1992 Polar Kraft MVT-1751 with a 1992 Evinrude 60 HP…my first tin boat project

[Axhammer]

After grinding the welds I took a flap wheel over everything lightly. It feels pretty solid now, my ugly welds are working…lol

I am learning how to weld aluminum, one way or another.

 

[Axhammer]

I welded the cracks at the forward corners of the tunnel section. The cracks were mostly running parallel to the welds, close to the factory welds. After I finished the cracked corners, I was planning on welding the cracks adjacent to non factory welds that are on the tunnel walls, on each side. These cracks are very close to the welds also.

I was hoping to finish the welding on the hull exterior yesterday, and I would have most likely until I ran out of argon. I will to be more attentive to the total PSI in my bottles. Running out of gas on a Sunday is a show stopper.

I’m not sure why the additional welds were completed, but I suspect a previous owner was trying to fix the floor flexing. I will discuss this more, I have my suspicions but I am definitely not sure why these additional welds are there.

 

[Axhammer]

Like a said in the previous post. I have questions to ponder…

Why did someone weld the tunnel skin to the ribs on each side of the tunnel? They welded four spots, two on each side. There are four ribs on each side of the tunnel. Why didn’t they weld all four on each side if they thought it needed the additional strength?

I’m pretty sure they only welded what they could get to, without removing the rear seat.

These boats don’t normally crack, and when they do crack, there is usually a reason.

I know for sure, the floor on this boat was flexing up & down at the cracked ribs.

I believe this boat had a plywood floor when it was new. A plywood floor would help strengthen the hull bottom because it would tie both together, where the floor & hull is attached. I believe maybe after a couple decades the wood floor might not have been adding to the strength because it was probably starting to rot.

Add in the fact the boat had a 60 hp engine on it for the last ten years at least, vice a 40…now there is added stress from the engine.

I will post pictures of the added welds that are not factory welds.

These cracks adjacent to the non factory welds are what I couldn’t weld yesterday, because I ran out of argon.

 

[Axhammer]

This is what it looks like underneath, before I sanded the paint off.

Red lines depict cracks.

The white stuff is 5200 around a rivet.

I am thinking about cutting the welds on the interior, where the welds attach the ribs to the skin. The factory didn’t put any weld here, I think I could weld the cracks closed on the exterior to stop any leaks, and then cut the weld attaching the skin to the rib inside. I don’t think these welds ever did much to strengthen the floor or tunnel in this area.

I’m not sure what I will do…time will tell!

 

[JL8Jeff]

I wonder if those welds on the beams was just to prevent potential rattling/vibration of the cut beams. I have a Lowe 1652 jet tunnel so it's shorter and not as tall but it looks a lot cleaner. Most 1652 boats are rated for 50 tiller or 60 console so I don't think it was overpowered. I have a 60/45 jet on mine.

 

[thill]

How did I miss this thread? Good looking stuff! I need to go back and read

 

[Axhammer]

Jeff, I like how low your drains are on your tunnel boat. Mine sit a little higher. That’s why I put the bunks on the trailer at such a steep angle. I want the boat to drain when it is on the trailer.

When I’m out crabbing in my 1648 tiller boat, I can pull the plug while running and it will drain pretty well, and it’s easy to do the way the seating is. Access to the drain plugs in my tunnel boat is not good, it is kinda hard to get to the plugs. Pulling the plugs while underway, would not be something I would want to do, unless I was taking on water or some kind of emergency.

I’ve been planning on running two bilge pumps, one on each side adjacent to the plug location. What are your thoughts on this? Do you run bilge pumps, or am I overthinking this?

I do plan on pulling crab pots with this boat, so I know water will be coming in.

 

[JL8Jeff]

My boat has 1 bilge pump mounted right above one of the drains. Water from the other side will flow across the tunnel so 1 pump works for me. When I get to the boat, I usually get in on the side with the bilge pump and the water runs over to the side to pump out. Your tunnel is taller so you might have more of a buildup on the opposite of the pump if you run a single pump.

 

[Axhammer]

I finished welding the tunnel cracks.

I ran a couple practice beads on a .125 coupon.

Next, I welded a couple of used coupons together, running an outside corner bead.

I did two of them.

 

[Axhammer]

Welding the boat sheet metal is difficult compared to welding coupons.

I can’t simply run a bead, if I’m not careful it will burn through.

I don’t know how to describe it, but I end up with huge mountain welds. It seems like the old metal has impurities within, even if I wire bush it and clean it with acetone, it still goes crappy.

I’m sure they are plenty strong, but they don’t look nice.

 

[Axhammer]

I flipped the boat over and set it on a couple flat moving dollys.

I want to lift it onto the trailer and put a few inches of water inside to see it it leaks.

 

[JL8Jeff]

Leaks might not show up by putting water in the boat, sometimes they only show up when the boat is in the water. I had a Boston Whaler jet boat that was getting water inside when sitting in the water. I brought it home and put water inside overnight to look for the leak and not a drop came out. I put it back in the water and was finally able to see it leaking past a seal near the driveshaft. My guess is the weight of the boat in the water puts more pressure on the weak spot. Just something to think about before you button everything back up.

 

[Axhammer]

I put the boat on the trailer and parked it in the driveway. I installed these bunks with an uphill slope on purpose to help water drainage while the boat is parked on the trailer.

The first thing I did was put a running water hose in the boat to see how much water will remain inside the boat while attached to my Jeep on level ground (with the plugs removed). I rinsed the interior starting in the front working my way back, allowing water to drain. The drains on this boat are about an inch higher than they need to be.

 

[Axhammer]

I picked up a used Tempo plastic gas tank, PN #640030, 17 gal. It’s about 17 years old, but it looks real nice, so I bought it for $80 from CL.

I’m planning on mounting it under the drivers bench seat. This will put the tank close to the CG. Handling characteristics shouldn’t change much as the weight changes depending on how much gas is in the tank. I was looking for a 12 gallon tank, but i came across this one. I’m redesigning the rear seat already, I may as well make a mounting bracket, under the seat sheet metal.

 

[Axhammer]

I have the boat hull back in the shop, on the floor so I can access the bottom.

My leak check revealed two leaking rivets. I will try and get them replaced tonight so I can leak check it again tomorrow. The reason I say “try” is because I am alone, and bucking rivets like these normally take two people, one to hold the bucking bar, and one to drive the rivet with the rivet gun. I’m going to set the boat on my dollys right-side up, and make a steel tube that the revet set will slide into. I will make it the correct length so that when it is in place, the river set will be supporting the rivet head from the underside. On the top, or inside the hull, I will buck (smash) the rivet with a hammer, creating a bucktail.

I’ve done this before on the flight line at ATC Mobile, so I know it can be done. We found a small hole in the helicopter hull, and we filled the hole with a rivet, and sent it on the morning flight. Had we towed the airplane into the hangar to install one rivet, it would have missed the morning flight.

I’m gonna touch up some of my welds also.