CONTINUOUSWAVE

Q1: what brand and type putty is used by Boston Whaler in their putty box?

I tried [asking] Boston Whaler, and my local [authorized] dealer to no avail. I have read several conversations about the putty box on [continuousWave.com] , but none say what this putty actually is.

The OEM putty sets up really hard, but I do not know if [a replacement putty] needs to have some flex to it.

[Moderator's note: illustrations Figures 1, 2, and 3 were added to this post after several replies were made concerning what was meant by the term "putty box." Also, the through-hull fitting that was under discussion was identified as being not in the transom but in the aft portion of the hull and exiting downward, from the deck level through the space between the bottom hull and liner. The explanation of the illustrations in this post was added in a much later post, but those explanations are now moved to the captions of the illustrations themselves so that the reader who is reading this thread in order from the start can know what he is looking at.]








BACKSTORY
I have been lurking on this forum for a while. I really appreciate all the help this group provides. Maybe someone has an answer for this one.

The livewell water pick-up through-hull fitting seal failed on my 2002 180 Dauntless, and I did not know that they needed to be inspected.

After launching the boat in 2025 the sump pump was coming on every 20 minutes. The seal at through hull was leaking [at a substantial rate].

I removed the bronze through-hull fitting, and there was a little water coming out of the unfilled screw holes for the through hull screen and the place where the putty meets plywood on the bottom of the hull. I pressed on the inside of the drilled hole and the putty was cracked on the uphill side. The hole for the through hull, while on specification with the drawing was drilled only about 1/16-inch from the edge of the putty box, and the the foam on the other side was wet.

I removed enough of the putty that the foam could start to dry. After about a month drilling holes, and applying vacuum, I have the area all dried out, and I am getting ready to replace the through hull, but I want to repair the putty box, and perhaps expand it a bit so there is more putty around the through hull than before. I don't think this is why it failed, but I assume this adds structural support to keep the fiberglass from flexing when the fitting is tightened. I really appreciate it.

I don't understand what you are writing about when you refer to putty or a putty box. Please post a photograph of the part you've described as a putty box.

The term putty box as previously used on this website refers to a section between the outer and inner hull (liner) where the foam has been excluded and replaced with a material that creates a solid and waterproof area. The purpose of this modification at the factory was to provide an area where a SONAR transducer could be installed using a through-hull method rather than attached to the transom.

The term putty box is not a reference to any sort of sealant applied to a through-hull fitting. The typical sealant used by Boston Whaler is often a commercial product that is not generally or easily available at retail or marine outlets.

Replacement of through-hull drain fittings on the transom of certain late-model Boston Whaler boat was the topic of a youTube presentation on the Boston Whaler channel, published about 14-years ago. See

Replacing a Thru-Hull
https://www.youtube.com/watch?v=Zby76eoKO-I

A possible adhesive sealant that could be used is Sikaflex 291 available from Amazon for about $14.

Thanks for the help guys. Lets see if this helps explain it better.



The small drill holes around the factory drilling for the livewell pickup were drilled by me to help get it dried out. The only one that found foam was the one above the factory drilling. The others all found hard, dry cured putty.

[Repeats original question.}

Q1: What brand and model of "putty" was by Boston Whaler for the putty?

Q2: What available material would be compatible with the OEM putty?

I want to beef-up [the area around the through-hull fitting] before I [re-install the through-hull fitting and] re-seal [the openings] .

Absent advice from someone who has previously encountered and resolved this repair, I think I will use MarineTex [a pre-mixed thickened expoxy sold in various size containers]]

I will let the MarineTex cure for a week or so before I apply new sealant, and then I will re- install the bronze through hull with a proper sealant.

The putty box is used in modern boats as an area for installation of a through hull transducer or through-hull fittings. Boston Whaler fabricated this box out of solid fiberglass.

For your predicament, let the foam dry to the touch.

Coat the exposed foam with epoxy and reinstall a new through hull fitting using a quality marine sealant (NOT adhesive) in the fastener holes and the fitting flanges on the interior and exterior surfaces. Recommended brands of marine sealant include Boat Life or SikaFlex.

It is somewhat known that the factory did not install much sealant in the through hull and transom fittings and it often led to water ingress into the foam.

Thanks for adding four illustrations and much expanded explanatory narrative so that readers now understand much better the location of the through-hull fitting (which is noted as being bronze and passed through the hull bottom) that was leaking.

In this instance the through-hull fittings are much the same as a through-hull SONAR transducer, as in both cases there is a penetration of the hull vertically through the laminated structure of the Unibond hull, with the lower opening being far below the water line and also likely that the upper opening could be just at or also even below the water line. Maintaining a water-tight passage and seal for fittings like this is extremely important.

