Water soaked transom

[paintacar]

I have a water soaked transom

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Hi everyone, I have a thunderbird tri-hull, I don't know what year it is, but it is 20'. The boat seems to be in good shape, no hits or anything, however it was sitting, with the front elevated, for about ten years. the drain holes were clogged, and it had about 3" of water in the hull, at the back and in the two rear compartments(center) going from front to rear, I don't know how long the water was in it. I cleaned everything real good, and the fowardmost compartment seems fine, no problems, the wood is good and dry there.however the next compartment back which seems to be sealed off from the outside it has a 6" inspection plate with a gasket, well when I drained it the next day there was 2" of water again in that hole only. I dried it out again and it did not fill up with much again, maybe 1/2 " . we thought everything was fine, so I painted the floor started routing all of the cables for my motor, and when I used a hole saw on the rear deck section between the motor and the inside of the boat (this section is horizontal) for the power tilt lines to run through, I noticed that the board there is soaked, and soft like balsa wood. The floor of the boat is all dry and good. Then I wondered if the transom was the same, so I drilled the 1/2" hole to mount the motor, and the wood in the transom is wet too, and seems to be soft, there is a metal plate on the back inside and outside where I drilled also It is a 1978 merc 150 H.P. boat is rated for 250. I am worried about this, everything I have done so far I fear wasted. I am a autobody tech. and no spraybooth bake cycle will dry anything out, so don't even suggest such non-sense a spay booth uses natural gas and runs about 170 degrees. I am not up for removing any fiberglass or wood in this boat. I have done my share of fiberglass work, and it is not easy to just do it and have it look right, you need to also gelcoat and its not what I am interested in doing. I agree if the foam is saturated in the other guys boat, the only fix is remove it.Is there any thing I should really worry about with my boat, or is there another fix of reinforcing it?
thanks, paintacar
paintacar@comcast.net

[PAR]

The very first thing I check on an older powerboat (more then ten years old) is the condition of the transom. It's rather common to see them rot out, but doesn't mean the death of an other wise good boat. This is your 'motor mount(s)' for the boat and they must be sound.

There's a few approaches to fixing them when they do develop rot and darn near all of them require some fiber glass work. You can try the transom in a can stuff that's going around, but I wouldn't. You can remove the inner or outer skin (save it, you'll put it back when your done) to the area(s) that are rotted (they are, trust me) and remove all the wood that even looks ugly, replacing it with fresh wood or other product, then reattach the skin. Removing the inner skin allows near stock appearance from outside the boat, but is the hardest to do on most 20' production boats.

If this is the boat I think it is, then it's a heavy chopper layup over plywood bulkheads, floors and furniture. The easiest way is to cut the outer skin off the face of the transom, grind back to good wood or replace the whole transom, then goo the skin back on the new transom, fairing and finishing as needed. The fact that plates have been installed on each side of the transom, means someone knew the transom was soft and was trying an easy fix by reinforcing with them. This means the transom has been soft for a while (I told you it'd have rot in it) and hanging a few hundred pounds of motor and cranking the throttle wide open could result in the engine dangling below the boat on her control cables and a big nasty hole where she use to live on the transom. If you do you testing in real shallow water then when she sinks it doesn't have to be raised very far.

It's not a hard job, you can do some reading up and setup a plan of attack. If you follow guidelines used by the industry, you're job could turn out quite well. If you plan well and are prepared, it's a long weekend job, for one guy and a grinder, but plan on two weekends.

[TheFisher]

I recently redid the transom on an older (1978) 22 footer. It took me 3 weekends. The first weekend I cut the inner skin loose and pulled it off. Not an easy task but not impossible either. I also puled the rotten plywood out and began to clean up the inner and outer skins. The third weekend I finished the grinding and cut out the two layers for the transom and put the entire thing back together with thickened epoxy. I also had to do additional glass work but that was also with epoxy. I've gotten good enough with the epoxy that I can mix 24 ounces at a time and not have it kick on me. This is in the 90 degree Florida heat working outdoors.