1996 Mercury 115 Wont Idle ???

The engine overheated due to weed obstruction in the water intake and it shut off. Cleared the weeds and tried to start it, but it wont idle. The engine starts and runs fine with a little throttle, at about 1000 RPM. Any suggestions ???

Re: 1996 Mercury 115 Wont Idle ???

UPDATE:

I havent had a chance to do a compression test but i did check for spark and all four cylinders have spark, however the two lower cylinders dont seem to be firing. After firing I removed the spark plugs and the two lower one were wet with fuel.

Re: 1996 Mercury 115 Wont Idle ???

Compression Test Completed:

Cylinder # 1 - 130
Cylinder # 2 - 115
Cylinder # 3 - 125
Cylinder # 4 - 125

Re: 1996 Mercury 115 Wont Idle ???

It wont because they only run on the first two cylinders at idle low compression
on #2 have to have machined.

Re: 1996 Mercury 115 Wont Idle ???

Like Joe said, your 115 is a 2 + 2 motor, only the top two cyl's carbs have idle circuits and pass enough gas to fire at an idle. the botom two are just along for the ride until the throttle is opened, then the bottom carbs start passing enough gas for them to fire.

It is entirely possible that # 2 Cyl has been hurt by the overheat, scoring the cyl wall and loosing a bit of compression.

You can remove the exhaust plate and inspect the cyl's/pistons for scoring to determine the extent of the damage now,

OR, you can run the engine for a few hours then retest compression and hope that the cyl recovers some compression.

Depending on the extent of damage to the cyl wall tho, #2 may require a new piston.

There is still Hope. 115 psi is till enough for a cyl to fire. After a bit of run time you may try readjusting the idle mixture on # 2, a quarter leaner/richer to see if it makes any improvement in the idle.