Hi John,
I have the same arrangement on Grace (1983 M17 #400) and my
drains failed. She lived in saltwater for 10 seasons before I bought her
and corrosion took the thru-hulls out. I read the copper pipe
replacement advice but 1-1/2" hose won't fit on 1-1/2" pipe (1-1/2" pipe
is 1-1/2" inside diameter). The original thru-hulls appeared to be
thin-walled aluminum tubing glassed into the hull. I believe the tubing
was primarily the form around which the glass was placed as well as the
attachment point for the flexible hose. I chose to replace them with
1-1/2" stainless steel tubing which has a 1-1/2" outside diameter and is
much sturdier than aluminum. I ground out the remnants of the aluminum
and glassed the ss tubing in place. I am confident that no amount of
banging around will damage my new thru-hulls (at least not before the
hull itself would fail). I think the original thru-hulls will last for
the life of a fresh water boat (but I would still recommend checking
them every few years), but they can and sometimes will corrode to the
point of disintegration in salt water. I think I'll add some in line one
way valves this winter to the hoses to eliminate the occasional backup
of water into the cockpit. Your drains may be just fine but it would be
prudent to pull the hoses off this winter and check their condition.
Good luck.
Mark Dvorscak
GRACE
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