Possible to replace small sections of a transom?

[AMG08]

I have an issue that I hope I can get some advice from you all on.

Im fairly certain that my transom wood is wet in a few small areas where there are thru-bolts going through. I have noticed over the course of a couple months 3 spots that started out as small pinholes. I drilled out the corrosion, filled the holes, and went on with life. Well the issue came back in the form of more seepage from the holes I filled. Its always humid here in NC, but when the humidity get really bad, as in the last few days, the seepage happens at a faster rate. I beleive this is due to the wet wood in the transom swelling and pushing fluid out.

I thought it was the G3 transom corrosion issue, but from the wood Ive seen underneath when drilling, it doesnt appear to be treated, and the issue is only isolated to these spots, which happen to be near or below the bolts. What I'm thinking of doing is taking a cutting wheel and cutting out the areas surrounding the corrosion, hopefully finding dry wood underneath somewhere, and removing the wet wood, fitting a new piece of wood in, and having a new patch of aluminum welded over. It would be 2 sections about 10" apart from eachother.

Does anyone see any issue with trying this before having to replace the whole transom? I can get pics up a little later to help explain what I am talking about.

 

[bobberboy]

I don't know if answers your question. Maybe only in part. Several years ago someone on this forum was either making or repairing his transom. He was trying to deal with the issue of thru-bolts for the motor mounts and took a clever approach. In order to insure that he didn't have any issues with rot developing around the holes he over drilled them with a hole saw and filled the cavity with resin. Once in position he then drilled the motor mount holes through the enlarged resin filled holes and didn't have to worry too much about moisture migrating into the transom via the bolt holes. Care needs to be taken of course to keep moisture out but the resin filled holes protected the transom at the bolt holes.

I don't see why what you are proposing to do wouldn't work. Drilling out a couple of holes shouldn't compromise the strength of the transom. You can't know the extent of the rot until you get in there but if it is localized to the holes you described it seems that it would be ok. I wasn't sure whether you would be drilling from outside or inside but if using a hole saw to remove the rotted wood the pilot bit will go through the hull if drilled from the inside leaving 1/4" holes. If drilling from the inside you could start drilling with the hole saw until you are about 1/2" into the wood. Once the hole saw is seated in the wood you could remove the pilot bit and continue drilling without it. You can keep checking to be sure you're not drilling into the aluminum but also should be able to tell when you've made contact with it by the change in sound the hole saw makes. You can cut plugs out of material the same thickness as your transom with the same size hole saw and use whatever appropriate glue you want to replace the plug.

The one thing I don't know about is how much heat is generated when welding the aluminum patch on the outside. I think if it was steel, enough heat would be generated to start the wood smoldering but I don't know anything about aluminum welding.

 

[earl60446]

Does not sound like a good idea to me. If the wood is wet and rotten, replace it, the whole thing. No way resin shot into a hole will be as structurally strong as new protected wood.
Tim

 

[AMG08]

Thanks for the ideas so far. Replacing the wood isnt as easy as it sounds being that its on a 1860 and the wood is completely welded in. Im trying to avoid that at the moment.

 

[AMG08]

Here's a pic to show location. There are 3 spots. First is far left on the corner. I plan to just have that re-welded, as from what I can tell there's not actually wood underneath that part. Next is just above the bottom white spot (bolt head I sealed). I have it covered with jb weld for now. Next is just below the white spot on the right.

Im thinking I can repair the right and left holes easy enough by doing the hole saw method on the right and having a welded fix the left spot. The middle spot will present an issue though. I kind of want to cut out the area around there up to about a 1/2" from the weld and above and below both bolts, remove the wood, and replace everything with a patch of 5052 over top of it all. Does anyone know if there are nuts or receptacles on the back side of the left bolts? I cant get back there due to my rear deck.

 

[kofkorn]

bobberboy » Yesterday, 10:21[/url]"]... he over drilled them with a hole saw and filled the cavity with resin. Once in position he then drilled the motor mount holes through the enlarged resin filled holes and didn't have to worry too much about moisture migrating into the transom via the bolt holes.

I think this could be a good method for some of the non-critical components, such as sounder sensors and other smaller things. I would be VERY concerned about using this method on the bolts for the motor. At this point, you've completely separated the bolts from the strength of the transom. A few good bounces down the road, and the resin separates from the rest of the transom wood. Now when you go to do that hole shot, your motor decides to go for a nice swim.

On top of that, welding a patch over the wood (or even worse, resin) isn't a good idea. You are sure to scorch the wood around your weld area, and potentially start a nice smolder that would be impossible to extinguish. Resin will burn nicely once it's up to temperature. I wouldn't chance it.

It's unfortunate, but if you are really concerned, it's time to do it right.

Good luck!

 

[turbotodd]

if the wood is still hard (not getting soft) sometimes use of ethylene glycol (antifreeeze) will kill the rot. I've known some guys who've soaked the wood with antifreeze and then stuck a hair dryer in the bottom of the hull, facing the transom wood, to dry it back out. It's just temporary-but should get a few more years out of it.

If the wood is soft, replace it. If the bolt holes were leaking, you don't really know the extent of any rot until you completely remove the wood. If one was to use a hole saw and you sawed a 2" hole, and found rot was beyond the 2 inches, then you're back to square one anyway.

The transom is the most important part of any boat, IMO, and it needs to be in tip-top shape. I have seen guys run them "soft" and last a while (I did on a 'glass boat up to about 60 mph-which was stupid), and I've also seen the motor literally fall off with nothing to keep it from going to the bottom but the steering/throttle/battery cables and fuel line. And I've see a motor come into the boat before-and that was a pretty scary deal to see it happen.

 

[bobberboy]

.
Like all things you'd need to use some common sense. If you drilled holes larger than the inside washers and through the aluminum, and if your motor had no interior bracket then yes, your motor would go swimming. In your case you're talking about smallish holes that have nothing to do with the motor. As others have already said, knowing the extent of the rot is critical. If you have metal on both sides and the top is also encased I don't know how'll figure that out. I wouldn't drill any hole-saw sized holes into the aluminum for any reason.

So if your transom looks like this
.


maybe you'll want to do this
.

 

[acabtp]

if the corrosion has produced through holes to the exterior side of the transom, the interior side of the transom skin is much worse than you'd imagine (think swiss cheese). you have to pull it apart and get the old wood out of there... it doesn't have to be rotten, it just has to hold water to corrode your boat.

i'd expect that your repair is going to be more involved than just replacing some rotten wood though, unfortunately. post up some pics of the inside of that transom once you get it apart.

 

[surfman]

Here is what mine looked like on the outside then the inside.
Hole showed up, notice the weeping;



Took it apart, pretty corroded underneath, PT wood was used, it was the old stuff so it is not as bad as the new stuff but still will cause corrosion.





The wood;


Inside skin;


A 20 year old hull, get the picture…..


How I fixed it, https://www.tinboats.net/forum/viewtopic.php?f=3&t=23064