How I Repaired Leaking Rivets On My 1975 Aluminum Starcraft Boat

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Steve Hamilton
Posts: 38
Joined: Tue Feb 17, 2015 4:32 pm

How I Repaired Leaking Rivets On My 1975 Aluminum Starcraft Boat

Post by Steve Hamilton » Fri Sep 30, 2016 1:24 am

How I Repaired Leaking Rivets On My 1975 Aluminum Starcraft Boat
by Steve Hamilton

This is from an older posting on our old message board. I thought it may still be of value. I have not figured out how to add the photo's. Perhaps they can be added later.

I have had leaks for some time on my 35 year old 21’ center console aluminum Starcraft named Valhalla. But, with a working bilge pump all has been OK. I always check to make sure it’s in good working condition and replace it when it gets old. The last time out I went perch fishing first. Unbeknownst to me when I grabbed my mudder anchor I pulled out one of the wires to the bilge pump. After several hours of great perching I headed offshore to troll for steelhead. That’s when I discovered the bilge pump was not working. I had some quick action on steelhead, but the water was getting choppy with whitecaps. By now I had at least 3” of water in the bilge. So I quit and went in. A good morning of fishing, but disconcerting about the leaks without the pump. A quick check at home discovered the loose pump wire which was quickly and more securely reattached. The pump works fine again. Knowing that the pump could quit again I started researching repairing the leaks.

The first step was to learn the nature and scope of the leaks. With my boat on its trailer on a level street spot I began filling up the bilge with water from my garden hose. In 10 minutes or so water was dripping from rivets. Some very slowly, some quite fast. With a red magic marker I marked each leaking rivet. There were 19. I pulled the bilge plug and put away the boat. My boat has a permanent floor which I replaced about 20 years ago and is still in good shape being garaged most of the time. That was a major and difficult task I did not want to redo to get access to the back of these leaking rivets,
nor did I want to pay the high cost for a shop to do that.

I called quite a few boat repair shops and followed every lead given. Without removing the floor only two shops offered the same solution; welding the rivets shut. That was estimated to be $30-$40 per rivet. Beside the cost I was concerned about weakening the rivets hold on the interior ribs and on weakening the hull itself. I read a number of online posters various repairs and decided upon a different course of action. Here is what I did.

I bought a 3oz tube of 3M Marine Adhesive Sealant Fast Cure 5200 for $16. It came with a narrow nozzle. It had warnings of dangerous fumes and to avoid skin contact. It also said it started to tack in 15 minutes, cured in 24 hours, and the resealed tube would harden within 48 hours. So I knew I had to use it carefully yet quickly.

I then tracked down some 3/16” diameter Closed End Blind pop rivets with aluminum rivets and aluminum mandrels. Closed End rivets are critical as they should not leak compared to regular open end pop rivets. I bought 100 of them for $10 in Farmington at Jay-cee Sales & Rivet Inc, 800-521-6777. They were very helpful over the phone and in person. I could have done an online order, but wanted them immediately so I drove there. We had decided on size 64, with a rivet length of 0.531 and a grip range of 0.126-0.250”. However their inventory records were off and that was out of stock so I went with size 66, with a rivet length of 0.656” and grip range of 0.251-0.375”. I could have had size 64 with steel mandrels or stainless steel mandrels. The steel would have rusted so they were a no. The stainless were more money so I went with the size 66 all aluminum rivets I wanted. The needed grip range was hard to determine precisely. After drilling out one of the old rivets and using a flashlight I could see the hull thickness and the internal rib material. I did not have a good way to measure that combined thickness. I estimated it to be close to 0.25”.

I worked in my garage with the door and window open for ventilation. I had disposable latex gloves to protect my hands from the sealant and wood tongue depressors if needed to shape the sealant. I had several cushioned pads to lay on, rags for cleanup, and safety goggles for eye protection which was critical when drilling out the old rivets. I used a 3/16” drill bit in my electrical drill to drill them out. It took some care to make certain I was drilling in the center of each rivet. Metal shavings flew everywhere. I drilled out the 19 marked leaking rivets and another one I found with its head sheared off. Then I used a small grindstone in the drill to smooth over each rivet hole and to remove any paint, etc. Then I test fitted each hole with the new rivets. Some needed enlarged to fit. Then I vacuumed up all the metal shavings so I would not be laying in them.

I worked in four different areas of the hull in this sequence to complete each area quickly while the sealant was workable. I got my Pop Rivet Tool ready with rivets laid out. Then I opened the sealant tube and attached the narrow applicator end after cutting it to an opening size which would just fit into the drilled out rivet holes. Working quickly, but methodically, I held the tube into each hole, squeezing in some sealant. It took a few tries to figure out how much squeezing was needed to apply an adequate amount. As I removed the tube from the hole I made sure to apply a small amount of sealant to the outside rim of the hole where the rivet head would make contact. Then I jammed in a rivet with the pop rivet tool and squeezed it numerous times, holding it firm up against the hull until the mandrel snapped off. They seated firmly.

After this was completed in each of the hull sections I then applied a very small amount of sealant on the top of each rivet head and made sure a small seal was all around its edge. Then I wiped off the excess from the hull. I am not sure if this final sealant application was a good idea or not. The rivet head shows a hole where the mandrel snapped off but being a closed end inside it should be watertight. I thought it wouldn’t hurt to cover it lightly. But, the plain rivet head was clean and had a nice appearance. And the sealant may add a very tiny amount of drag. I may try to get some matching hull spray paint to touch it up. As these rivets are under the waterline they’re pretty much out of sight even on the trailer. This whole process took about 3 hours.

Now to give her an in the water test. My goal was to eliminate at least 75% of the leaks. As I had 3”+ in the bilge after 4 hours, that size reduction would be great.

The test was passed!!! I spent almost 6 hours trolling and did not run the bilge pump because I could not, as it was never under water. There was less than 1" of water in the bilge. Success!

Steve Hamilton
Posts: 38
Joined: Tue Feb 17, 2015 4:32 pm

Re: How I Repaired Leaking Rivets On My 1975 Aluminum Starcraft Boat

Post by Steve Hamilton » Fri Sep 30, 2016 1:28 am

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