Mercury outboard problem

30boat

30boat

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My 1990's 2,5 Mercury was gien to me by a friend seized solid and with a completely corroded head.It also showed signs of having had water in the crankcase.I fixed it and replaced both gaskets and seals.Now,after two years of running reliably it started having trouble starting and I found that the plug ws grey with emulsified oil.I've ordered a head gasket and a base gasket but I can't understand where the water is coming in from.Could it be the exhaust?
 
Ingress could be via the lower crankcase seal. If the crank suffered corrosion in the engine's troubled past life, this could well accelerate wear of seal if the area it bears on is affected. The normal result of seal failure is air leaking into the crankcase causing poor starting and erratic running (revs rising independent of throttle position, due to weakening of fuel/air mixture), but there's probably no reason water can't leak in, too, giving the plug issue you describe.
 
30boat said:
My 1990's 2,5 Mercury was gien to me by a friend seized solid and with a completely corroded head.It also showed signs of having had water in the crankcase.I fixed it and replaced both gaskets and seals.Now,after two years of running reliably it started having trouble starting and I found that the plug ws grey with emulsified oil.I've ordered a head gasket and a base gasket but I can't understand where the water is coming in from.Could it be the exhaust?
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Head gasket would be my first suspicion
 
A tip an old marine engineer once told me was if you ever have to change a head gasket on a single cylinder outboard is to flat the head off by rubbing it on a dead flat surface covered with a sheet of wet and dry. Try it you will be surprised at the tolerences
 
Hi Apologies if im teaching my granny to suck eggs. Check for water from source . Ie check your fuel in your can you use to fill your outboard. Petrol is hydroscopic but imo not enough to make a difference to you.
I know myself countless time i have filled my engine up prior to running in a barrel, put the can down next to the barrel started the engine and the wake from the water in the barel spills over the lip of the barell onto my fuel can which in haste i forgotten to put the lid on!!
Now im not suggesting you are as stupid as me but there are endless ways water can find its way into jerry cans.
Steve
 
Have you carried the outboard with the head lower than the prop.

If so any remaining water in the shaft etc. will run down and in through the exhaust port and ***k up the engine.

Always carry small engines with the head up.
 
SAMYL said:
Have you carried the outboard with the head lower than the prop.

If so any remaining water in the shaft etc. will run down and in through the exhaust port and ***k up the engine.

Always carry small engines with the head up.
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That's quite possible actually.I put in the boot that way the other day.
 
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