Rust From Embedded Metal in Deck

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
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Joined: Wed May 05, 2021 3:20 pm

Rust From Embedded Metal in Deck

Postby jps10 » Wed May 05, 2021 4:56 pm

Q1: Did Boston Whaler use a metal fastening component below the deck laminate of the 17-foot hulls made c.1987?


Hello CW. I'm a new to this forum but participated in the old forum.

I modified my [1987--always use four digits for years] SuperSport 17 hull to a [Center Console] between 2012 and 2014. At that time, I cleared the deck of all attachments from the previous owner and from Boston Whaler. With nearly every deck screw or other fastener and hardware removed I used West System epoxy to fair and seal the deck penetrations.

Due to more than 60 fastener hole repairs, the non-skid pattern looked pock-marked with 3/4-inch-diameter to 1-inch-diameter repairs, so I prepared the entire deck for AwlGrip finish with Griptex. I am satisfied with appearance, the performance, and the durability [of the refinished deck].

There is still a single fastener that I was not able to remove back then. As I recall, I likely just ground it to below the deck laminate and then filled and faired and on to the end objective.

That repair looked great, except over the last two years a rust stream has appeared over that filled divot. This boat is kept in the water year-round in southern California, and it is exposed to wet decks of humidity, wash downs, and rain. The decks drain and dry well enough, but the Griptex component for non-skid tends to hold moisture on the deck longer than the gelcoat non-skid did. But, otherwise, the entire deck drains dry after wash downs, rain, or morning dews, in a few hours. The bilge pump is always functional and vacates the sump down to the last one-inch of water.

Last week I decided to remedy the deck rust-bleed by removing the remains of the offending fastener by grinding around the perimeter to expose what I thought would be the remaining shank of a screw. I planned to use a VicGgrip plier to remove it. Then I was going to fill and fair; then be done.

After additional work with Dremel too past the laminate and into the 1/2-inch plywood, a bigger part of a fastener was reveled. I think the fastener is a large #12 or #14 screw, driven in at a angle, not vertical.

Since I did not want to make site opening bigger, I want to know about use of metal fastners or braces into the ply to connect to a bulkhead, beam brace, or other wooden deck support.

I've never heard of this before for in a Boston Whaler hull. I have never had reason to research it further than the "Wood Layout Diagram' for this model.

I've read here the 1/2-inch plywood decks were a "100% hull liner intergrated" construction product; supported only by the hull perimeter and the floatation foam, that is, contained no wood braces, supports, or bulkheads.

If [the source of this rust] is some type of original component, I'll live with that. Leaving it in and repairing over it is not a problem. But I'm sure in five years or less I'll see the rust bleed thru again.

This boat is not an show contender, but I do focus on keeping the hull sealed and dry to keep fishing and cruising it offshore at least nine months of the year.

At this point, presuming this metal remnant is not an original part fastener and should be eliminated entirely, I plan to use a hole saw and drill around the fastener. Once out, I'll plug the hole. Right now the object looks like remnant of a large screw by previous owner. The remnant still buried through the plywood and looks clean and unruste], which tells me the laminate-to plywod bond' is still a water seal. Noneth less, I've gone this far. I am resolved to remove it.

I just want to be certain metal remnant isn't a necessary originally installed deck component--and seriously doubt it is.

The general location is 15-inches forward of front of sump, 16-inches from l[Port] deck gutter[possibly where front face of rear mahogany bench seat may have located on this former Super Sport

Appreciate any relevant thoughts or advice. Thanks--Joe

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Re: 1987 SuperSport conversion: rust from deck fasteners question

Postby dtmackey » Thu May 06, 2021 11:29 am

When I did my restoration I ground down the non-skid and went with a Griptex and Awlgrip surface. I do not have problems with it holding water.

When I was grinding I did find a piece of iron metal cast into the fiberglass-to-gelcoat interface. It was small and an obvious defect from when the boat was built.

I know this is not what you are describing, but for your repair using a cut-out-and-fill methodl, I would also glass over the repair with glass cloth so the repair is bridged with the fiberglass to the surrounding deck, otherwise the repair area could separate over time showing the outline of the repair.


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Re: Rust From Embedded Metal in Deck

Postby jimh » Thu May 06, 2021 12:55 pm

It is well known that in molded early Unibond hulls, particularly in the 13-foot series, there were metal components embedded into the hull. Electrical flexible conduit of a small diameter was laid into the molds near the gunwales to act as a venting mechanism to help air evacuate. Some old 13-foot hulls sawed up have revealed the remains of this electrical conduit. I was told about this by Bob Dougherty himself, when I had lunch with him one afternoon at the Miami International Boat Show.

But the material you describe in the epic narrative saga above does not sound anything like a run of electrical conduit.

Also, I believe use of the metal flexible electrical conduit was not continued forever. I suspect at some point in the production epoch of Unibond hulls that technique was abandoned.

Information about the internal bracing used in making the initial Boston Whaler hulls is given in the patent granted to Richard Fisher. See the article in REFERNCE for a reproduction in HTML of the patent that I created.

Original Patent of the Boston Whaler Hull Construction