Beneteau 49 Bow Thruster Battery Shelf

[CaptainSV-SecondStar]

Greetings all,
I had noticed this before and on checking it out again recently I've decided to remove and replace the mount for my bow thruster battery. As you can see from the image, there was some previous leakage and battery acid damage to the laminated plywood (marine plywood??) shelf, at each of the four battery box screw holes, predominantly in the port, aft area (the image is looking forward). One of the plastic battery strap 'hold-downs' has also failed. Easy removal of the board, and it is not too big - 9.5" x 35.5" x 1" thick.

I'm writing to ask for recommendations for replacement board/material for this shelf. I'm leaning towards StarBoard (likely same thickness to get the rigidity needed) rather than a marine plywood or solid hardwood but would love anyone's experience and thoughts on this. And if wood, how did you prep the wood for use - varnish? polyurethane? etc.

Thanks in advance!
Brian.

 

[Gunni]

There should be no leakage. There should be no holes in the battery box bottom. The battery box must be secured with straps, or braces that are outside the battery box. Cleanup what you have and install the battery properly. Starboard does not have the strength of plywood in this application.

 

[CaptainSV-SecondStar]

Thanks Gunni. Any recommendations based on experience on the best type of plywood and how you would treat the surfaces/edges prior to install?

 

[DougM]

As long as its inside the boat, I would think that a piece of cabinet grade plywood. (It is usually available at Lowes or Home Depot in small squares, so you would not need to buy a whole sheet.) would suffice with several coats of polyurethane on it. Also find a proper battery box with no holes in the bottom. You should never have a had a leakage problem in the first place.

 

[Gunni]

It does not look like a location that is visible so I would clean it up, neutralize the acid with baking soda, dry it, sand it up and epoxy the entire thing. Finish with an white enamel paint to match the surrounding. Epoxy is a great way to turn plywood into a strong, sealed material. Keep it simple.

 

[seadaddler]

Maybe leaking from heeling and get plastic battery box and check
how charging and not over charging.
Nick

 

[CaptainSV-SecondStar]

Thanks guys. And to be clear - I am not the original owner, and I suspect that this install is original, meaning that the dealer used wood screws covered with silicone through the bottom of the battery box into the wood shelf, in addition to using the tie-down strap. One of the tie down strap attachment points failed - though apparently more due to age/brittleness than contact with the battery leak. And yes, I get that a battery leak is not desired. At all. And the battery in there now is an AGM, charged through a Blue Sea Systems 7610 SI ACR and set to AGM on my controller. I am not sure if the damage to the shelf was caused by a different battery at a different time/owner. Back to the shelf: I will not reuse the existing shelf because delamination has already started. I am thinking marine grade plywood sealed with epoxy but not painted (this needs to be structurally sound but not pretty), and replacing the battery strap, perhaps with one that has a stronger hold-down point.

 

[Gunni]

Strictly speaking an AGM does not require a battery box BUT the bow is an extremely bouncy location you want the battery lashed down 9 ways to Sunday. Through-bolted tie downs and marine-ply would be the minimum. Dry fit, drill any holes, and coat the entire thing with a slow set epoxy to saturate. Install.

 

[CaptainSV-SecondStar]

Concur. Through-bolted tie-downs make a lot more sense than the original installation.