1974 MONTAUK: Brown Stains Seeping Out of Deck

[nlbounds]

I am in the process of completing my first restoration with a 1974 Montauk. I recently completed the exterior restoration.

I flipped the [MONTAUK boat] back [to normal orientation from being upside down]. I put the hull on the trailer.

I am now in process of restoring the interior. I started by sanding down the walls of the interior and then applying the Total Boat Total Protect primer to work as a barrier coat before applying the topcoat.

On June 11, 2020 I noticed brown liquid began to seep up from the deck where there was crazing, and [the brown liquid] stained the non-skid. I am assuming that once I applied the barrier coat to the walls this stopped the boat from being able to breath and caused the moisture in the deck to rise through the deck.

Fig. 1. Deck with stain area

deck1a.jpg (26.46 KiB) Viewed 1739 times

Fig. 2. Hole in deck fromobattery box

deck2a.jpg (15.83 KiB) Viewed 1739 times

After a few days of opening these holes and letting them dry out, I noticed in a few of holes I could see standing water.

It is important to note there are no soft spots on the deck or areas where the fiberglass feels loose.

There are spots when tapping with rubber mallet that do sound hollow.

Q1: What is this brown liquid that is coming up from the deck?

Q2: Should I apply the barrier coat over the entire interior to ensure all exit and entry points are sealed?

Q3: Should I build in deck vents using a garboard drain to allow the hull to dry out on days when I know it won’t rain?

Any help and suggestions would be great.

[jimh]

...I flipped the [MONTAUK boat] back [to normal orientation from being upside down]. I put the hull on the trailer....on June 11, 2020 I noticed brown liquid began to seep up from the deck where there was crazing and stained the non-skid. I am assuming that once I applied the barrier coat to the walls this stopped the boat from being able to breath, and caused the moisture in the deck to rise through the deck.

I don't think your assessment of the cause of the appearance of the brown moisture is correct.

To me, the appearance of the brown liquid seeping out of the deck is not related to any notion of the hull surface needed to be able to breath, which I presume you mean to say need to continually exposed to open air in order to be able to allow water to evaporate from the deck on a continual, 24-hour-a-day basis.

To me, the more likely cause is related to the boat having been stored upside down for a long period of time, then being returned to the normal orientation. When the boat was stored upside down, some liquids in the interior of the boat migrated to the lowest areas. When the boat was turned back to normal orientation, those liquids flowed again by gravity to a new lower location.

Q1: What is this brown liquid that is coming up from the deck?

In 2020 to have a brown liquid seep out of a Boston Whaler Unibond hull made in 46-years earlier is not particularly unusual or surprising. My best guess about the nature of the brown liquid: the brown liquid is a mixture of water trapped in the interior of the sealed double bottom of the Unibond hull, mixed with some uncured polyester resin from the original fabrication of the hull 46-years earlier.

I have seen brown liquid seeping out of screw fastener hole in the interior side of the Unibond hull of another Boston Whaler, a newer c.1988 boat. This boat was in immaculate condition. But one day some brown liquid began to spontaneously seep out of a screw fastener hole holding a rod holder on the inwale of the boat. It was quite a surprise to the owner, who had lavished great care on this boat since buying it new.

[jimh]

I am now in process of restoring the interior. I started by sanding down the walls of the interior and then applying the Total Boat Total Protect primer to work as a barrier coat before applying the topcoat

I don't think Total Boat Total Protect barrier coat was the best choice for a paint primer for the interior. That product is described by its manufacturer as being intended for use as follows:

TotalBoat TotalProtect is a heavy-duty, epoxy-based barrier coat and primer preferred by professionals to prevent water intrusion from creating blisters in gelcoat [and] fiberglass.

It sounds more like something you would use as a barrier coat primer before applying anti-fouling paint to a hull bottom

On the other hand, I really know nothing about re-painting a boat with Total Boat products. Perhaps you should consult with them for advice on your use of the product in the cockpit instead of on the hull bottom.

[biggiefl]

You were correct Jim. Barrier coat is not a primer in the conventional form. It is used on the bare fiberglass on the bottom before applying bottom paint to help deter osmotic blisters forming in the gel coat. I highly doubt it will have any value on the inside of a hull unless you plan to leave it submerged for VERY long periods of time.