Logo
FULL SITE MENU

unburnt fuel left in cylinders ????

F

Free for me

New member
92 Johnson 115, New plugs installed beginning of last season under 50 hrs on them Started the motor the other night and It looked like the first time of the season after sitting all winter with the fogging oil. White smoke with a hint of blue. Let it run for a while it finally cleared. Had the boat on the water, same only for a few seconds. but it wont idle correctly it will idle then when I try to put it in gear it will die. WOT ran great 5500 RPMs when I get the boat home and I flush the motor. It had some trouble starting, had to start at 3/4 throttle and the exhaust had a tint of blue like normal. So I take out the Plugs and all 4 had unburnt fuel on them and very brown. I'm also running Seafoam and Stabil in fuel. I know the list of reasons can be long but where do I start?
Thanks
 
check the compression and make sure the fire will jump 7/16 of an inch gap with a real snap with a tester...
 
Is the motor warming up ? ----Thermostats installed ?-------Those motors have a history and require a compression test any time there are " issues " with them.
 
did a compression test, any where from 105 to 125. Spark is good, one of the plugs was fouled, but not sure if it was fouled from normal wear or is there to much fuel getting into cylinder. Is there a way to adjust the oil/fuel mixture?
 
The cylinder with the fouled plug may be running " cool " for some reason.----------Spend some time and $1.00 for a gasket.-------Remove the transfer port cover and inspect piston and rings.--------------You can not adjust the VRO unit to change the mixture !
 
My observations tell me that sparkplugs themselves do not foul up.-------------One must look for the reason the cylinder is " cool " and not producing heat to keep the plug clean.-----Trouble shooting works well, guessing at what may be wrong can get expensive.
 
put in four new plugs started right up. took it out for the day and ran great at the begining, but seems that after the motor sat it was hard starting almost always had to give it 1/2 throttle or more then when went to shift into gear it would stall. Idle was at 500 rpm when in the water. but not sure if the gauge is 100%. correct. it there a RPM gauge I could get to see if it is correct?
 
did the spark jump 7/16 with a tester?..your gauge is probably correct in the 500 rpm reading...thats the reason you are stalling....what do the new plugs look like now?what rpm was the motor turning at idle when you first put it in the water and it was running ''great''?...at this point i would do the fire gap test..if that is ok i would put a timing light on it to make sure you are firing on all cylinders...if the compression is right and the fire will jump 7/16 then your decision is it a fuel or fire problem while it is failing..what you want to avoid is working on the wrong area...this can get expensive and time consuming with no fix..
 
Back
Top