Leaks in pontoon behind lifting strakes

I need some advice from someone that knows about aluminum structure and welding. I have determined without a doubt that I have some leaks in my pontoons behind the lifting strakes. When the lifting strakes were added the welding company skip welded the strakes about 2-3 inches long every 2-3 feet rather than welding them solid. I pressurized the toon to about 1 PSI and used a short piece of garden hose to listen with and I can hear air blowing in several places behind the strakes.

It?s easy to live life in the rear view mirror and say ?if I would have only ? then ?? But my situation at this point is there are pin holes either in the strake welds or in the joints between tube sections that are not accessible. I?m looking for input on what to do.

I?ve seen strakes on some new boats that are welded continuously down the entire strake making them sealed air tight. They could always put a drain plug in the rear. Is this long of a weld feasible? If so, we use about 1 psi of nitrogen flowing through copper while brazing refrigerant lines to reduce oxidation internally. The other end of the copper is open. Would this help keep the foam inside from burning?

Other ideas??

Re: Leaks in pontoon behind lifting strakes

MaPaHa said:

I need some advice from someone that knows about aluminum structure and welding. I have determined without a doubt that I have some leaks in my pontoons behind the lifting strakes. When the lifting strakes were added the welding company skip welded the strakes about 2-3 inches long every 2-3 feet rather than welding them solid. I pressurized the toon to about 1 PSI and used a short piece of garden hose to listen with and I can hear air blowing in several places behind the strakes.

It?s easy to live life in the rear view mirror and say ?if I would have only ? then ?? But my situation at this point is there are pin holes either in the strake welds or in the joints between tube sections that are not accessible. I?m looking for input on what to do.

I?ve seen strakes on some new boats that are welded continuously down the entire strake making them sealed air tight. They could always put a drain plug in the rear. Is this long of a weld feasible? If so, we use about 1 psi of nitrogen flowing through copper while brazing refrigerant lines to reduce oxidation internally. The other end of the copper is open. Would this help keep the foam inside from burning?

Other ideas??

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I believe most lifting strakes are skip welded. When you air tested them did you try using soapy water to see exactly where they are leaking?

Re: Leaks in pontoon behind lifting strakes

Yeah most of the strakes that I have seen are skip welded with the exception of the odd one which is fully welded. If they are leaking under the strakes the way I see it is you have only 2 options, Weld the strakes up completely so that they are air tight, or remove the strake so you can fix the leak. My pontoons had leaks at the front and at the back where the upright mounts are welded to the pontoon. It was right on the weld where the mounts had flexed and cracked the weld. I found out exactly where the leak was and ground away some of the mount and weld so that I could get at it with a welder and welded them and the mount back up. You could do the same thing. Do as lakegeorge suggested and use a water/soap solution to pinpoint the exact leak points. I mixed water with dish soap (60/40) and put it in a spray bottle and spray every spot of every weld on the whole pontoon and mark the leaks with a marker. When you find a leak mark it and keep going as there may be more that one leak. Pay close attention to the where the mounts are welded to the pontoon. If your strakes are only stitch welded they should the open at the back so look in there with a flash light to see if you can see bubbles. I have been through all this last year. With the soap solution if there is an air leak you will definatly see it.
As far as purging with nitrogen to keep the foam on the inside from burning, if they are round pontoons I highly doubt that there is foam inside of them. The only pontoons that I know of that had foam in them was the older "U" shaped ones. What kind and year of boat is it? Good luck.

Re: Leaks in pontoon behind lifting strakes

MaPaHA, did you have someone weld those strakes on for you,or did you buy it that way? They should of pressure tested it after they were done. Let us know what you find.

Re: Leaks in pontoon behind lifting strakes

If he dosen't chime in soon, you might try sending a PM to "5150ABF". He's an expert in this field. Good luck !!!

Re: Leaks in pontoon behind lifting strakes

It’s an Aloha boat with round 23 inch toons about an 83 model. I just ran an inspection scope through the rear drain (ouch) and it’s definitely got foam in it. The foam stops flat about 3 inches from the bottom leaving a half moon shape at the bottom for air and/or water. I saw where the first weld was a couple of feet up and it didn’t hurt the foam.

