lean so I adjusted the idle mixture screw for half turn out to get it richer. Now the mixture screw it is about 2 turns out. With this adjustment the engine runs better in idle and in gear BUT after 10 minutes of full gas (engine runs fine) I got back to idle. For the first 10 seconds in idle it runs good but then idle got rougher and rougher and it stalls. Restart is hard and I have to give much gas, when I go back to idle then to get into gear it stalls again. The problem seems to come from the lower cylinder as when I unplug the upper cylinder with running engine it stalls but when I unplug only the lower cylinder it doesn't stall and continuous in rough idle.My dealer thougt that the engine is sucking air and wants to remome a oil seal in the shaft. But I think that there should be petrol coming out if this seal should be worn. But there isn't any petrol coming out.I recognized some water (really not much) inside the engine after full gas. Could this little bit water be the problem?Any ideas are appreciated.Thanks a lot.The lower cylinder seems to be the problem as when I unplug the upper cylinder it stalls but when I unplug the lower one it runs further very rough.Rough Idle Engine stalls in idle and in gearHello,

[studlymandingo]

Are you getting spark to the lower cylinder? Also, check the plugs and note if there are any differences in color of the electrodes, or variances in the amount of fuel/oil on them.