1982 28' O'Day Thru Hull Replacement

31seahorse · Mar 17, 2015

Hello Chris, (1) We all love a surveyor with a sense of humor! (2) A cheap, plastic caliper will give you the OD measurement of the threaded side of the thru hull and the ID measurement when your boat is hauled out. I wouldn't mess with the hoses very much (maybe not at all) while the boat is in the water. (3) Search for some good backer plate material. I have been happy with 3/4 plywood in some cases, and I like starboard for below the waterline. You might start making some backer plates prior to haulout. (Just make the shape & size you can be sure will fit in the space you have.) (4) Work on the thru deck fittings using your choice of sealant. The butyl (sp) tape is fun to use! (5) Maybe rebed the ports. (6) Change engine oil, fuel filters, air filter, etc, etc.) (7) Tools, tools, tools, The correct ones will make every job easier. The boat should probably have its own set. Note: Tools can't swim. Wrist strap or lanyard may save some. Best wishes, Phil CMCS Cape Coral

njlarry · Mar 17, 2015

Congratulations on your new boat.
Agree with all above. I would not touch the through hulls till you get her on the hard. You can measure theoutside diameter of the mushrooms while still installed but things come soquickly off the internet.
When I replaced mine I used oekemo plywood and gflex epoxy for the backing and sealed with life caulk.
Remember the less robust factory installation lasted 30 years!
Good luck

jibes138 · Mar 18, 2015

I just replaced a couple of mine. I doubt the sizes you mention are that large. My engine intake integral strainer was only 1/2" diameter, so I replaced it with a 3/4" mushroom through hull and a real seacock instead of the ball valve. I used G10 material that you can order from McMaster Carr. It came in a 12 by 12 plate that you can get 4 backing plates from. A saber saw with metal cutting blade will make them round so you don't have pointed edges, and a belt sander smooths them and rounds off the edges. Basically follow mainesail's web site for instructions. My raw water intake for the head was also 3/4. If you have a mask just jump in the water with a ruler and measure them. Getting the OD of the threaded portion of the through hull will probably work as well if you have ball valves. I looked into using those flanged adapters but it is just as easy to install real sea cocks with fewer parts to buy and install. I drilled the holes through the hull for the seacock screws and then epoxied over the heads on the outside once they were tightened up. Then a few coats of barrier coat over that and then bottom paint. Solid as a rock. That Maine Sail gives good advice.

njlarry · Mar 18, 2015

Mine were the same sizes as Jibes. The sizes are also usually printed on the valve body.
I found that the easiest way to remove the old mushrooms was with an oscillating tool inside the hull. About one minute each.
Agree g10 will last forever but marine plywood is so much easier to work with, will out last the boat and is the most commonly used material for through hulls so either should do fine.
the manufacturer used the same goo for bonding the thin quarter inch non marine plywood to the hull and for sealing the mushroom. I prefer an epoxy adhesive for gluing the backing to the hull and a sealing caulk like BoatLife for the flanges. When the valve goes bad you'll need to take it apart some day.
Like it has been said, your boat..your choice.

Euphoria2011 · Mar 18, 2015

Same issue with my 83 model, noticed a leak and traced it down to the fwd seacock which base was rotted and wet, short hauled the boat the next weekend and replaced as shown, pretty bad of me to have let it get that bad

jibes138 · Mar 18, 2015

I used 5/8 G10 but if I had to do it again 1/2 is plenty thick enough. The stuff is like a sheet of glass, has zero flexibility. As I said once installed it is rock solid, I bonded it down with epoxy with glass fibers so it conforms to the hull. I also went a little larger in diameter than what Maine Sail shows to spread the load a little more but also a 12 x 12 sheet gives 4 nice 6 inch circles. Your location may determine how large the backing plates that will fit.

tcwaltz · Mar 19, 2015

I had my '82 O'day 28 on the hard back in October and it was the first time I ever had it out of the water since I've owned it (6 years). I had 5 thru hulls on my boat. 2 x 1 1/2" (overboard and galley sink), 1- 3/4" head intake/AC, 2 x 1/2" scoop style for the raw water intake. 1 is unused, I think it was connected to water cooled refrigeration at some point. I removed and cleaned all of them, made fiberglass backing plates which I epoxied in place then re-bedded with 3M 5200.

