I've got a 350 Mercruiser inboard with a closed cooling system.
We have such high municipal water pressure that the garden hose blew out the
gasket of my raw water flow sensor.
Next time I'll install a shut off valve near the end of the garden hose so I
can stop the water flow when the engine isn't running.
Anyone seen this problem? It also made one of the raw water filter
connections leak. Double clamped too.
I don't think you ever get that much pressure on the cooling system with
normal use.

Also, I used 1 part anti freeze to 3 parts water for the closed cooling
system. This was based on advice from a guy at Holt heat exchangers. I
trust him completely. Any opinons on this anti freeze ratio?

Other wise it started right up as soon as I remembered to open the fuel shut
off valve....