TOPIC: 1968 Duo Boat Restoration

Hello All!

I am looking for some insight as I restore a 1968 Duo Boat (pictures attached). I have completely gutted the boat and I am confused by the design of the bilge area. Water seemed to actually build up around the bilge area instead of actually being able to pour out the transom drain hole. The transom drain hole is surrounded by a short wall of fiberglass making up the bilge(picture attached). I am wondering if I should replicate this design as I restore the boat. Appreciate the feedback.

Welcome aboard. We're here to give you the best advice possible....as seen by members.
That is a PROJECT to be sure. I would start by cleaning the whole bilge area out, grind down all the fiberglass that is sticking up so you just have a clean slate bottom. You should separate the top from the hull but before you do that put some bracing in the hull so it will not spread apart otherwise you'll never get the top half to fit back on properly once you glass in a new floor. As far as the back drain hole is concerned as you suspect there has to be a free flow space for water to run from front to back. If you put in cross ribs you will have to put at least a 2" hole down the keel line in each rib. If you run framing front to back lengthwise leave an inch or two near the transom so water will flow front to back and then drain into the lower transom area by the hole. There are lots of threads on this side that will give step by step how-to's. Just ask.

Appreciate the feedback! Yes definitely got a project ahead of me haha. I attached some more photos as well. Hopefully I will be done gutting the boat this weekend. Unfortunately I already took the top off but did not brace the hull. I am going to use ratchet tie downs to keep the sidewalls somewhat close to the original shape of hull when top of boat was connected.

Hi there, I have restored a DUO before, and my advice is to rebuild the transom. Then reattach the cap to the hull to reestablish the shape of the hull, then rebuild the floor. I have had the same debate with myself over the hole in the bilge well to let water escape from the under floor area. If you build the floor right there should never be water between the hull and floor so there is no need for a drain hole, but if water does get in there it has no way of getting out without a hole in the bilge well, but if you put a hole in the bilge well it will most certainly allow water into the stringer area which you are going to want to keep dry. So you make the decision, one boat I made a hole in the bilge well wall to drain the stringer area, and the other one I didn't. I figure the one I didn't I can always drill a hole to let any water out later, or maybe you could make a hole and then put a drain plug in it to stop any water in the bilge well from entering the stringer area, but still have an option to drain it should water get under there. That is a lot of run on sentences. Remember also the air space under the floor a lot of times was concidered your flotation to keep the boat from sinking should if ever get flooded, I'm not saying it would actual work but something to concider. Hope this rambling helps.

A friends boat from the 80s had small removable rubber plugs in factory holes as suggested above. He would pull them out after a week vacation in the water because he had dripping wet water skiers in the boat all week. Seemed like a reasonable idea and assumed they otherwise stay plugged for possible floatation considerations. Your original design looks like it assumes a good floor seal that wasn’t supposed to ever let water down into the stringers and assumed all water in the boat would run off the top floor and only drop into the dammed off drain well. My floor was sealed but flat wood above stringers rotted because all of the screws someone drove into the floor were never sealed and that seat base wood trapped water from every water skier over the years... one day I had to step on floor under seat and floor breaks through from the rotted wood. However, when I opened up the floor, everything underneath including stringers was still dry. I think original layup was sealed and then they previous owner turned it into Swiss cheese with screws and different boat seats and never sealed the screw holes. Maybe it would have never rotted if I didn’t have wet waterskiers climbing in for 20 years. Good luck with your decision.

I took these pictures of the bilge area of the 1972 Thunderbird Cathedral Hull Outboard boat I recently picked up. Since it is a big hull, it has a glasses off bilge are that has holes with removable plugs to the underfloor stringer area on one level and a lower center removable plug inside the boat walling off the underfloor from the bilge. Picture of this one is from back of boat bilge facing forward . Here are pictures of them removed. These are factory. Hope this helps you in your decision making.

Thanks! I will definitely consider the removable plugs as a possible solution. As much as I would like to believe I can duplicate the deck design perfectly (air tight) I want to be realistic. I just don't like the idea of water not having a way to escape if it were to get under the deck. I probably will use removable plugs.

In other news, the boat is now completely gutted! Now plans for a new deck and transom begin.

When I removed the transom multiple hard nubs were left (pictures attached) connected to the hull wall. They almost seem to be a part of the hull. I cannot determine whether they are made out of fiberglass or some other material. Do any of you have any experience with these things? My concern is when I go to install a new transom. Not sure how i am going to be able to install a new transom with these nubs attached to the wall.

I am not familiar with those, so hopefully others are. Could you use cardboard as a template and let those punch through... then use that pattern on the first rough fitting of the first plywood laminate for a dry fit by marking and drilling holes a bit larger. Then once things are all dry fitted and you dry fit the full laminated transom, you could fill holes with a peanut butter consistency when also coating for full transom install and I would think it would ooze out as it filled all voids. Maybe others even have much better ideas. I don’t have those on my small boat with rotted transom removed.

Almost looks like a repair to me ? Wonder if someone drilled out a couple of screw holes and filled them with epoxy ?
Since you plan on sanding the outside anyway ? Hit the outside glass with a sander in that spot to see if it looks like a repair ?
If it were me ? I'd cut one off to see what's inside ? If it's an epoxy repair ? I'd use my harbor freight multi-master, and get rid of them... the less sh-tuff in the way when putting in a new transom the better. Just my thought ?

Amen Chuck.

That makes way more sense. Now that you guys helped me understand what those might be, I could also see potential future trouble spots if they stayed. With such small adhesion area, I could see if they were left behind and they got bumped around just enough during repair that they outside could develop tiny cracks around the which could lead to water weeping in and als would not leave much outside contact area to seal compared to what Chuck recommended to remove them. Thanks Chuck as I learn more every day on this site.

Does anyone have any recommendations on certain brands of fiberglass resin for transom plywood before installation? This would be the resin i cover the plywood with and let dry before applying the thicker resin when I go to install. Appreciate any ideas! Thanks

laminating resin (no wax) to build your layers and finish (with wax) last coat. i did not use ply, composite mix instead but you would still coat the ply, roll and layer the glass in similar fashion. Then tab in the perimeter. I had some guidance from the composite company and a local club member. video link - www.dropbox.com/s/6kmvby4jew1ktp3/L%20%26%20S%20Part%20I.mp4?dl=0\

picture shows the 2 part faring compound going on the exterior over a layer of chop strand.

Search the forum for transom replacement. I believe there are pictures of plywood projects posted.