my 1998 60 mercury losing rpms

[mycool]

my 60 merc will run well for a while then the rpm will drop from 5000 to just above 2500 and will not return to full revs .Will run fine at 2500 .Go out the next day and it runs well for hours and it happens again .Any ideas
thanks

 

[oldman570]

Re: my 1998 60 mercury losing rpms

When this happens you need to heck for spark at the plug to see if one is not firing. The easiest way is to hook a timing light on and see if it lights on all of the plugs. Chances are that one of the CDM modules is bad and dose it when it gets warmed up, the will fire when it cools down. JMO
Oldman570

 

[mycool]

Re: my 1998 60 mercury losing rpms

When this happens you need to heck for spark at the plug to see if one is not firing. The easiest way is to hook a timing light on and see if it lights on all of the plugs. Chances are that one of the CDM modules is bad and dose it when it gets warmed up, the will fire when it cools down. JMO
Oldman570

thanks I will try that