Cracked transom aluminum

[chadzeilenga]

Hi All,
I pulled the transom pad off to replace and discovered a problem underneath

The screw in the center of the transom appears to have partially pulled through. The transom wood is still in good shape, so I’d like to avoid replacing at this time.

Has anyone seen this and have any recommended repairs? I was thinking of using a stainless thru bolt with large washer and some 3M 5200 to seal and provide barrier between AL and Stainless.

I’m still trying to find a transom pad solution as well. I’m concerned rubber will dry rot over time


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[DaleH]

I'd advise that before you do anything, I'd assess "why or what force" was causing that screw to pull through. Where is it attached on the other side? To me it means whatever it was attached to on the other side was being moved forward, hence the 'pull divot'.

And I would never attach anything or goop it (3M 5200) without priming the tin first and yes, isolate the tin from anything stainless.

 

[chadzeilenga]

Hi Dale,
Thanks for the response and I agree, I need to diagnose what caused the issue to prevent from recurring. This bolt is in the center location of the transom, so I would imagine that it sees the most force when there is any load on the transom. The head of screw is just a tapered philips screw, so there was no distribution of the loads to the area around the screw head as with a washer. It was still tight when I removed it and the transom aluminum appears to be pretty oxidized so I don't think there has been any movement recently, possibly it was an older failure?

I'm trying to find a better solution for a transom pad that will more evenly distribute the load of the motor to the transom, but I can't find much discussion on the topic. Has anyone used the pads made by NuovaRade. I was thinking of installing one on the outside:

https://www.nuovarade.com/product.php?productId=5527&categoryId=141

And this on the inside:
https://www.nuovarade.com/product.php?productId=5525&categoryId=141

With 3M 4200 sealant around all of the bolt holes which would be thru-bolted.

 

[DaleH]

A suitable sized HDPE cutting board sized to fit would work slick on the outside and is a much cheaper option ...but I am admittedly a DIY'r and try to do things myself, vs. buying pricey specific-use parts.

I also use what you showed on the inside, more so to absorb or minimize any OB vibrations.

 

[Weldorthemagnificent]

I use 1/4" aluminum plate. I've welded it into one piece, or simply put a piece on each side. Really helps spread out the forces from the motor. Also either use a transom saver or ratchet straps the motor forward while trailering. The bouncing will take its toll.

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[chadzeilenga]

Interesting, I could probably get some AL from McMaster. What grade do you use?

 

[Weldorthemagnificent]

It doesn't matter because it's not hull material. Shop I work for happened to have some drop 5052. 3000 series would be fine as well. Check local fab shops first it would likely be a lot cheaper if you could find a piece

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[UP BOATER]

As far as that little pucker goes I have had good luck with JB Weld, yeah and agree with Weldor on the plate. I use whatever Aluminum plate I have laying around, here is one I did recently, this one is 1/8”

 

[chadzeilenga]

Thanks,
I think I'm going to get a 1/4" Aluminum plate for both sides of the transom and then through-bolt it with some 316SS hardware and isolate the hardware from the AL with either 3M 4200 or some rubber washers. I'll put the 3M 4200 on the backside of the plate as well. I'm not yet sure how much this will increase the vibration over the current setup, but should help by adding rigidity to the transom. It's been fun wading through the McMaster-Carr bolt selection online as I found some nice AL screws to seal up holes with as well.

 

[DaleH]

... then through-bolt it with some 316 SS hardware ...

Be aware most local stores will only have 304 series or 18-8 stainless hardware. On my saltwater boats I buy 316L series as it is passivated and high in molybdenum content to better withstand the salt environment. The 316 also doesn't "bleed rust" stains like the cheaper SS series will.

I buy mine from Albany County Fasteners: https://www.albanycountyfasteners.com/screws-bolts/acf_cat_screws_and_bolts.htm?Per_Page=144&Sort_By=bestsellers&f_material=316%20Stainless%20Steel

 

[chadzeilenga]

Hey Dale,
thanks for the resource! I will definitely check them out. I've been navigating through the listings on McMaster and have a set of 316SS hardware selected. Since I won't be doing any salt water, this was just added insurance for cosmetics with the bleeding like you mentioned.

After some further reading, I'm a little concerned with my 1/4" AL plan and the motor sliding around on it.

 

[nccatfisher]

It won't be anymore apt to slide on it than it did on the original transom.

 

[chadzeilenga]

It won't be anymore apt to slide on it than it did on the original transom.

Good point...


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[chadzeilenga]

Well I finally got the new AL plates installed

I have some cleanup of the 3M 4200, but it went very well. I used 316SS hardware with a barrier of 4200 on it.

Also, I had some holes in the transom from an old depth finder. Plugged them with some Aluminum screws

I appreciate all of the input from the team here! Can’t wait to take it out. A few questions:
1. What do you hook the motor chain to?
2. What is best way to remove the 4200?


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