I just viewed a recent "Post" dealing with the same issue.
I've got a 1987, 21' Seville cc, w/ a 165hp Mercruiser 470. I imagine the same principles apply, but, does anyone else have anything to add specifically re: my engine....??
Before the season ended last fall, I'd experienced coolant loss, (that WAS NOT), visible to me anywhere externally. I only discovered coolant loss when I checked the coolant level in the engine before & after running the boat. I noticed that often the level had dropped significantly after an ordinary amount of use (1>2 hours), & sometimes, overnite when the boat was not in use, but simply docked at the slip.
The boat was winterized at the marina, and has been sitting since late Sept 2011.
I went to inspect the boat the other day, & noticed that there was a small amount of green coolant clearly visible in a small amount of bilge water, forward of the engine compartment..
The engine has NOT been running at all.....just sitting in storage on a trailer.
Can anyone help explain to me how the coolant might have leaked out ?