Yes I had the strakes added last year. I bought them from Bills boat stuff in southern Missouri and they were full length anodized aluminum. I placed them where I wanted and strapped them on and had a local welder weld them on. None of the outer welds leak where you can see them but I have a feeling there were a few blowouts on the inside. I did what y’all said with the water and soap and I could see some bubbles running out of the seam where it wasn’t welded but to get to it would take grinding the weld off and a bit extra and then re-filling it back with a weld. I fairly accurate in saying there are several welds leaking inside and maybe a joint where one 5 foot section joins to the next. The toons were tight before the strakes were added but they had been welded on before. I thought the strakes would help strengthen up the old toons as well as add performance.

The toons started picking up water immediately after the strakes were added and the welder said to bring it back but I really don’t know how he’s going to fix them. I would rather come up options first. The toons had a factory vent into a cross member so you could not pressurize them but the welder said a lot of toons were like that so they crank up the air volume so they can get a PSI or two even with the open vent for testing. That’s what they did last year and there were no outer leaks and I’m sure the shop was noisy so they couldn’t hear the inner ones. This year we drilled the square vent tube and pumped it full of silicone so now they can be pressurized and he welded me a couple of new vents that have pipe threads in them. Again, you can spray all the welds down that you can see and only one leak is evident but I can hear air leaking inside the strakes in several places with my “garden hose listening tool”. And, it doesn’t hold pressure.

Last week my wife and I went to the Arkansas River about 10 minutes away in downtown Little Rock and ran it up river about two miles and back to log the speed and RPM before I change motors and put it back on the trailer. When I got back home there was a large Coffey can of water in each toon. A weekend at the lake who knows.

On a side note, I ran a ? hose from the new ports the welder installed to inside my storage compartment so I can hook up a water toy air pump and pump air into them on the lake if I need to. The pump will produce ? PSI which is 14 inches of water column. The boat doesn’t float that deep so it will be positive pressure even at the bottom of the toon. The new fitting is on the front and it takes less than a minute to reach 14” water column at the back drain. Don’t want to depend on this but in an emergency it would get me back to the ramp.

How much pressure do you pressure test with? I got a bit scared at 2 PSIG.

What do y’all think? Weld solid, cut them off and start over with a bunch of cobbled up places, or grind down and dig out the bad welds and try to fill them back in and that’s if the joints don’t leak which would have to have a gap cut out to get to them?

Thanks

Re: Leaks in pontoon behind lifting strakes

Honestly you would be better off to buy 2 brand new toons with strakes on them.

Re: Leaks in pontoon behind lifting strakes

MH Hawker said:

Honestly you would be better off to buy 2 brand new toons with strakes on them.

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Do you work at an auto Dealership?

Give the welder another shot at fixing it.

Re: Leaks in pontoon behind lifting strakes

Welding them solid doesn't seem like the answer to me. Then you would have 80' of weld to keep air tight. If it was mine and there were only a few stitch welds leaking I'd cut small pieces out of the strake,only on the side of the leak. Carefully grind enough of the weld away to break the piece loose. Clean the weld off the tube, patch the hole, test the tube, then weld the cutout piece back in. You can grind,sand,and buff the welds smooth on the surface of the strake if you want. It doesn't have to be air tight. Patching the hole would be the hard part,and probably would be better if done with a tig.

Re: Leaks in pontoon behind lifting strakes

A competent welder and a drill are called for here, you need to pin point the leak then drill a few small hole around it on the weld and reweld it, air check and when the leak is dead refill the hole.

If you do It right you can hardly tell you were ever there.

Grinding the weld out would work but you have to be super careful, the tubes are only .080 so it really easy to go a bit to far then you have a slit and not a pin hole.

As to welding all the way around, YIKES, that would take a really long time and really wouldn't do anything for you.

My guess would be whoever you had weld on the chine sisn't remove the plug before they welded them and the air pressure built up and popped a small hoe in one of the welds.

Judging by the pics the guy you had do it the first time is still pretty new to welding aluminum, those are pretty lumpy welds so maybe don't take it back to him.

When you do find a guy to do it I would be glad to give him any tips he might need, PM me.

I have been building pontoons for 26 years and currently supervise the tube line at Bennington so I have done this exact thing numerous times.

Re: Leaks in pontoon behind lifting strakes

5150abf said:

Judging by the pics the guy you had do it the first time is still pretty new to welding aluminum, those are pretty lumpy welds so maybe don't take it back to him.

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Sorry 5150abf, that photo are my bumpy welds,and I don't weld aluminum for a living. I staid fairly cold on the temps,as I was scared of that mig on .080 Not even sure if mine are that thick. Tried to keep most of the heat on the strake itself.

you need to pin point the leak then drill a few small hole around it on the weld and reweld it, air check and when the leak is dead refill the hole.

