Through-hull anomalies

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Feb 15, 2009
18
Oday 28 Manhasset Bay, LI
I'm revisiting this site for my old pal, Lew, who owns an '83 (I think) O'Day 28. He's still on the hard and took a look at his hull, which he'll have bottom-painted this year. He was surprised to see a suspicious circular pattern of close to a foot in diameter encompassing his old knot meter. I went to take a look and it is indeed odd. I looked inside and the unit appears to be of non-metallic construction. The installation seems secure, and I have no clue as to why this circular pattern, seen in layers of bottom paint, might form.

Yet even more disturbing is the look of the fitting next to the knot meter. This boat once had a saildrive, and for some reason it was removed long ago, to be replaced by outboard propulsion. I assume a custom cap for the saildrive was seated in place of the missing engine. I further assume it was attached with the aid of the very bolts used to secure the engine. Presently, however, all bolt heads are rusted off and the cap (if indeed that is what it is) looks pretty time-worn. Which made me consider the possibility of catastrophic failure. I will say that from the outside the cap seems to be robust.

These are the ruminations of someone with little specific knowledge about saildrives, or exotic corrosion in general. I have some photos which I've posted here, showing the knot meter "crop circle" from the outside, as well as from the inside, next to the saildrive "cap".

Thanks in advance for any diagnosis.
Paul
 

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Feb 26, 2009
716
Oday 30 Anchor Yacht Club, Bristol PA
I'd say it's a "hard spot" due the reinforcing of the hull for the SD. Grind off the paint and see if the core is wet would be my suggestion. Hope it's not wet!
 
Feb 15, 2009
18
Oday 28 Manhasset Bay, LI
I'd say it's a "hard spot" due the reinforcing of the hull for the SD. Grind off the paint and see if the core is wet would be my suggestion. Hope it's not wet!
Thank you, Denise. I scraped and wrapped on the hull around the area and it seems in robust condition. I'm turning my attention to the saildrive "cap" now. Anybody know how those things are attached?
 
Jun 2, 2004
1,952
Oday Day Sailer Wareham, MA
I have the installation instructions for the OMC ZEPHYR, I was hoping that it would give a clue as to what kind of material the engine mounting flange is made from, but it really doesn't. The ZEPHYR engine was mounted using bolts through that flange and into nuts attached to the underside of the flange. The bolts do not (based on the OMC instructions) penetrate the hull. I wonder if the cap was fiberglassed over the outside of the engine mounting housing.
However, that old saildrive housing is still a huge liability! When the saildrive was removed the whole setup should have been removed and the hole glassed over with a patch inside and out. THat is a big hole if the "cap" were to come off and would sink the boat in record time.

As to the area around the knotmeter, it looks to me like someone tried to fair the thru-hull to reduce drag and what we see is the result of the build-up of filler around the flange. Maybe, maybe not.....but it is a theory!
 

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