1982 Cobalt 19BR in dry dock

[geneseo1911]

Well, I'm back to working on the old brown Cobalt. I have been chasing a persistent water leak since I bought it, and convinced myself that it was the exhaust system. Fixing it meant pulling the engine.

The old Merc 260 has a three-piece ram's-horn whatchamacallit, and sure enough, the port side had two loose bolts and was almost certainly leaking.

When I pressure washed the bilge, I discovered the inevitable....a 30 year old boat with a rotten transom. In Cobalt's defense, it was not too bad, and was obviously caused by a sloppy transducer installation at some point in the boat's life. That certainly explains the stress cracks.

A little more exploratory surgery revealed the extent of the damage...floor good, main stringers good (phew) foam dry (PHEW!!!), motor mounts good, but the little stringers in the bilge were gone, the fuel tank support (and the little piece of ply that supported it) was gone (this piece was only 1/4 ply and the ONLY unencapsulated piece of wood in the boat).

I'm making good progress. I got all the drive parts out in one weekend, and got all the old wood stripped out in one weekend and two evening. My glass & supplies will be here Tuesday, the Arauco ply, pink foamboard for patterns, and PL Premium were purchased at Menard's yesterday. I hope to get the grinding done tomorrow, and the new transom and stringers laminated Sunday. In addition to that work, I plan to build pyramids for the front seat pedestals so I can have a little better visibility, and seal up all deck penetrations to make sure I never have to do this job again. The deck has pulled away from the starboard stringer, so I will re-tab that back together as well.

All in all I'm impressed with the Cobalt's build quality compared to some other boats I've seen here. They individually encapsulated each piece of wood, which obviously saved the main stringers from the rot spreading into them. This is actually turning out to be a relatively easy project.

 

[geneseo1911]

Re: 1982 Cobalt 19BR in dry dock

I found a little tip for you guys in the process of removing the old transom. Most of it was still good and dry, but had to come out. I eventually defaulted to my favorite tool: My Matco air hammer. It wedged under the edges and a little prying (well, okay actually a lot of prying) popped the pieces apart. Once I started using it, I had the whole transom (and the last sheet was COMPLETELY and STRONGLY adhered to the 'glass) out in about 2 hours. That time includes the final pass I made to strip as much wood off as I could get to minimize grinding. Here's a couple pics:

 

[geneseo1911]

Re: 1982 Cobalt 19BR in dry dock

Grinding's Done! I'm miserable and elated at the same time. This is the low point...the demolition is done and from this point forward she gets closer to being back in the water.

 

[geneseo1911]

Re: 1982 Cobalt 19BR in dry dock

Well, guess nobody cares about the old Cobalt, but in case anyone is following along, I need some help.

This boat has a curved transom. I have nice, flat plywood. Somehow I have to bend 3/4" ply to match the glass. So, how is this done? Should I wet the plywood and clamp it to the transom for a few days? Should I laminate my transom and THEN clamp it in? Should I lay up the transom one sheet at a time? Any other suggestions?

The curve is hard to see in the photos...the back of the trailer is flat. The flat plywood leaves a 1/2" gap against the curve in the middle. I'm using the same the same schedule the factory used...a full width of 1/4", a half width of 3/4", and a 20" wide piece of 3/4" to provide the thickness for the drive mounting.

 

[GT1000000]

Re: 1982 Cobalt 19BR in dry dock

Must of missed this rebuild, with so many going on...
Welcome to the dry dock, geneseo1911... and good looking progress so far...
As for the curved transom...
I have heard of a couple of ways to tackle it...
First is to use several thinner sheets of plywood and sort of make your own curved plywood transom plate by laminating them into the curved hull one at a time by applying pressure from the inside with bracing until you build up the required thickness...
Second way is to make "kerf" cuts in the plywood, fill the "kerfs" with thickened resin after you get the shape you need and seal with resin and cloth...
Third is to somehow steam bend the ply, but I really don't know what would be involved with that...
Best of luck and I'd like to tag along and watch...
GT1M

PS-"kerf" cuts=series of shallow cuts in lumber to allow it to bend...
how to kerf, Kerfing MDF, Bending Wood - YouTube
Kerf - Definition and More from the Free Merriam-Webster Dictionary

 

[geneseo1911]

Re: 1982 Cobalt 19BR in dry dock

Thanks GT. Those are kind of the options I found on the 'net. I went ahead & set up my clamps and pulled on it, but was only able to get it about 1/2 way. The idea of cutting my rather expensive plywood doesn't sound too attractive to me. I was close to building forms and trying pouring boiling water on towels to dampen and bend the ply, but by the time I built the forms I think I could easily cut 3 - 1/4" pieces and glue them together, so that's the route I think I'm going to take. Unfortunately that means another trip to town and that I won't be able to get the lamination done tonight, which pushes the fiberglassing back a couple days until the PL cures. It also means I'll have to build the transom in the boat and get all the sheets glued, lined up, and tighten the clamps before it begins to set up.

