Motor running at half speed or less at full throttle

[fishbuster]

Have a '95 Mercury 40hp Powertrim oil injected motor that runs fine for 5-10 minutes, then drops to half speed or less at full throttle. Motor not used since 98. Replaced fuel, fuel filter, added Seafoam to tank and cleaned carbs. Still have same problem. Any ideas of what to do next?

 

[DJ]

Re: Motor running at half speed or less at full throttle

Fishbuster,<br /><br />You are losing one or more cylinders. You'll have to catch it in the act and check for spark on each cylinder. Do this by pulling a plug wire-engine running- until you find out which cyl. is not contributing. Make sure you do this with insulated pliers.<br /><br />What do the plugs look like?