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Mark77

Advice on old tinny

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Hi,

     I recently bought my first boat. It is an older Clark 3.66 and has a 2003 model USA made Mercury 9.9 on it. Overall in very good condition for its age.

I have noticed a couple of things from my first outing and would appreciate advice from some experienced boaties.

The boat is very light. From what I understand it was kind of like a Car Topper. I read that it weighs 57kg. The rolled sheet flexes if you push hard and I think I read that it is 1.6mm thick.

With the 9.9 it goes pretty fast. On the GPS speedo it showed 35-40km/h depending on the current.

When going along, there is a little flexing in the frame - you can see the front twist slightly when hitting small waves (it is only a river boat). I'm not to oconcerned as I imagine this is due to the light construction and fact that there probably aren't as many horizontal ribs as a heavier duty boat.

What I was a little concerned about was that just in front of the driver, there is a gap between the floorsheet and the rib. It is probably about 8mm. The hard plastic moulded strip that goes between the floor and rib is in poor shape (cracked and bit broken off) but essentially still there. The gap seems like it was not intended to be there from factory and has formed between the plastic strip and the floor. I'm thinking either it fatigued over time, perhaps overloaded or something. The issue is that when you are going along, this seems to allow quite a lot of flexing in the floor sheet. It is like the pressure of the water underneath means it is constantly rippling in and out with the water.

I'm wondering if this is something to worry about and whether the flexing might lead to cracking if left as is.

My immediate thought was to get some kind of foam/plastic/rubber stripping and use it to fill the gap. The question is what to use? It would have to be flexible but also not retain salt water or allow salt to accumulate causing corrosion. I rang a few marine shops, whitworths, plastic moulding companies etc and no one seems to know. One said use HDPE. Another suggested EDPM.

The other thing I was wondering is that the boat was in the water for about 24 hours, and when I drained the bug it had about 2L of water in it. Is this normal for an old tinny or should I be looking into this further. I was thinking about partially filling it with water to see if I could find a leak. Is this the best way?

 

Cheers,

Mark

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I can take a photo of the gap but harder to show the flexing. I'll try to take one tonight.

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Rather than fill it with water, which will push the floor out from the weight, simply put the boat in the water and look for leaks, especially around the bung and along welds.

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17 minutes ago, noelm said:

Rather than fill it with water, which will push the floor out from the weight, simply put the boat in the water and look for leaks, especially around the bung and along welds.

I had a pesky leak in my tinny. I just silicones up all around the joins on the floor.

 

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Do not fill it with water. Boats are to displace water - not hold it.......

I would expect an old boat to leak.

We have an old savage, the is known a leaky, but is a great boat.

Make sure that the inside is dry and then look where the water is entering. As mentioned, it is most likely from the bung area.....

 

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I had over a dozen pin-holes in my old 10 foot tinny. If you stood it on the transom, keel toward the sun you could see them all from the inside.

A little clean with  meths and a scourer and a dob of plasatbond... and all good.

I used a mates 14ft tinny for over 5 years... with a twig pushed into a hole in the bottom....

 

A small amount of water overnight could just be condensation?

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MY old tinnie used to have a small leak which after a day out would have 2 or 3 ltrs.

I took the floor out, washed the hull down with the Gerni and then put the boat in the water and between the kids and I we all stood on the seats and looked for the holes.

Found 3 small holes at the front and used Kneed it (2 part epoxy White & Blue) made it into a small cone and really pushed hard so it went into the hole. Did the same on the outside and for the next year not a drop of water.

The flex in floor is a concern and you need to sort that as it will crack welds after a while.

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if you use silicon use one that has neutral cure written on it thats what I got told to use.

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Thanks to everyone for the advice. I think as far as the leak goes, I'll start by putting a new bung in and put it back in the water and look really hard around for any signs.

I've attached a photo of what I mean by the gap between the floor and the rib.

IMG_20190905_184732626.jpg

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The part with the patchy paint is the plastic strip. It sags off the rib a bit and if you push it back on properly the gap is a bit bigger than shown.

Any suggestions on how to fix this?

Edited by Mark77

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Just an update on this. I filled the boat with just a little bit of water and found a clear pinhole leak. It was forming a drop about every 10 seconds in a spot that was under a rib so I would never have found it from the inside. I might get some knead it and see how it goes.

 

As far is the gap under the rib goes, I found some edpm foam strip at Bunnings. I might cut some pieces and try to squeeze it under the ribs and see if it helps. 

 

 

 

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Mark. Shame you are so far away, I could have turned the boat upside down and welded the pin hole for you.

When using the " Kneed  it " it has to be applied to a clean surface so sand around the hole ( maybe bigger than first thought ) get a small drill ( or countersunk bit ) and drill half way through the hole, not all the way so it has a countersunk formation ( this gives the compound something to grip to ) It wouldn't hurt to put a small dent in the hull, fill the hole ( and dent ) with the compound and leave a small amount spread over the hull where the hole was. It wont matter that there is some build up but don't make it a mountain just a slight raised amount.

Another tip when using Kneed it is to have a container with water in it and wet your fingers while kneading the compound and pushing it into and smoothing out the compound.

Frank

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13 hours ago, Mark77 said:

Just an update on this. I filled the boat with just a little bit of water and found a clear pinhole leak. It was forming a drop about every 10 seconds in a spot that was under a rib so I would never have found it from the inside. I might get some knead it and see how it goes.

 

As far is the gap under the rib goes, I found some edpm foam strip at Bunnings. I might cut some pieces and try to squeeze it under the ribs and see if it helps. 

 

 

 

The foam may not be a good idea. You don't want anything which will hold water up against the hull as it will cause corrosion.

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6 hours ago, frankS said:

Mark. Shame you are so far away, I could have turned the boat upside down and welded the pin hole for you.

When using the " Kneed  it " it has to be applied to a clean surface so sand around the hole ( maybe bigger than first thought ) get a small drill ( or countersunk bit ) and drill half way through the hole, not all the way so it has a countersunk formation ( this gives the compound something to grip to ) It wouldn't hurt to put a small dent in the hull, fill the hole ( and dent ) with the compound and leave a small amount spread over the hull where the hole was. It wont matter that there is some build up but don't make it a mountain just a slight raised amount.

Another tip when using Kneed it is to have a container with water in it and wet your fingers while kneading the compound and pushing it into and smoothing out the compound. 

Frank

Thanks Frank. Much appreciated.

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3 hours ago, kingfishbig said:

The foam may not be a good idea. You don't want anything which will hold water up against the hull as it will cause corrosion. 

I am concerned about this but I thought these type of "closed cell" foams are not supposed to absorb water. I guess anything put there will have the potential to hold some water (and salt) in the area. The only other option I can see would be to use some kind of hard plastic like the strip that is under the ribs (like cutting board or something) but it wont be very flexible and might have to be glued in to keep it in place.

Edited by Mark77

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21 minutes ago, Mark77 said:

I am concerned about this but I thought these type of "closed cell" foams are not supposed to absorb water. I guess anything put there will have the potential to hold some water (and salt) in the area. The only other option I can see would be to use some kind of hard plastic like the strip that is under the ribs (like cutting board or something) but it wont be very flexible and might have to be glued in to keep it in place.

I think a hard plastic would be a better idea.

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Years back I had a tinny with a leak under a frame, near the keel line. I drilled it out and inserted a blind aluminum pop rivet. Packed it with 2 part epoxy. Never leaked again

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