Mike wrote:
I have an old Mastercraft inboard ski boat that I need some help with
fixing. Where the shaft of the prop goes through the hull there is a
metal plate. The edges around the plate were leaking and it was
sealed with silicon. I cut out the gobs of silicon that were there
and found that the plate sits in a 1/2 inch trough in the fiberglass
hull. When the silicon was removed I can move the plate fairly easily
by hand, even lifting it up slightly. I replaced the existing silicon
with Goo marine sealant. I let the sealant set for 24 hours then
lowered the boat back in the water. My little leak turned into a
gusher.

How is this plate supposed to be secured to the boat? Do I just need
to do a better job with silicone? Is there some adjustment that needs
to be made to hold the plate on better? Should this have done over
with fiber glass?

I put photos of the plate and problem area he www.lyonsland.com/BoatLeak

Thanks for any help.

--Mike

Being no expert on that fitting, I'll make a guess. There may be
fasteners through the hull from the bottom, or, it is bonded to the hull.

Either way, the fix is the same. Remove the fitting, clean out all old
"goo" and replace through hull fitting using new polysuphide (sp) sealant.

You cannot EVER fix a leak by putting goo around the outside. Silicone
is a bad choice for below the hull fittings. Polysulphide has a life
span of 20 years. +/- How many of our boats are that old?

You may not nave to remove the shaft if you can slide the fitting aft
enough to get good access to the surfaces and rotate the fitting enough
to clean it properly.

My opinion here is that anyone who uses the term "goo" does not
understand the difference between the proper sealant for each job.

Jim