2002 1436 Alumacraft and floatation pods

[SteveBob]

Hi all, I'm totally new here. I'm looking at installing floatation pods from Backwater onto my 2002 Alumacraft 1436 jon boat. I have ordered the pods and installation materials and should have them within the next 2 weeks or so.

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The motor obviously is too large for such a small boat 2017 20 hp Suzuki 4 stroke at 106 lbs. But rather than replacing the motor, I opted to install pods instead. Beavertail and Backwater sell very similar pods. Beavertail or their retailers did not have the size I needed in stock and had no idea when or if they would. So I opted for the Backwater version.

I have seen these type pods mounted in multiple ways. I had to come up with an easier and less expensive installation means than what I have been able to find thus far.

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But the big question was "how"?

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The price of welding them on was more expensive than the boat was worth, Pop rivets seemed pretty weak to me, I was not going to cut a huge hole in the tops of the pods in order to bolt them on, and there are no marine adhesives I could find that are strong enough to bond the pods securely to the transom on their own. So I decided to go with waterproof closed end 3/8"-16 rivnuts in the pods and then bolt the pods on with stainless 3/8" bolts & washers and then seal the project up with 3M marine adhesive. The whole cost installed complete with a rattle canned paint job will be less than $500 for the pair (pods included). It will take about 2 weeks for the pods to arrive, but once here I'm thinking maybe 2-3 days of prep, install, and paint before being water ready. I'll start posting pics as I progress once the pods arrive.

The pods I'll be using will provide about 118 lbs of buoyancy per the dealer, right at the transom and will add approximately 2' in length to the boat. The buoyancy should more than compensate for the complete weight of the motor 106 lbs. So "empty" the boat with pods, 3 gallons of gas, and motor should float as if it was just the hull in the water with no motor. That alone will make the install worth the investment. Their length should have a similar effect as putting wheelie bars on a dragster. Thus getting on plain a little faster while keeping the front end lower at speed. That and the main point of raising the transom higher in the water to prevent swamping when stopping too fast, backing up, or just rough water as it wants to do as it sits now.

Comments? Opinions?
Steve Bob

 

[SteveBob]

I ordered my pods on the 13th of August and according to UPS, they should be here tomorrow. Right at a week.... That's great. Now all I need is my rivnut installation tool to arrive and I'm in business.

 

[gogittum]

You might want to buy some rivnuts and fool with them some before committing to using them on your project. My experience with the things has been dismal over many years. As long as they are new and clean and you don't tighten them too much, they do OK.

If the threads are even a little bit rough or a "little bit" of corrosion or grit gets in there, they'll spin and removal will become a drill-out project. That can be extremely awkward in tight places and is a major aggravation at best. If you over tighten them and bind the threads a bit, you're sunk. I've spent many hours upside down and backwards under a machine and swearing at the jerks who installed those things.

I owned and operated a restaurant service business for many years and have seen many weird and wonderful things.....and I will NOT use rivnuts in anything I'm working on.

 

[gogittum]

Couple of thoughts came to me about this. 1st, I'll stand by my comments on rivnuts. Hate those things.

I've recently finished a refurb of my 16 ft Starcraft Seafarer and had to pull a seat to mount the folding grab bar. When I did so, I found several broken off rivets that had been holding the seat to the hull. Then, of course, I had to put the seat back in. Like you, aluminum pop rivets didn't appeal to me because of the stresses a seat can come under.

As an experiment, I tried 3/16" aluminum rivets with steel shanks. Those are a whole 'nuther ball game and they are "very" strong in shear. I wouldn't trust them in tension, especially in aluminum, 'cause I think they'd just pull out.

The 3/16 steel are great but a ***** to pull. With a standard pop rivet tool, it took everything I had with both hands and gloves on to pull just a couple of them, then a handle on the puller bent under the strain

I built a small airplane (Kolb Mk III) 20 years ago and became very familiar with Cleco temporary rivet clamps. For the boat project, I bought a new cleco plier and a dozen 3/16" clecos. They were perfect for aligning things preparatory to riveting.

I have a compressor but didn't want to spend the bucks for a pneumatic puller for just a dozen or so rivets. Then found a heavy duty manual puller at Harbor Freight for $20, (all the others were '$50 or more) so drove over there for a look-see. I was greatly impressed. Yah, yah, I know, made in China, but sometimes......??

