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

[Axhammer]

The hull was full of leaves, and dirt under the seats. I blew most of it out with a leaf blower.

I raised the trailer tongue so the hull would drain, and pressure washed the interior and exterior. The interior metal looks bad, because it is discolored and lots of little missing paint specks, but I didn’t find any corrosion…so that’s a good thing!

Other than the cracked ribs I was already aware of, I couldn’t find any more cracks or damage that will require a repair. What’s left of the front deck may still come out, I haven’t decided yet

I spent several hours pressure washing the boat, I finished up as the sun was setting, so no pictures after pressure washing.

 

[Axhammer]

When I started this thread, in the title I mention this is my “first tin boat project”.

I guess I misspoke…in 1987 I bought a Aluma-Craft run-about, but I don’t remember what year the boat was. I only have one picture of it from the day I bought it. This picture is at my buddies house where I took the boat to show him. He had the same engine on his bigger wooden fishing boat, with a kicker on his. This was in Port Angeles WA. It was a Great Lake Boat for water skiing, which I did every summer on Lake Sutherland. When I transferred in 1990, I sold it to another buddy.

I repainted the hull, my buddy reupholstered the back to back seating for me. With new upholstery and carpet the interior was pretty nice. I polished the plastic windscreen which turned out pretty nice. I had the trailer sand blasted, and repainted it with new lights.

In the end I had a great low budget ski boat, with a 1969 Evinrude 55 three cylinder that would pull me up on one ski. I would guess the boat was a late sixties or early seventies model year. To put it in perspective it was 1987, and that boat was about twenty years old.

 

[Axhammer]

Back to my 1751 tunnel hull duck boat.

The hull interior condition looks worse that it is. I haven’t found any corrosion. The metal is thick and structurally sound except where cracked. The rivets are tight and standing the test of time. The transom was flexing and cracked the rear seat flanges, where attached to the hull skin. The rear seat assembly in this type of boat is a structural member, adding strength to the design.

I am planning on building an aluminum replacement transom, and framing it in to the rear seat. My rear seat will more about reinforcement to the transom, than a seat. I’m not sure how the final product will end up, but it will be stronger than the sheet metal support the factory used.

I am going to break this project into three main sections. Floor, Console and Transom.

I will fix the ribs and install the new floor first, including upgrades to the front deck. This way I will have a floor to walk on while framing in the transom and rear seat.

My center console will have a passenger seat built in, the lid to the live/bait well will have a cousin on top for seating comfort. My design will be long enough to straddle the cracked ribs. My console will add structural strength to the original design. My center console design will be finalized before putting the floor down, because the console will tie into the floor…all will be designed for added structural strength.

I will post a picture of another boat with a white center console, like I want to build.

 

[Axhammer]

When we were test running the engine last week, we noticed water leaking into the boat on each side of the forward tunnel structure. This may require the seams to be welded, I’m not sure yet. It seems odd they are not fully welded at the factory. If they were not fully welded from the factory, and it didn’t leak when new, why is it leaking now? I’ll post a picture of the two leak areas.

I think I need to flip the hull upside-down, after the motor is removed to inspect the entire hull bottom, and especially the tunnel part of the hull, before moving forward with this project.

That water is coming in from somewhere.

 

[Axhammer]

For those who have never dealt with solid rivets, I will talk about how I removed the rivets that were attaching the various parts I have removed.

The rivets I removed were 1/4” (.25) Brazier Head rivets.

I drilled each rivet head with a new bit smaller than 3/16” (.187), probably closer to 1/8” (.125). I simply grabbed a new bit out of my drill index to drill the pilot holes. I drilled these holes as close to the center as possible, and deep enough to assure it was deeper that the thickness of the rivet head. It is important to drill straight perpendicular holes.

Next, I drilled each rivet with a 3/16” (.187) bit, again deeper than the head of the rivet.

Using a 3/16” pin punch I stuck the punch into the hole, and pried each rivet head side to side until each head popped off.

I used vice grip pliers to grab and break the bucktails off the backside, leaving a clean hole.