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If you don't mind explain that a little in case I run into that one. If he's leaking inside the strake how do you pinpoint it? If he blew through then filled his hole he may still have a hole on the back side of his weld under the strake.

Re: Leaks in pontoon behind lifting strakes

Didn't say they were bad just not real experienced, it take years and hundreds of hour of welding to get really good.

You have the basics down just time now, the weld dropping is a wives tale by the way, you can do it but you have to really try.

My 2 biggest rookie tips are watch for the metal to go shiny, as you strike your arc the metal will turn chalky grey, sit on it for a second and it will go shiney, now it is ready to add rod, everyone wants to start adding rod as soon as they have an arc and you have to wait for the metal to melt the other is , play Pac Man, if you watch a weld it is just like playing pac man, when he opens his mouth feed him.

You find the leak with soap and water and a little air, air the tube and spray it and you should be able to see which end it is leaking on then drill just below the top of the weld and just till you get through the weld, do 3-4 in a row then hit it with your welder to get the metal out of the way and respray, repeat until you find the actual leak.

Repair the leak, recheck when it doesn't leak you fill it in again.

Very important to let all the air out of the tube before you start welding or the air will blow out the hole and you will never ever get it to fill, of coarse the worst thing for a weld is oxygen also as I sad the tube needs to be vented before you do any welding on it.

The air inside the tube heats and expands and at some point will blow out the weld, a lot of times this appears as an inclusion in the weld lie you are welding over something but it will never ever fill, vent the tube and you are good.

Re: Leaks in pontoon behind lifting strakes

Ah, I done mine with a spool gun on a mig,not a tig. And,I can make a weld fall away on .090-.080 in a heartbeat with it.

I've said it before and I'll say it again. I wouldn't recommend a spoolgun for this,but it worked for me. If MaPaHa's was tigged I'd lay money on your theory. I've had the non-vented problem happen welding stainless plumbing.

Re: Leaks in pontoon behind lifting strakes

Thanks for the input.

MH Hawker,
As far as big money goes, I’m done with this boat. It’s about as far as I can go with what I have to work with but I plan on using it for 2-5 more years. My next build will be what you say and I’m starting with three new tubes. I’m going to take the approach BrianMc took and build it the way I want with all the features for our use. Cruising, tubing, skiing, camping on it, top cover, fishing and 40mph. If there’s a way, I need to fix this one but it has to be safe and dependable.

5150abf, BrianMc
Thanks for the input. Y’all have convinced me not to have them welded solid which was the way I was leaning. I don’t know anything about aluminum welding but I’ve built several steel trailers, and all kinds of stick and mig welding over the years. This was done with a spool gun and I’m not sure about the venting.

The challenge here is the welds that are leaking are located behind the strakes and you cannot hear or see a direct indication of the leak with soap/water. So some serious digging will have to be done around the suspected area to get to the failure and then built back up as they come out. In fact it’s hard to determine which welds are leaking other than a general area where you can hear air coming out. Some cutting will have to be done to get to the joints if they are leaking. It sounds like the plan should be; find the weld areas that appear to be leaking and address those issues on an individual basis.

If it gets down to 50% or more of the welds we may just take them back off and start over. I think I understand about the drill holes and the significance of doing that. I remember years ago welding up a cast iron engine block with Nichol-arc rod where I drilled at the end of the crack to relieve stress and filled the hole last. This may not be the same exactly but maybe the concept is similar. I’ll pass that on to the welder.

Thanks so much for the input. If y’all think of any other way to get behind the strakes please throw it out there.

Re: Leaks in pontoon behind lifting strakes

MaPaHa, do your strakes look like this? Believe I bought mine from the same guy.




If so there won't be any welds on the inside. Since yours were welded with a spool gun I'm afraid he may have blown through several times,stopped to fill the holes,and moved on to the next bead. My guess is the filler bead bridged over the hole to the strake's edge,rather than actually filling the hole. It'll look good on the outside,but part of the hole is still under the strake and why it's leaking to the inside like that.

