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White smoke from propeller 1997 25HP Johnson

G

G'DayG'Day

New member
I have a 1997 25HP 2 stroke (third hand, doesn't look like its done too much work).
It has a HUGE amount of white smoke coming from the propeller.
I'm not particularly good with machines, but have followed the videos at the top of this page and have done some minor servicing, (carby kit - runs great - and impeller etc, all working fine).
It runs fine, but coughs and stalls every now and then when idling (while smoking badly)
It ran clean with no smoke when run dry with no water, then smoked when I turned the hose on. So I'm assuming water is getting in to the cylinders pre ignition and is being burnt?
I've removed the thermostat - it worked fine, and no blockages.
I've removed the head gasket, it didn't look like there was any obvious leaks or incursion of water.
The centre of the head looks be be slightly concave by about 1-2mm (could this be the cause?) The face of the block seems flat.
I was expecting to see an obviously blown head gasket, but as an amateur it looks OK...
I'm wondering if it could be the pistons? How do I check this?
I'm also wondering if it could be reed valves? (might be the coughing and stalling?) But can't see how this would this cause white smoke.
Any suggestions welcome on what else i should consider.
 
Yes, you're right. I only ran it very briefly to confirm it was water, but I've ordered a new water pump kit to install while I'm at it.
I'm thinking that because there was no loss of power that it's not leaking past the pistons, but I just can't think what else it could be if it isn't the head gasket.
Any thoughts you might have would be really appreciated. I'm just worried I'll put it back together next weekend and have wasted a head gasket...
 
Pull the plugs and look at them, if you have water in the motor the plugs will be cleaned to shiny. If the motor is new to you any chance the motor was fogged before it.was stored. That will smoke extremely white.
 
Thanks, plugs are dirty. I doubt it was fogged and I've run it for several hours so if it was it should have burnt out by now - thanks for the tip though.
 
When you take it apart you will find an impeller that is destroyed.-----Likely overheated the stainless cup of the pump housing too.----Cup may have turned in the pump housing too.
 
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