Mercury 15 hp 4 stroke

[cnlfrey00]

I have a 15hp 4 stroke that sputters in the 3100-3300 rpm range. If I rev the engine and return it to the same throttle position it will run fine for a few minutes and start to loose rpm until it spits and revs back to 3200. The motor runs fine above and below that rpm range.

1999 15hp mercury 4 stroke
Trollmaster throttle positioner.
used as a kicker
ser.# 0t058614
15elrc 4s

Carb cleaned with new gaskets
new coil
new plugs
new fuel line / filter
new primer ball and hose
timing belt in spec.
100psi compression in both cyclinders.
any ideas?

[stingray]

My motor was acting similar, thought had bad gas, checked all the usual suspects. Then all of a sudden a loud pop and it went to normal operating mode. About 15 minutes later, KABOOM! I immediately thought a prop strike but I was in 15 feet of water. No forward or reverse gear, motor is still running. Used the trolling motor to get back to the dock. Got back home, prop would not turn by hand. I removed the lower unit, water pump housing and discovered the bottom of the driveshaft sheared off.