When I install the new rivets I will “wet install” each rivet with a sealant/adhesive. The sealant will be applied to any permanent part that I rivet together on this boat. When this boat was assembled at the factory when it was new, they did not wet install anything, I guess that is the industry standard. In the aviation industry parts are wet installed for several reasons, like added strength, and corrosion resistance.

I bought several different brand adhesive, or sealants to conduct a test. I will bond three different identical parts together using 3M 5200, Red Devil Strong-Bond 0956, and West SystemG/flex 655 thickened epoxy adhesive.

I want an adhesive that has a slight rubbery characteristic when cured. It will be strong, and hold up to stress and vibrations in a marine environment. I know 5200 is kinda the go-to adhesive for marine applications, but I prefer an adhesive that has a firmer feel when cured. I’m looking for something similar to 23699 used in the aerospace industry, but cheaper.

We will see…

 

[Axhammer]

Deleted

 

[billz]

Thanks for describing how you drilled out the rivits, this will help me. I will have to do that in a few weeks on my boat project, I was going to grind them off but that would cause unnneeded damage.
Looks like you are making progress, the small steps of a project.

 

[Axhammer]

I have four different brand adhesive’s curing.

I glued aluminum coupons together, after grinding with a flap disc, and cleaning each with acetone.

I put on approximately the same amount of each adhesive and clamped them tight enough to get good contact, with plenty of squeeze out. I am trying to duplicate a boat part being installed “wet” with adhesive.

After they are cured, I will try to twist them, and pull them apart by hand.

We will see how it goes.

 

[Axhammer]

After allowing time for the glue to cure, I started handling my test piece.

The G-flex adhesive is on the left, and is amber colored. It is the only one that is a two part adhesive that must be mixed, it is hard and rigid compared to the others. G-flex is the most expensive.

The other three brands (gorilla glue, 5200 and red devil) are white, and no mixing is required. The three white adhesives have a rubbery character after cured, and seem to be about the same in rigidity.

When grasping each end of this 12” long test piece, I cannot twist or bend it. It is very rigid and strong, it seems like the aluminum may bend before the glue fails.

 

[Axhammer]

Using my hands only, the part did not fail.

I was trying to bend the test piece over my knee when it eventually failed. The GG failed.

I am going to clamp each piece in my vice next, and try to bend and twist until the next failure occurs.

I drove up to Norfolk to buy some aluminum sheet, tube, angle & rivets for my tin boat project. I bought my aluminum from Matt of “Tricked Tins” or PW-MARINE.COM

Check him out on YouTube.

 

[Axhammer]

I made an engine stand for my 1992 Evinrude 60 VRO.

I removed the engine from the boat, and bolted it to the stand, and rolled it next to my 1980 Jonson 75 Stinger.

Tomorrow I need to clean the shop, and back the boat in and lift it off the trailer. I want to flip the hull, and inspect the tunnel seams, and figure out why water is leaking in.

I need to inspect the underside skin and all the rivets, before flipping in back over for the rib repairs, and manufacture a new transom.

While I have it off the trailer I want to inspect the trailer, and figure out how to lower the bunks. The way it’s set up now, the hull is sitting above the trailer fenders, with the bow sitting lower than the stern. It’s kinda backwards, because if you don’t run the tongue jack up all the way, it will fill with water if it rains.

 

[Axhammer]

I’m going to post a couple pictures of my 1751 sitting on the trailer that it came with.

In these two pictures I’m towing the boat with a Jeep that has 2” lift & 35” tires. I mention the Jeep because the way the boat sits on the trailer, it is sitting “bow low”, despite being towed by a vehicle that sits higher than average.

When I towed my Ranger BB (on a Ranger Trail trailer), with the same Jeep, the Ranger sat with the bow slightly higher than the stern. I know I can simply use a different hitch, to raise the front of the trailer/boat, but if I were to do that, and then tow my 1648 with the same setup, it would be way to high in the front…the 1751 just doesn’t sit right on this trailer.

My initial thought was to use a difference trailer, but I haven’t made up my mind yet. I have a galvanized trailer that was originally under a Ranger BB, that I could modify to work with this boat, so I have that option I could fall back on later.