I had to replace the through hull for the head because the valve was seized and had galled to the through hull so bad we had to cut it off. I laid up my backing plates using a tupperware sandwich container. I simply waxed the inside of it, cut squares of glass mat, mixed up some resin and kept laying it until it was as thick as I desired. The through hull for the head I made round and about 5/8's thick because it can have alot of pressure put on it. I epoxied that to the hull then installed my through hull. The backing plates I made for the smaller thru hulls were 5/16"-3/8" thick. I also made backplates for inside the transom because I had stress fractures in the gel coat on the boarding ladder. I rolled and tipped and have no issues.

The only other thing I added was an additional 3/4" thru hull for the AC. The PO was sharing the head and AC intake on the same thru hull, less than Ideal.

Stay away from plywood because marine or not it eventually de-laminates. Starboard will last forever, but its slick most things don't stick to it and I found that anything I had a starboard back plate on the locking nuts were not very tight. Great if you need to get something apart, but I want my stuff to stay in place when I'm bouncing around.

I left the Galley thru hull for the next time. Its got a nice blue/green patina but he valve works fine and nothing leaks.

tcwaltz · Mar 19, 2015

I thought about putting a Seacock in but availability and time killed me so I essentially put it back the way it was...I mean its worked for 34 years ya know

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My engine intakes are scoop style with strainers. They are kind of a pain in the ass to clean but I don't have much issue. I know there is a different kind they recommend for sailboats and next time around I'll get those. I have a standard thru hull for the AC and head. I have a filter inside the boat. Easier to clean. I also put a T with a cap in. That way if oyster growth blocks my AC intake (or head) I can just run rod through to open it up.

I have a Yanmar 2GM20 in mine and its similar. Just lift the muffler up as much as possible and clean it all up. I had to two the same thing. The other option is to cap that one off and use the one on the starboard side. I'm almost positive my port one is just in the off position because it used to go to liquid cooled refrigeration and now its just unused.

As far as the AC/Heat goes. I had a 9000 btu unit under the port settee. It was noisy and a pain in the ass to get at. Contact with the hull generated noise throughout the boat. I hated to give up the locker space but I installed it in the top half of the locker behind the head. That allowed me to easily split the output to the Salon and the V-birth and I have a vent in both places. V birth can get downright cold or hot depending upon time of year. I have the compressor dampered pretty well so its noisy but about like a window wall unit. My water pump is down in the port settee mounted by the thru hull. The power control unit is in in the bottom part of the locker. I still have some storage space to hang things so its not to bad.

I'm going to be down in your neck of the woods in 2 or 3 days. My son and I are sailing back to the Panhandle from St. Pete with my father in law.

jibes138 · Mar 19, 2015

One of the issues with using the flanged adapters that Maine Sail recommends with ball valves is it makes the installation a lot taller than just a seacock. The advantage is you can replace the ball valve without removing the adapter. For the two I replaced I went with Apollo seacocks. The engine intake takes an immediate 90 degree turn so I wanted to keep the height lower.

tcwaltz · Mar 20, 2015

jibes138 said:
One of the issues with using the flanged adapters that Maine Sail recommends with ball valves is it makes the installation a lot taller than just a seacock. The advantage is you can replace the ball valve without removing the adapter. For the two I replaced I went with Apollo seacocks. The engine intake takes an immediate 90 degree turn so I wanted to keep the height lower.

I can see a definite advantage to the height. Luckily I have space but I would have a lot smoother turn with a lower high than valve and flange.

jibes138 · Mar 21, 2015

If buying G10 an interesting pricing phenomena. A 6 x6 sheet of 1/2" is 35 bucks and change. A 12 x 12 sheet is 67 bucks and change. For less than twice the price you are getting 4 times the area. You can get one backing plate from a 6 x 6 or 4 backing plates from a 12 x 12. These are McMaster Carr prices. When I bought mine it was shipped the same day and I got it in about 2 days. I only have 4 underwater through hulls so one board was perfect to get 4 at about 17 bucks each. They must vacuum bag the stuff when they make it because it is completely void free. I used a carbide abrasive tool on an oscillating multi tool to rough up the surface really well to bond it to the hull, did the same to the hull. With the three screws holding the seacock in place nothing is going anywhere forever.

1982 28' O'Day Thru Hull Replacement

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