This tool is 18" long, heavy cast iron and even has a catch bottle for the pulled stems. Very nicely machined and very rugged looking. I brought one home. What a joy to use. It snapped those heavy steel rivets like cheese and they are "tight." Only problem is in tight corners - pretty big, awkward tool and the arms spread wide when getting a grip on a rivet. I'm keeping my eyes open for a larger, more capable standard config puller for those spots in future.....if ever.

While I was at it, I bought some sealed end, waterproof 3/16" steel shank pop rivets for the seat to hull connection and they did a very good job.....and they don't leak when I've got it out on the water.

Final thought - you don't want to spend the big bucks to weld the pods on and don't want to cut big holes to allow bolting. Don't blame you, but how about having the welder weld tabs onto the pods, then bolt the tabs to the hull....with appropriate sealants....?? Seems to me that would solve everything.....??

 

[SteveBob]

You might want to buy some rivnuts and fool with them some before committing to using them on your project.

Thank you for your well thought out reply. "Fooling with them" is already in the plans, I have a small sheet of aluminum about the same thickness and type of aluminum as the pods. I was going to test several of the rivnuts for fitment, water tightness, and resistance to twisting on axis. Also the rivnuts I purchased are stainless steel and have closed ends and beveled flanges with a small *** to help prevent twisting. These were more expensive than most rivnuts and are supposed to hold better than the standard rivnuts you can get at the local hardware store. I am considering denting the pod to accommodate the *** then putting a little jb weld on the flange between the nut and pod to assist with waterproofing. The nuts are not the bulge type but rather the drawn into the sleeve type for a much stronger bite and hold.

Yay the pods and my rivnut tool just arrived while I was responding to this.

 

[SteveBob]

Final thought - you don't want to spend the big bucks to weld the pods on and don't want to cut big holes to allow bolting. Don't blame you, but how about having the welder weld tabs onto the pods, then bolt the tabs to the hull....with appropriate sealants....?? Seems to me that would solve everything.....??

As I mentioned in my last post the pods and tool both just arrived. Also I have a working knowledge of dealing with these critters. I just unpacked the tool and found it is simple to use. The rivnuts are steel but using the tool was not too hard. I compressed one of the 3/8 nuts and although not super easy, all it took was a firm pull with both hands. But its not a typical pop rivet gun, even if it works on the same principle. It has two opposing 15" steel arms/handles that look to me like the ones found on a bolt cutter and they give it great leverage.

Your idea of using welded on tabs is an option I am also contemplating if the rivnuts don't work. But If I don't have to go to a welder, I would prefer not to. Aluminum welders around here are few, not cheap, and they all have a huge backlog.

 

[gogittum]

Good. Sounds like you're going into it with your eyes open.

 

[SteveBob]

I have had a lot of time to think about it..... LOL!!!!

 

[CedarRiverScooter]

Another idea would be to attach them temporarily so you can tryout the boat's new handling.

Some sort of adhesive , epoxy or urethane, will hold them for a while. I did this for my homemade wood/foam ones & they never pulled loose. i had to chisel them off. Didn't hurt the hull at all.

I would tie a rope on them during the test phase, JIC.

 

[eeshaw]

I think you need to revisit your application of the riv-nut idea. I install pods on a lot of boats and make them from scratch. I did some for a 1436 a couple years ago and what I did was install them with backing plates (1/4 inch thick) on the inside of the transom. These pods were through bolted to the transom and had an access hole on the underside of the pod. I also installed them with 3M 5200 adhesive between the outside of the transom and the pod. This is a pretty bullet proof way to mount them. If you go to Beavertails site they have instructions on how to bolt pods in place.

 

[SteveBob]

I said I do not wish to cut big holes in my pods.

 

[onthewater102]

However you finally decide to attach them, I would set them so the underside is at least an inch above the bottom plane of the boat so they're not creating drag when you're full out on the motor.

As for attachment methodology, I would use closed end blind rivets and sealant to attach angle to the pod, then bolt through the angle to the transom to attach them to the boat if you're doing this without a welder. I would use 2 sections of angle per pod, one along each side of the pod (IE no angle along the top or bottom).

If you set rivnuts in the pod and bolt through from the transom you're going to have a difficult time keeping water out of the pod.

 

[SteveBob]

These pods already have the angle built in. So they will mount flush with the transom. The rivnuts I'm using are blind and are closed on the blind end making them waterproof. I intend to install the rivnuts into the pods.

