I have a 04 225/ho I could be wrong but it seems that after about 3 hours on new plugs I develop a miss at idle then if I go thru an extended idle zone when going up on plane the miss will continue and then quit after the r's come up, next idle zone it will be fine until I idle for a few minutes then the whole process will begin again,its like its loading up? thanks for any thoughts
05064973 04
One possibility is that the motor is not warming up enough at idle. You can use an infrared temp gun to see if the heads are a minimum of 140 degrees. Many times sand, shell, weeds, etc. will lodge in the thermostats and cause "cooler" running temps. Remove the t'stats, and inspect the seals also.
The pressure relief valve on the top aft of the motor can also leak internally keeping the motor from warming up. A quick check, after determining that the t'stats are OK, is to pinch off the hose attached to the thermosat housing area on each cylinder head. If the motor then starts to warm up more, then have the assembly replaced, chances are you are still in warranty. A knowledgable dealer tech would know how to check these things out.
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A Technical troubleshooter possessing more tools than talent !
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