Since we're talking boats, been meaning to ask this here for a while.

Last couple times I used the boat (2000 17' Bell, fiberglass hull, made in POC, lives in Flour Bluif), I've noticed that after rinsing thoroughly in the driveway, letting it dry a bit and then putting it into the garage, the hull "sweats."

There will be a small puddle of saltwater on the garage floor under the lowest point of the hull.

I don't have any scrapes, gouges, etc. on the hull.

What causes this and is it a big deal?

Condensation due to warm fiberglass, cool garage, and still/humid Flour Bluff air?

This sounds like the fiberglass isn't sealed well and it's damp/wet.

That thought came to mind. But it just started happening in the recent past, didn't have the issue for years.

Never heard of that. Can you get under and try to see exactly where it's coming from? Sure it's not dripping out of the bunk carpet? It can take a long time to dry out.

Anchor locker with a drain? Hatches drains?

Check the hull lines. It is running down the outside of the hull down the lowest point then dripping. Could be coming from anything screwed into the outside of the hull (like trim tabs, transducer, even the bow eye). Wash it....then let it "dry". Then get a tissue or paper towel and see which screw is leaking.....which then runs down the hull to the lowest point and drips.

When you say the hull "sweats" are you talking about the entire hull ( which is everything below the rub rail) getting condensation on it?
Or is the hull dry and you are seeing water at just one spot?

I am asking this for a reason. I have seen hulls "sweat". It wasn't really the entire hull but was where the foam flotation was in the hull……which is typically under the floor or up the hull sides a bit…..so the bottom or running surface and up the hull sides can sweat…..here's why:
Some manufacturers used to cut cost by using flotation foam that is not closed cell flotation. Non closed cell flotation can absorb and saturate with water faster than closed cell foam if water can get to it. Once flotation foam gets saturated it's almost impossible for it to dry out.
The moisture in the foam will try to evaporate which causes a temperature gradient which can cause the outside of the hull to "sweat" or condensate.
Another symptom of the foam being saturated with water is you can notice your boat not performing as it used to as it's heavier due to the water in the foam…..however, this will occur only when the flotation foam is heavily saturated.

It should be absolutely impermissible to use non-closed cell foam in any boating application. It has no business being a component of a boat hull. In no way is it ever worth the minor cost savings. USCG 2 part closed cell foam only. That's what I used I my boat bulld and 20 years later it is performing great.

I'd suspect a leak in a through hull fitting or something drilled into the sole. Water is getting inside and the slowly leaking back out.

Good to know. There's an entire regimen of good materials, proper sealing, and proper maintenance required to keep a boat hull in good working order. Glad to see some people are aware of it.

From reading your past post over the yearsI know you are very knowledgeable in boat building. ….and always enjoy talking with you.
In the last few years there has been some real advancements made in the chemical characteristics of polyurethane and polyethylene foams…….making them not only better for flotation but also for tremendous strength and rigidity applications as well. Basically allowing boat builders the advantage that now the flotation foams can also add great strength and rigidity to their hulls ……without weighing as much as the standard old polyurethane flotation foams did.

On a side note perhaps we can meet up someday as I would love to talk boats with you!

Sounds like a good time. Boat design and construction has always been an interest of mine, plus also fishing from them. Yep, with modern materials science they can make some superb boats. And the engines are crazy.

The outdoors board hasn't had a fishing meetup in a long time. Maybe it's time to change that.

Thank you for all of the replies.

CS78, that is a possibility. I may have slightly lowered the tongue jack a while back which could result in the bunk carpet being the culprit.

Grem, all good points which I'll explore further.

Gunny, thanks for the info. Next time I'm in the Bluff for a fishing weekend I'll get the moisture location nailed down better. But it's definitely below the chines where I noticed it, and ultimate slow dripping from the keel. I have made it a point to notice any possible sluggishness while out on the water since first noticing this, but the boat seems to get up on plane and perform as it always has.

Definitely all good points so that I can take a deeper dive next trip down that way.