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Foam or other product to fill void that won't absorb water.

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Foam or other product to fill void that won't absorb water.

Old 06-09-2019, 09:14 AM
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Default Foam or other product to fill void that won't absorb water.

I was helping a buddy get his boat cleaned up and he has an area under the bow that I found that had water in it. The boat is a 70's vintage Grady White that he bought new, he is 92 years old and still uses the boat. We use mine mostly but we will go out on his boat several times a year. He didn't know the area had water in it so who knows how long it's been in there. The only way to get to the area is to run a hose about 6' under the floor and try to pump the water out because there is no place for the water to get out. The boat is rough but he has no plans to get another one or do any kind of major work done on it so my only possible solution was to possible inject something like foam that will expand and fill the area but is there a foam that will not absorb water?

The bow deck is soft so there could be numerous places the water could be coming through, I went to stand on the deck and immediately knew that I would likely go right through. I'm asking a specific question about any suggestions to fill the void, he isn't going to fix the cause of the water getting in so I don't want a bunch of information about fixing the cause of the water getting in. The guy will be turning 93 at the end of the month and he knows the boat is going to be junked when he dies. I think he is on his 4th motor so I couldn't even guess how many hours are on the boat.

Is there a foam or some kind of expanding product that won't absorb water? If I can do something that will just reduce the water it's holding by half I want to do it.
Old 06-09-2019, 09:53 AM
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Pourable 2-part urethane foam, 2 lb density, avail any marine store or online, you'll need an access port at the top and be careful not to put in too much as it could blow through the weak deck as it expands
Old 06-09-2019, 09:59 AM
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Chaps is correct on the material.

The only issue is whether he should use a 4# instead for the structural strength over the 2#. If you just want to fill the space with no need for any support then 2# will work, if there is a need for some support due to a soft deck using the 4# can have benefits.

In either case, the foam is referred to as closed-cell, so it will not absorb water.
Old 06-09-2019, 12:15 PM
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What they said^^^^^^^
Old 06-09-2019, 06:29 PM
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What happens if the area is exposed to water for a long period of time, like months? I thought even with closed cell foam that it would eventually absorb water so if it doesn't than that is news to me. The only access is under the bow deck and the area runs for about 6', I am going to have to try to think of a way to pump the foam mixture as far back as possible. What I don't want to do is to create a dam where water could actually accumulate in front of the foam.

What do you guys think of possibly running a piece of PVC conduit and then pour the foam over it? That way if any water does accumulate on front of the foam at least it will have somewhere to go. It's actually pretty piss pour design to have an area like this that has no where for water to go. My Scarab Sport had a large hatch in front of the console and water accumulated under the hatch and the same piss poor design because there was no way the water could get out of the area. I ended up drilling holes in the bulkhead to allow water to flow into the bilge. Shocking that 2 boat builders could make this same mistake.
Old 06-10-2019, 06:32 AM
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I think 2 part foam will do the job, but I can't think of anyway you can pump it anywhere. It mixes 50/50 and you then have less than a minute to pour it where you want it.
From what you describe it seems like cutting the deck would be the only practical way to pour it where it is needed.

When I used it I prepped wax paper or plastic bags, thin plywood and a way to wedge the plywood in place. I poured the foam, laid the plastic over the void and then secured the plywood over that. It forced the foam to expand where I wanted it and not straight up. Also resulted in better density I think.
Old 06-10-2019, 06:40 AM
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Some pictures of the area may help, if you feel like it.
Old 06-10-2019, 06:48 AM
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You will need to cut access for a pie plate.

​​​​​​​stuff kicks really fast

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