1984 Mercury 25XD rough idle

[wbussenger]

Bought used - Did all these items but still very rough idling - at high speed runs great: clean fuel, new fuel filter, new plugs (NGK BUHW) manual specified, cleaned all wiring - grease was turning gray under connector covers, set low idle speed according to manual and adjusted - manual talks about throttle shutter and reed value - any ideas??? what is compression number for test?

 

[WillyBWright]

Re: 1984 Mercury 25XD rough idle

Welcome to iboats.<br /><br />First the compression...they're primarily rope start motors, so the compression will be toward the low side. Depending on the gauge, I'd look for something just over 100 psi and no more than 10 to 15 psi difference between the two.<br /><br />It seems popular to flip reeds around when people take them out. Bad idea. If they're forced against the reed block by spring tension, the motors start hard and idle rough. This might be a possibility. It's better to have a few thousandths of clearance than to have tension holding them closed.