Then I will put bolts through the transom and into the pods. I will not be putting the rivnuts in the transom. I will then seal around each rivnut, along the outer edges of the pods, and at the bolt holes in the transom with heavy duty marine adhesive/sealant. I cannot understand why some of you think this will not work. If you still think it will not work, please tell me why. What is the mechanical justification for failure of this setup? If it will leak.... Why - Where? If it is not strong enough Why - How? I'm reasonable and open to any common sense responses.

I was otherwise occupied, so I have yet to perform any installation of the pods thus far.

Thank you.
SteveBob

 

[onthewater102]

The threads on aluminum rivnuts are very weak and will strip out. It's very difficult to set them without the threads stripping, let alone attach a fastener to them.

Each of those pods (when fully submerged) displace about a cubic foot of water (based on the addition of 118lbs of buoyancy per the manufacturer.)

1/4-20 threads set in 5052 aluminum have a max torque spec of 6ft/lbs (that is the spec for 6061 aluminum which would be stronger than 5052 - I could not quickly find a reference for 5052). With the additional leverage of the flotation being set off from the back of the transom you could very well have enough torque from the float's buoyancy to tear out the threads. If you're going to go that route you should use a sufficient number of rivnuts along the bottom of the float to hold against the torque exerted by the boat coming off plane and loading up the float.

This is all as opposed to the shear strength of a SINGLE 3/16" closed end blind rivet (210lbs) which I still suggested you use multiple rivets to attach angle to the sides of the float resulting in a drastically stronger connection to the float. At that point you could use a pair of stainless fasteners to hold each angle to the transom and only have 4 holes per float through the transom. Here is the rivet I'm referring to: https://www.fastenal.com/products/details/0126373

Going with the rivnuts you're going to need far more perforation of your transom to achieve a fraction of the holding power.

 

[onthewater102]

I think you misunderstood my reference to angle in my 1st comment- I was referring to attaching extruded angle (such as 1"x1" american std. available from Home Depot) to the sides of the pods to allow attachment to the transom, not for adapting them to the deadrise pitch of the transom.

 

[SteveBob]

Understood on your post on the side supports although I do not see the need since I will be mounting them flush to the transom. The rivnuts are not aluminum but are actually stainless steel as will be the washers and bolts. The shear strength should be at least as strong as bolting them on from the inside of the pod which is totally acceptable per the manufacturer and many posts I have read and videos I have watched. Also as I have mentioned earlier, they are not 1/4" 20 but rather 3/8" 16. This is the bolt size the manufacturer recommended for bolting them on. I think the aluminum will rip before the rivnuts fail.

 

[onthewater102]

I did miss both the size and that they're stainless, the image you posted looked like they were aluminum.

As long as you're able to set them all without breaking the tool you should be fine, they're not prone to having the threads strip out as is the case with aluminum ones. I used stainless 5/16 rivnuts to anchor my pedestal bases to the deck framing in my boat, I'm sure my weight 2' off the base exerts far more torque on them than you're going to contend with.

 

[SteveBob]

The tool makes short work of the rivnuts. I compressed 3 of the rivnuts so far to test it out and I don't think installing 10 to 12 rivnuts will hurt it. It takes a firm pull with both hands but not enough to break the tool in my opinion. It bends the rivnuts right where they are supposed to bend. The rivnuts are designed to work with this tool or vice versa. This not a pop rivet gun, its a two handed heavy duty tool that is made for installing these nuts without jacking the threads. You can see it in one of my earlier posts.

 

[gogittum]

The OP has made it very clear that his rivnuts are steel and very strong, so I doubt there'll be a problem with the threads. I have 2 concerns about them - 1st, as I stated originally, that they have a bad habit of spinning when putting a bolt into them and 2nd that - to my knowledge - they install similar to a pop rivet, in that you push the end into a drilled hole in the aluminum pod, then pull it tight to swell the end and anchor the threads.

Pop rivets, and, I assume, rivnuts, only give a rounded bump on the inside of the pod and will pull out of aluminum fairly easily. I made a point of that when I spoke of the steel rivet's strength in shear.

In any case, OP seems to have thought it out and does have experience with his choice. It'll be interesting to see how it flies....swims..??...when done and in the water.

 

[gogittum]

I hadn't seen the later replies when I posted that last, so it's somewhat redundant.

The heavy duty pop riveter I mentioned buying is almost identical to your rivnut puller