Pulled head, one port clean the other two have carbon?

[trigby]

Hey fellas, I been having trouble with a Mecury 150 efi 1997 model, was running rough, found the temp sender on the port head was bad, changed it out ran better and would stay running ,but #6 cylinder was not hitting very good at all , had good spark 140 lbs of compression,changed injectors , swapped reeds around, still not hitting very good at all on #6, decided to pull the heads and found #6 piston had smut build up as all the others did, but #6 on the head was clean when all the others was smutted up, and I have found no evidence of water on the spark plug after running , the head gasket looked as it was sealed good, could water be entering thru the exhaust baffle/plate getting into the cylinder? if water is the problem why would the piston be covered with smut and not the head side?? puzzles me,Thanks for any help you guys can give , this motors been about to drive me nuts, thanks ,Tim.

 

[Texasmark]

Re: Pulled head, one port clean the other two have carbon?

My opinion, you nailed it....water in #6..BTDT. If it's not via the exhaust manifold, then it has to be via a hole in the block....seems to me....where else would it enter.

Mark

 

[Faztbullet]

Re: Pulled head, one port clean the other two have carbon?

Weak scr in switchbox. Swap switchboxes around and see if problem follows box. Also the inner switchbox (fires 2/4/6) is also the switchbox ECU gets it injector signal from. If piston is carboned and combustion chamber is clean that a sign of fuel wash orincomple combustion due to waek spark or flooding. Water from the exhaust divider would have both the head and piston crown steam cleaned and exhaust side of piston would be cleanest with scuffing on exhaust side of piston.

 

[trigby]

Re: Pulled head, one port clean the other two have carbon?

I think your right Faztbullet, i have not ever seen any sign of water on the plug before,it was flooding out until i found the temp head sensor was bad, now it runs but has a miss, i have swapped the switchboxes around ,no difference, even put 2 good known switchboxes on it, new trigger , swapped stator, injectors , reed plates , coils plugs wires, has 140 psi compression,I have not a clue what is wrong with it,it does gain rpms up to about 2000 or so,when i turn the key towards the off position about halfway between on and off.