25 seapro 2 stroke - Oil/ fuel in water

willisja55

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Apr 16, 2023
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Hi I have a 25hp mercury seapro 2 stroke and I was having an issue with it running very rough around idle last year . I noticed excessive shaking at idle and low speeds that would go away at higher speeds. I noticed the flywheel seemed to be shaky & moving up and a bit not sure if this is something or just normal play. This year I got it out to begin troubleshooting and after running noticed I have milky grey substance coming out the exhaust drains that I assume is unburnt fuel mixed with water. my initial thoughts were head gasket but I did compression test that is showing good. Not sure where to go from here other than removing head to check gasket. Did a pressure test on lower unit and it was fine so I can rule that out. I also noticed I have water spraying out of a little spout at the top of my driveshaft housing which I thought was part of the exhaust separate from the water but maybe I am wrong and this is normal I just never noticed this before( if someone can tell me what that spout is I would appreciate it . I attached a few photos looking for opinions. I took the lower unit off and you can see the milky mixture all through the exhaust
 

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airshot

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What is your definition of good compression? In the pic of the housing with the gray goop running out...is there a ding in the housing or just a funky angle??
 

willisja55

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Apr 16, 2023
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What is your definition of good compression? In the pic of the housing with the gray goop running out...is there a ding in the housing or just a funky angle??
there is no electric start so I got about 120psi on each cylinder with 5 pulls and about 140 psi on each with 10 pulls I assume this is good but i could be wrong. No ding in housing just angle of photo
 

airshot

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Jul 22, 2008
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OK...wow a pull start...you should have a good set of arms by the time you get her up and runnin !!!
 

dingbat

Supreme Mariner
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Nov 20, 2001
Messages
16,074
you think the milky unburnt fuel coming out the exhaust is normal?
Could be.. It’s typically the result of the motor not getting up to temperature.

My 200 HP does the same thing after a day of trolling in cold water. Goes way once water temps raise up a bit
 
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