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Mercruiser 140 30 missfiresteam

N

nic_surry

New member
"I have a erartic running engi

"I have a erartic running engine,missfiring on anything over tickover,have also noticed what I consider excessive steam comming out of the exhaust,I have removed riser and manifold no obvious signs of a crack or hole and gaskets OK,have checked compressions and all OK,I don't know if riser has ever been replaced can these be crack tested,I have all ready replaced nearly all the electrical components but I am sure I have water incress but would appreciate some help"
 
"What are your air and water t

"What are your air and water temps? Cold air and water will give the illusion of "excessive" steam. If your spark plugs are normal in color and all the same, all may be well except for bad wires, cap, rotor, water in fuel, etc. If one or more of the plugs are clean as new then water could be getting in possibly via the intake manifold. Do the basic tuneup and see what happens. Check the fuel for water."
 
"Thanks for response,I have al

"Thanks for response,I have already replaced coil plugs,plug leads,condensor,dist cap,rotor arm,low tension lead,have stipped carb and replaced all gaskets,have replaced head gasket no signs of gasket faliure,refaced surfaces of ruiser and spacer as these were found to be not flat,checked for any obvious cracks or corrosion,put it all back together and it still missfires,the engine does not need to be warm to missfire ie;crack opening when hot.have tried a set of illuminating caps that go between plug and lead and these all illuminate when running,it is winter in UK but I feel there is excees steam coming out of the exhuaust when run on muffs definately moore than previuosly(Like a boiling Kettle)Today I have removed the Risser,inlet/exhaust manifold inverted these and filled with water no signs of a leak/crack,also filled cylinder head with water no signs of water in ports.The missfire started at high revs and within 1 hour had progressed down to 1500 RPM and above.I really am baffled now"
 
"PS have also tried a remote f

"PS have also tried a remote fuel tank with fresh fuel.I think I have iliminated all the electric side(Also replaced Distributor)I think it must be water getting into inlet side but how I do not know.PS compressions checked today and all OK,Also ran water down the exhust and it flows a treat out of prop,just a thought but has anyone experienced problems with the lifters?"
 
"i have been helping a fiend o

"i have been helping a fiend on his boat same condition i dont know if this applies to your boat but i found distributor condensor slightly loose and caused all type of missfiring for us, replaced screw with a larger one and problem solved. as for steam issue unless you have teltale signs of water in crankcase milky residue on dip stick, oil filler cap vent tube i doubt of water concern, good luck: rodney"
 
You could try another condense

You could try another condenser since they can readily fail right out of the box. Perhaps it's time to investigate the timing chain for play. Remove the dist. cap and put a socket and breaker bar on the crank pulley. Rock it back and forth a few centimeters. If the dist. rotor has any delay in movement the timing chain may be ready for replacement since you already replaced the dist.
 
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