One thing I don't like about the trailer that came with the 1751, is the length of main square tube that connects the trailer to the hitch, is so long that is sags. When I look at something, and I see it sagging, it drives me crazy because that’s all I can see…I can’t see the forest because of one crooked tree…LOL.

 

[Axhammer]

When I was cleaning the boat, I was towing it with my CJ-7 that isn’t as tall as my newer JLU.

Towing with the CJ-7, the 1751 sits bow low. If it rained the front of the boat would hold water…not good.

To raise the bow to allow drainage while pressure washing, I drove the rear tires of the CJ-7 up on some blocks, and it was still not draining. The boat was almost level, but it was still to low up front.

I eventually lashed the trailer tongue to the spare tire rack, to get the boat to drain.

 

[Axhammer]

I just went outside and looked at it closely. The only part of the 1751 that is supported while on the trailer, is in the back where the boat is resting on the bunks. The bunks are 2x4’s on edge, about 4’ long at the most.

The keel of the boat is not resting on the centerline rollers like it should.

I have come up with a plan. I will remove the trailer fenders, because they are close to the boat when loaded, and I want the boat to sit down in between the fenders. In the end the fenders will be moved and modified as required.

I will make new bunks that are lower on the trailer. I will adjust and set it up so that when it’s on the trailer, it will be supported or sitting on the centerline rollers, and the bunks, with the weight evenly distributed.

It will also be sitting with the bow higher than the stern for drainage when I do this.

I want to be able to leave the boat attached to the jeep, outside overnight and not have to worry about a thunderstorm filling the boat with water, because the boat doesn’t drain.

 

[Axhammer]

This trailer has a receiver for a 1 7/8” ball. I will replace it with one for a 2” ball, so I don’t have to swap balls to tow the boat. I have other trailers with a 2” ball.

I am tempted to shorten the main beam a foot or two, because it is too long. I haven’t made a decision yet, because once you cut it, it’s a done deal.

I don’t like the way this main beam sags. You can really see the sag in the side view picture below.

Does anyone have an idea that will address the sagging trailer?

 

[Axhammer]

I lifted the 1751 off the trailer and set it on three furniture dolly’s in the shop, this way I can move it side to side for better access while I work on it. I have three cracks I need to weld. The cracks were easy to see after turning the hull upside down. The tunnel sheet metal is all one piece, and welded around the perimeter & riveted as seen in the pictures. There is some light to moderate corrosion on and around some of the rivet heads. I tap tested all the rivets and I didn’t find any loose ones.

The galvanized trailer has a funky cross beam welded in place, where the main tongue beam attaches. The beam was welded in crooked, making the beam appear to have a twist. I think I can make this trailer work.

The transom was gasoline soaked, it smelled for a couple hours as it drained and evaporated.

 

[Axhammer]

I cleaned up the cracked areas using a 4” rotary wire wheel, and started on the rivet heads as well. My cheap HF grinder started getting hot, so I called it.

I guess my boat is getting a new paint job.

What kind of paint are folks using on their jon boats?

I plan on keeping it the same basic color, and applying the paint with a roller.

 

[Axhammer]

When I pushed the boat into the shop I accidentally broke my test price, that was clamped in a vice on the floor.

The 2200 failed this time. I wasn’t paying attention when it happened, so I might have snagged it in such a manor all the stress was put on the 2200 bond alone. I guess it’s not a controlled test at this point, so I’ll just go with it

G-flex
Red Devil
2200
GG

The G flex and Red Devil are remaining at the top of the list.

 

[lckstckn2smknbrls]

Two things
1) Get a hitch with a several inches of rise to level out the trailer when towed.
2) You can weld a length of angle iron to the underside of the tongue to control the sag.

 

[thill]

That kind of trailer is pretty light-duty, but if you could easily lift the boat off to put on dollies, it should be fine for a boat that light.

When I'm in your situation, I will generally adjust the bunk support brackets so that when the trailer is level, the boat will be sitting slightly bow-up. It depends on the brackets that trailer uses. I don't like to use a keel roller to accomplish this, as it can cause undue stress on a single point in the hull.

I hope you can get it right.