 

[Woodonglass]

Re: 1982 Cobalt 19BR in dry dock

I'd use 5- layers of 3/8" ext. Grade Ply and internal wedge clamping to make the curved transom. with the PB and the layers of glass you'll come out with about a 2 1/8" to 2 1/4" thick transom. Are your stringers still in?

 

[geneseo1911]

Re: 1982 Cobalt 19BR in dry dock

Thanks WOG. What do you mean by wedge clamping?

I had pretty good success using 2x4's flatways, which allowed them to flex and follow the curve.

I did go ahead and get 2 more sheets of 1/4". The area around the keyhole is flat, so I can use the 3/4 I cut for that, meaning I just need to replace one sheet of 3/4 with 3 sheets of 1/4.

The stringers are still in, and are perfect. They were completely separated from the transom and and look like they went in yesterday.

This pic is sideways (motor mount is on bottom, fuel tank is up) the hole shows the nice dry stringers and foam, below(right) shows the short stringers that were in the bottom of the bilge, which did rot.

 

[geneseo1911]

Re: 1982 Cobalt 19BR in dry dock

Whew. I haven't posted for a while because by the time I got in from working on the boat every night I was too tired, but I was checking up on the forum, and I thought I should finish out my little thread here. I finished the boat in the first week of August and splashed her August 10. We've been out a couple times, and with the crops being so late and the weather starting to finally warm up (never thought I'd say that in August) we should be able to get several more trips in. It's a good feeling to go out and NOT be taking on water. The transom was still solid enough that I suspect I could've ran it as it was for several years, but the peace of mind of knowing the boat is solid is priceless. I haven't totaled up the receipts yet, but I beleive I came in just under $1,000, including some engine parts, a BIG AGM battery and some wasted plywood and whatnot. I used 7 gal. resin total, 10 yds 1708, probably 3 yds CSM, 1/2 gal. gelcoat (coated the whole transom and bilge twice) and wound up making the transom out of several sheets of 1/4 Arauco laminated together.

This is as deep as I got into her. You can see where I patched an inspection hole, ground for the new fuel tank support, and built a pedestal to raise the driver's seat a little. The other weight is holding down the floor on top of the stringer. As far as I can tell, Cobalt did not screw the deck down to prevent water intrusion. Over time, they separated just enough to squeak when you step in the right spot, so I glued it back down with PB and tabbed them together. No more squeaks!

Here is the new transom after I took it out of the boat. I cut all the pieces, spread with PL, and clamped them in the boat so they would take the curved transom shape. Worked pretty well.

Here's a shot of them clamped in: (one thing worth mentioning here...there is actually the transom proper, and separated from it by a vein of 'glass, is an "upper transom"; which is a single sheet of 1/4" ply that goes up under the cap. This of course was dry, and didn't have to be replaced, which was another reason that the cap could easily stay on during this project.)

And one of the lamination:

And here's a shot that shows the curvature:

 

[geneseo1911]

Re: 1982 Cobalt 19BR in dry dock

I was clipping along pretty good here and didn't take too many pictures.

Here's a shot of the bilge area gelcoated and mostly done. This one shows the construction fairly clearly. Main plywood stringers stop where the engine bay steps outwards, and I assume those little stringers are there to carry the load back to the transom. The board in the keel there is just support (I think) for the fuel tank, as it was only 1/4". I went ahead and stubbed in short stringers on either side of the engine bay just to make things a little stronger. The motor mounts are just a stack of 3/4" ply laminated together, and are the originals.

Here's a somewhat blurry shot of things going back together: (nevermind the toes...)

 

[geneseo1911]

Re: 1982 Cobalt 19BR in dry dock

Finally the exciting time came to put the powerplant back in. Of course, nothing's easy around here. Here's a shot of the rig that did the work (this is the easy way, BTW):

Now, some might notice this is a different forklift than in the early pics. This is actually mine, and the Toyota was a rental we used during planting season, as one of the seals gave up in mine. That meant I had to rebuild the forklift cylinder before I could put the engine back in the boat. That was....fun...if you know these old Clark telescoping cylinders. Not to mention my stupid dog chewed up the $100 seal kit and I had to order another one. But I digress.

