# Rebuilding jon boat transom (wood), have a couple questions



## TDIdiver26 (May 10, 2019)

My current boat is a aluminum 1648 MonArk riveted jon with an 8hp Mercury 2-stroke on it, which weighs roughly 80 pounds or so - not sure, it’s light enough for me to easily remove and replace it to put it on a stand. I’ve never had an issue with the transom on my boat until it filled up with water during Hurricane Irma and sat like that for a full day before I was able to get it drained (on the trailer, just too much debris near the drain hole and it got clogged up). Now the inner transom board is beyond soft on the entire left side of it and it needs to be replaced.

My stern has a 3\4” thick board on the outside of it (which ironically enough is still 100% solid) and what I assume is two 12” wide x 3/4” thick pieces of wood sealed together as the inner transom.

If I get marine-grade plywood, I was planning on buying a 3/4” sheet from InnerCity Lumber in Tampa and cutting all three replacement pieces from the one 4x8 sheet before drilling the bolt holes and epoxying all three pieces before installing them and replacing the bolts, washers, and lock nuts (all sealed with 5200).

Since I plan on epoxying it (fully intending for this to be a week or two long project because my motor is due for service and I’m sure at this time of year that will be at least 7-10 days before getting it back, which is fine) regardless, should I use the marine grade wood or will regular plywood suffice? The weight is a concern for me as the stern sits pretty low unless I have a passenger on the bow (I’m rather big at 275-280 pounds), which is why part of the renovations I plan for the boat include adding a grab bar directly behind the second bench seat to allow me to drive the boat from a couple feet forward of the rear seat. It will still run pretty quick with myself and one other person in it but I may repower it in the future if I can find a good deal on a 15-25hp tiller.

I’ve included a few photos of the stern so what I’m talking about is a little more clear (the boat has been sitting at my parents’ house for a while and needs to be pressure washed but I’m going to wait until I get all the old transom wood and wiring out of it first so I have a fresh surface to work with.


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## Smackdaddy53 (Dec 31, 2012)

Regular BC ply is fine if you are sealing it but if you have the money go with marine ply.


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## No Bait / Lures Only (Apr 10, 2011)

I had a very similar monark 1852, good boat but popped rivets on transom knees at da bottom. Also welds cracked on transom to side corner braces. 2 pieces of epoxied 3/4" plywood should be adequate, fabricate plywood larger, all d way to bottom. Factory didn't do that n was a defect when running larger engines. Mine was rated for 50 hp 1972. When I ordered my boat, had 2 transom knees n it helped some. Bottom flexed when running while porpoising n caused the problem.


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## DuckNut (Apr 3, 2009)

Your plan is very sound. Get er done


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## Howard Cummings (Apr 8, 2016)

How do you remove the wood from inside with out taking off the transom cap


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## DuckNut (Apr 3, 2009)

Howard Cummings said:


> How do you remove the wood from inside with out taking off the transom cap


Look at his pictures...self explanatory.


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## TDIdiver26 (May 10, 2019)

The interior transom boards are only about 12-14 inches wide so unless I’m wrong they should slide down and come out without having to remove anything... if nothing else the one side is soft enough I could just break them in half (or 60/40) at this point, it’s putting the new wood in that would cause an issue LOL.


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## DuckNut (Apr 3, 2009)

Nope.

The wood colored ones in your pic look to be the ones you are referring too. You need to replace the gray ones as well. 

The light colored ones don't look to be an integral part of the gray ones, but it could be the pics.


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## TDIdiver26 (May 10, 2019)

DuckNut said:


> Nope.
> 
> The wood colored ones in your pic look to be the ones you are referring too. You need to replace the gray ones as well.
> 
> The light colored ones don't look to be an integral part of the gray ones, but it could be the pics.


The gray wooden transom boards are the ones I’m referring to in regards to replacement. The tan/wood colored center piece is an aluminum plate. There’s another bluish-gray board on the outside of the hull as well (no idea why it was done that way, but it’s held up fine and it doesn’t have any damage as I said in the OP, but since I’m paying for the cost of a sheet of plywood either way I might as well replace all of it at once I guess.

Unless I’m missing what you’re pointing out, that is... 

Also, on the exterior board: is 5200 sealant enough to stick it to the hull (plus the existing bolts), or should I use some other kind of adhesive as well over the entire surface area after the board is epoxied? I don’t want water getting between the wood and aluminum.

Again, total newb to this as I’ve never done it, so if I’m asking stupid questions then forgive me. LOL


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## lemaymiami (Feb 9, 2007)

Simply fiberglass both sides of the wood before mounting it back into place (and as noted extend the wood out to cover a bit more of the transom than it does now...). Properly glassed (single layer of fabric with resin on the bare wood first then resin covering the glass so that it's all sealed up.. and allowed to cure out before setting into place on that transom. That's why you don't really need marine ply -simple BC plywood will suffice if you're going to glass it. Using just bare wood, then you do need marine grade plywood since it has much better glue holding the plies together (and no voids....). Yes, you can also use 5200 - but only around the edges since otherwise you'll never be able to remove it if a repair is needed in the future... and if that wood is glassed it' s pretty much waterproof...

Aren't boats fun?


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## DuckNut (Apr 3, 2009)

My guess is that the wood on the inside is deteriorating and flexing, that is why somoeone put some on the outside.

Make a template of the size you need and do as Bob (the post above this) said to do except use two pieces (min 1" thick). Then use the epoxy to glue the two pieces together. Then once that is all bonded together and sealed on every inch then put it in place and use bolts to hold it to the transom. You can use 4200 to coat the bolt and bolt hole when mounting.

Since this is a tinny and the job is so simple do not overthink it. If you just slapped the plywood in there you would probably get 7 years or so. This is not a case where it will cost thousands to redo it in a decade so just get the job done and go fishing.

You should be able to be done by Saturday night.


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