Hull/ Deck Joint on 380 Aft Cabin

[Rover4679]

Two weekends ago while making a trip across Mobile Bay, I heard what sounded like screws being pulled out of a plastic hole only to stop and find the hull to deck joint being pulled apart for most of the width of the swim platform. I did have a small dinghy and motor on davits on the platform so I immediately removed the motor and stowed the dinghy against the aft cabin for the rest of the trip.
After getting back to home port and removing the trim, I noticed that not only was the hull/ deck joint not sealed, most of the screws had pulled down and out due to there only being about 1/4" of overlap in the joint.
After further inspection, it seems that Sea Ray encapsulated a 1" piece of wood into the top of the hull to allow screws from the deck section to seat in. For whatever reason, someone at SR decided to cut the top off of this 1" section (you can see the saw cuts), not only reducing the intended mating surface but also leaving exposed wood to rot, which it did.
The rest of the Deck/Hull joints look ok but this was a very nasty situation for a few moments in the water as we were taking in water with every pitch.
Sea Ray states a weight limit of 400pds on the swim platform but I had less than 300, thankfully, or my transom may be history along with the boat.
Making plans to have the entire joint reworked to include removal of the rotten wooden piece and glass in the entire Deck/ Hull joint across the back.
Has anyone else ever had similar issues? Ever checked? I'll post pics if anyone is interested.

 

[Stee6043]

My first thought is that it's a bit presumptuous to assume the condition you observed originated at Sea Ray 23 years ago. Many things could have happened in that time, unless you're the original owner?

My second thought - you could hear a screw moving/grinding @ the transom/swim platform whilst at the helm of a 380AC underway? That had to be quite loud/significant? I'm imagining you're going to find a lot more rot in your transom if it was moving enough that you could notice it from the helm. I wouldn't expect that 1" piece of wood you referenced to be structural in any way...

 

[Rover4679]

Its obvious that it originated at SR as I doubt the deck was removed from the hull, holes filled in flawlessly and reassembled with screw holes only mating up 1/4" of joint "lip". Obviously it held for 23 years but it was not installed correctly when the sections were put together. I am the 4th owner but have has conversations with 3 or the previous owners. It seems I am more than likely the only one that travelled with the dinghy on the swim platform.
You are correct on the wood as it was intended to give the screws something to bed into. The problem is that it was never mated together fully, which allowed the screws to pull out. I'm sure there has been a lot of fatigue in this area over the years.
Yes, it was very loud as we were pitching and rolling significantly. The intent wasn't to "blame SR" although this was a QC issue, but more of an effort to give others something to look at while installing dinghy davits on swim platforms. Without the integrity of the deck joint, the transom has a lot more flex.

 

[Chris L]

Pics would be great if you can get some

 

[John E3]

Is this visible if you look up from inside the transom?

 

[Rover4679]

Pics coming this weekend. Yes, if you remove the kick plate next to the aft vanity, you can slide in and look above where the hose and wires run across the transom. You can see the joint and the end of the screws. Just notice how close to the edge of the joint they are. Aldo, stick your finger in the space above the hull portion of the joint to notice if the wood is exposed. If so, it is likely rotten.
Other than access, it's a relatively easy fix but a necessary one if you haul anything on your platform. Hopefully, mine was the only issue.

 

[John E3]

Looks like this, but shaved off the top? This is a series of short blocks. Could have split along the screwline?

 

[Rover4679]

Yep! The gap in your looks much better than mine. The top of those "blocks" on mine were cut off, exposing the wood inside. The screws protruded through the top of that area at about 1/4" or so. What's weird is the factory original Grey paint was coated on top.

Who knows, maybe they had a hard time lining mine up that day. I'll get pics this weekend. Thanks!

 

[Rover4679]

I looks like the enclosed wood section at the top of the hull was not really enclosed or encapsulated. Luckily, the glass around the wood is pretty thick so I ground it out with a wire wheel. I'll fill it with epoxy resin mixed with silica the glass the joint. The 2 screws in the pics were just put back in to hold things in the correct location. You can see their proximity to the edge of the "lip".

Hopefully, mine is the only one like this. Had I not put the dingy on the swim platform, it may have been just fine.

 

[Rover4679]

A few more pics

 

[Rover4679]

A few more pics