This next shot shows the other major project I had to do to get the engine back in. I had a HARD time pulling the engine in the first place because the 36" forks were not long enough to get the engine forward past the shelf molded into the cap. If I had a helper it wouldn't have been so bad, but I was doing it at midnight. I managed to wiggle it out using a couple 2x4's, but it was 3AM before I got to bed. To solve this, I built this boom out of parts I cut off an old NH3 applicator frame we are scrapping. Worked GREAT!

So here's the engine, finally back home:

And the glamour shot (which is admittedly more of the truck....but there's no "i" in team):

 

[GT1000000]

Re: 1982 Cobalt 19BR in dry dock

Excellent news, can't wait to see the wet pics...

 

[Lukie46]

Re: 1982 Cobalt 19BR in dry dock

I have a question for you. I am getting close to gelcoating my bilge area and the keyhole. I see that you gelcoated the keyhole. Did you use poly resin or epoxy? If you used poly resin, did you apply CSM around the keyhole or did you just seal it with resin before you gelocoated? Woodonglass suggested epoxy, but I already did the transom with poly resin.

 

[GT1000000]

Re: 1982 Cobalt 19BR in dry dock

I have a question for you. I am getting close to gelcoating my bilge area and the keyhole. I see that you gelcoated the keyhole. Did you use poly resin or epoxy? If you used poly resin, did you apply CSM around the keyhole or did you just seal it with resin before you gelocoated? Woodonglass suggested epoxy, but I already did the transom with poly resin.

If you are restoring your boat, or even doing some repairs or upgrades, you should really have started your own thread so the rest of the boating community can benefit from your experiences...
That being said, you are A-OK using poly resin if you are going to gel coat...its only if you used epoxy would you have a problem, as gel coat, being a Polyester based material, doesn't adhere well over epoxy...
Most of the I/O builds I have seen just seal the edges with resin, then gel coat...
You could add some CSM to the edge, but I don't think it is necessary.
If you want a little bit thicker coating than just resin, you could thicken the resin slightly with some Cabosil.
Afterwards the gel coat should seal everything up nicely...
Best of luck!
GT1M

 

[geneseo1911]

Re: 1982 Cobalt 19BR in dry dock

I'm paranoid about water intrusion, and the keyhole is the most likely place to get wet in my mind. If everything is done properly, then the weakest link in the chain becomes the u-joint bellows and seals for the trim sender wires and water tube. So to answer your question, yes I did fiberglass the keyhole. I used vinyl ester resin on my project. As GT said, epoxy over poly is fine, and would probably be a good way to go. My understanding is that epoxy is waterproof and strong enough to work as a sealant by itself without needing glass and gelcoat like I did. I didn't want to order another product for such a small job, though. I also wanted the white gelcoat everywhere to make any leaks show up more easily.

I cut the hole just a little big, and when I skinned each side of the transom with glass before I put it in, I folded the mat into the keyhole instead of removing it. I then put a 4" strip around the perimeter folding the edges over. Now this meant I had to do a little grinding to make the gimbal housing slide in, but I still had at least some glass in even those spots, and then I gelcoated the whole thing. I figured the gelcoat would penetrate and clog any pinholes that remained.

I also drilled the bolt holes 1/4" oversize, filled with PB and re-drilled. It worked okay, but I still hit wood in a couple spots. I wish I had some epoxy to seal them, but I pretty well filled the hole with 5200, so they should be okay. I couldn't really go bigger because the bolt holes are so close to the keyhole.

Sorry for the long-winded answer. I love this boat and expect it to last me at least 20-30 years, so I tried to overbuild it wherever possible.

I suspect a LOT of people come here and read through the great information and re-do their boats without ever posting. I bet it's at least 2-3x the number of posted builds. It's kind of cool to think about all the people touched by this site and guided by the work of OOPS, WOG, GT, Frisco, and so many others.

 

[Woodonglass]

Re: 1982 Cobalt 19BR in dry dock

Glad to came back and posted the final results. She looks Great!!!! With the great work you did on her she'll be there for your GrandKids!!!!

 

[Lukie46]

Re: 1982 Cobalt 19BR in dry dock

I do have my own thread (2 years worth). I was just searching "keyhole" and came across this thread. I just appreciate everyones opinions and experiences on their restorations. What works, what doesn't , etc. I am very close to putting my engine back in. I can't wait