Mariner 420 2004 - water in swim platform

[bud37]

A lot of times it is just simply water getting in to the coring through screw holes. These platforms have a rub rail around the perimeter with caulking and fasteners........check all those spots near where the moisture meter numbers are the highest as balsa cores will wick up moisture as it travels away from where it gets in....anywhere there are fasteners of any kind or any damage, look for gelcoat spider cracks working away from the edge from a docking impact......good luck in your search...

Edit.......is your platform open from inside the boats engine room, check there for where you can visually inspect for leaks....if you have those round inspection fittings on the under side, check the rubber "O" ring to see if they are sealing properly.

[Viper]

Anything that penetrates the platform or adjoining structure can be a source for moisture getting into the platform, I see a hinge on a platform hatch for example. Also look at the swim platform ladder, inspection ports, dinghy davits, BBQ mounts, etc. I'd also open the transom lockers and see if there are possible sources for water intrusion into the platform. Certainly the mating edge between the hull and superstructure that's covered by molding is always suspect. The platform wings/splash guards on both sides of the hull are also a common source for water getting into the platform substrate if they're not sealed properly. The scuppers of course is suspect as well. The fasteners, the bedding, and how the draining water is directed there can be the cause too. It also looks like you have access ports under the platform, and while they might be letting water in, it's unlikely they're the source of the top core getting wet since this is a hollow platform, still it's something you should ensure is properly sealed whether they are inspection ports or not. BTW, if the body of the scupper is still in great shape, you can buy just the rubber flap separately. They tend to relax over time especially when they're mounted under a platform.

It's going to be a pricey fix but it'll be pricier if you let it go for too long.

Where is she located?

[Lruel]

Anyone has more insights?

Thanks again formthe help


Laurent

[Lruel]

Anyone with new insights or suggestions?

Thanks in advance

Laurent

[Lruel]

So, after opening the platform, it is clear there are 2 places where, by design, the water goes into the hollo platform. 1 via the hole where the electric cable passes and a second hole where the electric cable is rolled in.

I asked the fiber guy to put some openings that I will unscrew to let the water go out before winterizing, so that if there is still water in the hollow platform it will not freeze and crack the fiber.

[km1125]

I can understand a few reasons why they might want to flood a compartment like that, but it seems crazy that they wouldn't make it self-draining. It's not the first time they built a boat. Post up some more pics and maybe a diagram. I don't know of a 420 around me or I'd go look at one because I am curious what you're running into.