How eff'ed am I? Transom rot

[FishyDownThere]

Hello!

I recently bought a small aluminum boat for fishing. On my first trip to the lake, I noticed water seeping into the boat. The transom is made of single-skinned aluminum on the outside (the hull), with exposed plywood on the inside. It appears that the bilge pumps were not working properly, allowing water to reach the wooden transom. After draining the bilge water, I noticed signs of deterioration and potential rot in the plywood transom.My plan is to strip the boat down to bare aluminum, fill it with water to locate and mark any leaks, and then have them repaired. However, replacing the transom plywood seems daunting due to the boat's welded splashwell and welded platforms for rod holders. Would thoroughly drying the transom wood and applying a coating of epoxy be sufficient for repair?
 Thank you in advance for any help!
 

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[gandrfab]

With or without pump or pumps that wood was going to rot.
I'd replace the wood with aluminum box tube.
Cutting the transom cap and or splash well as needed then welding it back together.

All depending on the condition of the rest of the aluminum.
 

[FishyDownThere]

Thank you for the reply. The hull is from '91 and could still be using the original wood transom.

Does your recommended method with the aluminum box tube look something like this?
 

I did some basic tests with the outboard (50hp) before buying:
1. With motor fully raised, I tried pulling down on the motor to check for any flex, but didn't notice any.
2. I lowered the motor and performed a shake test on the lower unit, again observing no movement in the transom.
Are there any additional tests I should consider to assess the condition of the transom?

After reading online, it seems that drilling into the transom to inspect the shavings for moisture content is the best way to test for wood rot. Would it be advisable to try this method? I suspect that the outer edges of the plywood and the bottom may have the most damage. Is there a general rule of thumb for determining when to replace a transom? For example, if there's any chance of rot, should it be replaced, or perhaps if 20% of the ply is affected by rot?

I apologize if these questions seem basic; I'm still learning about boats!

 
 

[kmorin]

Fishy', welcome to the AAB.com Forum.

If you've read here or on 'tinny' sites ? you've heard that wood against aluminum- closely fit-up joints that are allowed to have standing water in between the two materials; usually results in the water becoming acidic and pitting the aluminum.  

SO, if you're looking for a long term cure/ boat restoration? That's pretty involved and implies taking the wood out and repairing the transom before A) replacing a new wood panel with proper prep, or B) building a new transom assembly or all aluminum; then re-attach to the hull via welding or riveting??

Both are plenty of work to try to justify for this class (inexpensive) skiff.  The pitting can be localized and  therefore 'repairable' by one means or another or; Global... spread entirely around the metal transom to wood contact surface - and just getting to that stage of real knowledge is plenty of work.

If the ply is de-laminating already, as shown in photo under panel's edge from the bilge.... then the strength of that panel is beginning to go away.  On the other hand if you've pulled on the leg and  not seen flexure?  Maybe you can still use the skiff until its time is 'up'?  Calk the leaks and go, work to make your bilge pump reliable and keep an eye on the bilge water and use her as much as you can?

Other views, depending on the hours of work other owners are willing to invest, might range from - "take it to the dump" to " strip it clean, etch the hull and begin to rehab the damage done."  I see it as a question of what you'll have when you've done any given course of action vs what you'd use that time to do otherwise?

No need to apologize about asking questions, that's why Welder put the site up to help others learn about aluminum boats.

Good luck with your project & Welcome to the Forum.

Cheers,
Kevin Morin
Kenai, AK 
 

[gandrfab]

 The jon boat or 'tinny' transoms I have rebuilt.
Removed all the wood and used square box tube the same thickness the wood was. Normally keeping the old stringers and gussets intact and tying into them.  
One cross tube the width of the transom at the top of the transom. Normally under the transom cap.
2 vertical box tubes that will line up with the motor mount holes and or a 2nd cross tube in-between the 2 vertical tubes.
Clamping and plug welding the old transom to the new tube.
Somehow tying the new vertical tubes into the existing stringers and gussets.

Googling "jon boat aluminum transom rebuild" finds a bunch of. I wouldn't go that route, keeping or replacing with wood and/or constructing hard point gussets to the hull bottom or rear seat.

Once the cap is out of the way somethin like these may be good start.
Not my work, found these on the WWW.

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[FishyDownThere]

Maybe you can still use the skiff until its time is 'up'? Calk the leaks and go, work to make your bilge pump reliable and keep an eye on the bilge water and use her as much as you can?
 

Copy that, fish it 'til the wheels fall off!    
 
Thank you both for the guidance and ideas. I will address the bilge pump situation ASAP and ensure that I have a few backups on hand. I'll keep a close eye on the condition of the transom and will plan to replace it as per your recommendations when the fishing slows down.

Cheers!

[gandrfab]

If your going to drag it out maybe look into a rot stop product.
https://www.google.com/search?q=marine+ ... e&ie=UTF-8

And add larger washers or plates where bolts go through wood.