MarineTex describes its product as "a creamy paste consistency that can be applied on vertical or horizontal surfaces." They also state, "Marine-Tex is a heavy-duty structural epoxy, used to repair aluminum, fiberglass and wooden boats..."

The mixing ratio of the epoxy resin to hardener is quite high, 5-to-1 by volume. Generally when mixing epoxy resin with its companion hardener, using exact volumes of the resin and hardener in the recommended ratio is very important, as any excess of either component will remain unchanged in the chemical reaction, and thus reduce the strength of the resulting adhesive created by the process of mixing.

Also, epoxy resins are not particularly stiff viscosity by themselves, so creation of a paste is usually achieved by adding filler material to the resin material or to the mixed resin-hardener solution prior to onset of the curing.

Epoxy chemical reactions (curing) are exothermic, and increased temperature tends to increase the reaction rate, producing more heat. If a large volume of epoxy material is poured into a block or mold area, then the curing process can result in thermal runaway. If this occurs the strength of the resulting cured material is much compromised. For this reason you should use care in mixing and curing a large volume in a single pour.

Another option for a convenient source of thickened epoxy might be the WEST System epoxy repair kits or Total Boat epoxy projects.

GorgeWhaler wrote:...I want to repair the putty box, and perhaps expand it a bit so there is more putty around the through hull than before. I don't think this is why it failed, but I assume this adds structural support to keep the fiberglass from flexing when the fitting is tightened.

Based on what is seen in Figure 4 where you added a red line callout that shows the layer below the gel coat in the cockpit is foam, and presumming the through-hull fitting is tightened by a nut on a threaded portion that extends above the cockpit gel coat layer, then on that basis I do not see how the putty box is going to add strength at that point. Tightening the nut would exert a force on the gel coat layer and the foam layer below it. The putty box is (apparently as shown in Figure 4) below the foam layer at this point. The foam will be more likely to be compressed than the cured putty of the putty box.

The wood reinforcement layer located farther down in the hole is positioned just above and bonded to the hull bottom gel coat layer. The purpose of this layer is to provide material so the screw fasteners (which I presume hold a grill in place over the through-hull inlet fitting) will have material into which they can gain strong purchase.

The purpose of the putty box is to provide a waterproof surrounding layer. It seems a bit paradoxical that the putty box does not extend almost all the way to the cockpit gel coat layer. Your illustration Figure 4 shows the foam layer is between the cockpit gel coat and the putty box.

Regarding making a large hole through the hull that exits below the water more immune to having water penetrating the surrounding foam in the interior of a Unibond, a proven technique is to drill the hole or otherwise enlarge the diameter of the hole to be very slightly oversize, apply a coating or two of epoxy resin to the inside diameter of the hole, decreasing its ID, and then re-drill the hole to the proper size. In this method the foam that was exposed is thereby sealed by the epoxy coating, and any water that exists in the hole cannot get to the foam.

Note that the reason there is a layer of foam above the putty box in the construction of your Unibond hull relates to the sequence of creating the Unibond hull.

The hull is formed from two separate laminated and molded assemblies. The hull bottom assembly is laid up in its female contact mold, and while the polyester resin is still curing, and in the location where a through-hull fitting is anticipated to pass vertically through the hull bottom, a rectangular area is built up using a material called "putty" which cures to a hard solid form. The height of this material is limited because in the next operation, the hull liner section will be laid atop the hull bottom section, and to create the putty box to the precise height of the distance separating the hull bottom and liner sections would be difficult. After the two hull sections are joint, all space between them is filled with an expanding foam. The entire assemble cures while the two components are still in their molds, necessary to resist the force of the expanding foam, whose expansion is limited in order to increase the density of the foam.

This sequence produces the various layers seen in the hull at the through hull location (as are shown above in Figures 3 and 4). Starting from the cockpit deck level and working downward toward the hull bottom, the layers are:

1. topmost, the deck laminated layer
2. foam filling
3. putty box
4. wood reinforcement, then lastly
5. laminated hull bottom.

Once again, I appreciate the help. Thanks folks.

I have some boat life sealant and some epoxy headed my way.

I am going to remove a little bit of the exposed foam and seal with epoxy. Once it hardens I am going to use the boat life sealant to re-seal the through hull area, paying special attention to the place where the the transitions are from putty box to wood and wood to exterior hull.

Once everything is cured up I will re-install the through hull with plenty of sealant, and re-seal the press fit drain fitting as well.