Reason I know this is out of all the welds on my strakes I only blew through once with the spool gun. It was my last weld and it happened right at the corner of the nose cone were I hesitated for a split second to turn the corner. I knew better,as on the other side I stopped then started the other direction after it cooled. When I went to fill it I had to be very careful because the hole was right at the strake's edge. No way to bridge across the hole,as the strake covered the inside edge of the hole. I kept spot welding the inside edge of the hole to the strake until I though it was airtight,then bridged over the hole to that weld. I got lucky and didn't have to cut anything away. Hope that made sense?

Drilling the holes won't work the same with a spool gun. It'll take a tig to do that.

Re: Leaks in pontoon behind lifting strakes

Go find yourself a really good welder. Because someone works in a welding shop doesn't mean they're qualified to weld aluminum.

Follow 5150ABF's advice. He's a professional in the tube shop of the top pontoon manufacturer, and he knows what he's talking about.

I always thought the best aluminum welds come from TIG welding.

If someone's considering adding lifting strakes to their pontoon boat, the boat should have 90 hp+, and preferably more horses than that. But they really need to be added to a 25" hull, and one that's preferably a later model boat. There's no use throwing good money after bad money.

Re: Leaks in pontoon behind lifting strakes

BrianMc said:

Welding them solid doesn't seem like the answer to me. Then you would have 80' of weld to keep air tight. If it was mine and there were only a few stitch welds leaking I'd cut small pieces out of the strake,only on the side of the leak. Carefully grind enough of the weld away to break the piece loose. Clean the weld off the tube, patch the hole, test the tube, then weld the cutout piece back in. You can grind,sand,and buff the welds smooth on the surface of the strake if you want. It doesn't have to be air tight. Patching the hole would be the hard part,and probably would be better if done with a tig.

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He used a MIG welder on alum that is to thin that is a big no no in the alum welding field.

You have pin holes on most the stop points on your stitch welds.

Your best bet at this point if find a good TIG welder and have them go back over the welds and smother them and make sure there are no holes. Do this with the vent open so that when head builds up and so does the pressure you dont just blow the weld out.

When I add the strakes on mine I started with a MIG spool gun and did like the results I was getting and swithed to TIG. All the mig welds had leaks on them. They were very small but they still leaked.

Re: Leaks in pontoon behind lifting strakes

BrianMc
Yea he’s the same guy. He’s a good guy, very helpful and likes what he does. When they fab’d my center toon to spec his welder did a great job. No problems. I went back to get the strakes a year and a half later for the outer toons.
There’s no doubt you understand what and where my problem is and what it’s going to take to fix it. What happened to you once happened about a dozen times on mine exactly the way you said it. I wasn’t there and watching but you’ve got it pegged.

If it was as simple as pressurizing the toon, spraying it down, finding the leak and fixing it, I wouldn’t be writing all this and asking for someone to take the time and effort to answer.

Bamaman1, TurboM700
Thanks for the input. Reading you’re comments help reinforce what should be done to fix it and what kind of machine to use. I’m not sure what kind of welder it was other than a spool gun is what they called it. I’m definitely going to follow 5150abf’s advice. I hope there’s a way to cut enough away without butchering the strakes to get to a point where it can be drilled, fix the toon first, pressure test it and then re-weld the strake welds. This welder has done a good job for me on several occasions and they do a fair amount of pontoon work but I think they usually TIG weld most of it. I’m sure they can fix it right but it’s probably not going to be the same guy. When they put in my air vents the welds look perfect and the other work they did on the cross members a few years back looks good also.

I agree the lifting strakes won’t do much good on low hp boats. There’s a delicate balance between lift and drag that’s hard to understand. Mine’s a 140 going to a 150 in the next few weeks when this is fixed. I’ve already pulled the 140 motor off and maybe that will help them lift and block it to get to the work area better.

Would anyone recommend cutting off a few feet of strake from the back or leaving them full length? Now’s my chance.

Thanks again to everyone who took the time to respond. As I mentioned, I’ve got a lot of experience in steel welding but absolutely none in welding aluminum. I’ll post back on how it goes.

Re: Leaks in pontoon behind lifting strakes

edit: I'll be nice.

Re: Leaks in pontoon behind lifting strakes

OK, I'll say it one more time. Yes I agree the tig is the way to go here. My tig doesn't work for aluminum, stainless yes. Nor do I have access to one. The nearest "professional" shop is 60 miles away,and I've already had to fix their aluminum welds for others.

I done this to MY toon,and it worked. Despite what was said the welds in that photo do not have pin holes. They've been holding air for a year now. I never advised anyone to follow suite, just here to help someone that had theirs migged.