Lost R.P.M.s

[groundpilot]

I lost 500 rpm on my 82 Evinrude 150 . Used to run at 5000 but then went to 4500 . Ocasionally the motor would make a slight shutter then the rpm would return to 5000 for a short time . It would then drop back to 4500 eventually . My first thoughts where a fouled plug . No ...that didnt work . Then a new set of wires . Nope again . In fact it lost another 500 rpm after the new plugs and wires . ( Yes they are the correct ones ) . O.K. how about decarb ? Did that too .. Cant find any fuel leaks . The motor runs smooth with no misfiring . No excess water or weight in boat . Is this a problem that could be caused by a failing power board ? Is it possible that maybe one of the coils have gone weak ? Is there a way to test the electrical parts with replacing unneeded parts? The only rpms that are going up now is my blood pressure trying to figure this problem out . Any Ideas would be appreciated .

 

[ob]

Re: Lost R.P.M.s

Compression test will reveal the health of cylinders.Spark test at cranking speed should produce crisp blue spark that will jump 1/2" gap on all plug leads.If that's good ,try adding some artificial heat to ignition components(coils,powerpacks) with a hairdryer to eliminate possible warm component malfunction.Listen for any changes and test for spark again.<br /><br />Next step would be a manual that can outline specific procedure for ohming and output testing ignition components.