Where can this water be coming from?

[kaliona]

If it freezes due to improper winterization it can push it out. The plug can also rot out due to age, don't think a 165 has been made since about 1981 or 1982…

as mentioned would look if it is coming off the head gasket or I had a cracked head on a merc 150 which is the little brother of the 165, back of head of it gets hot Can crack. Had a stuck thermostat tapped it when it opened nice cold Memorial Day lake water (50 deg) hit it ….

have you owned it since new ? would be surprised if a 45 yr old boat has never been hot…

I've owned the boat since 1993. I live in an area that hardly ever freezes. The few times the temps have dropped to 32 degrees I've always opened the pet **** and drained the block just in case. I'm keeping fingers crossed its just a leaky core plug and not the head gasket or cracked block. I'll have to wait and see what the shop finds.

 

[04fxdwgi25]

Maybe get a cheap borescope (a bluetooth / WiFi one can be had on Amazon for cheap) and have a peek back there while running. Won't show a leaking core plug behind the flywheel, but will show a core plug on back of head or a weeping head gasket.

Maybe you can get your phone camera back there to see it, too.

 

[Scott Danforth]

you are correct, a micro USB or a USB-C borescope is about $8 from amazon.

however it wont show the core plug in the block behind the flywheel. because there isnt one on the back of the head

Unfortunately this is one of those times where you need to pull the drive then pull the motor