New to me second hand boat cracking, bugger

[gazza2006au]

So i bought a second hand aluminum boat a couple of days ago took it out for a spin pretty much strait away (on our way home) and i can hear a clicking noise it seems to be coming from the horizontal transom support it looks like it has been reinforced by a previous owner i think the clicking noise is perhaps the aluminium cracking

me and my cousins went fishing yesterday and noticed the boat took on around 45 litres of water in the hull

today me and a mate went out and on returning we took on around 30 litres for 6.5 hours fishing so my mate looked under the hull while i was packing up and he noticed a small previously welded crack reappearing on the center of the weld

the tinny has been highly modified, center seat removed, full floor put in, transom beefed to the shit house

the crack on the underside of the hull isright below the front bench seat but its not from the seat

i'll wash the boat out tomorrow and post up pictures

i have a aluminium welder but instead of just gluing the cracks up i want to work out why its cracking and try figure out the transom creaking noise

boat is unknown make 4.3m it was a 3 seater open hull tinny with no floor, has only a 30hp motor

[Dan5]

Does it have a sounder fitted?............you could possibly be hearing the tranceducer clicking.

As for taking on water fill it up on the trailer mark it and just get it welded properly.

[shaungonemad]

This could be caused by a few things crap welding, poor trailer set up, and if like mine there was to much of a gap between the stringers? and the floor allowing to much movement which was stressing the weld. I was told that there are two types of alloy boats those that have cracked and those that will.

[lethal]

I hit a submerged log in my tinny 5 years ago and gave it a solid tear/crack. got it fully repaired for a couple hundred bucks. not a big deal. repair and enjoy it

[Feral]

Yeah, just weld it, and if your going to use it at night, get the nav lights fixed so they are legal.

[Noelm]

Yep, get it welded properly, it will probably crack again, but just weld it again, get a small bracket welded on the funnel to fit the lights properly, or buy some legally designed flat mount ones.

[gazza2006au]

heres the crack and some transom pictures i think the transom has two added horizontal support beams added than they lifted the motor about 40mm and welded in another add on to it plusa plate across the front of the transom to tie in both horizontal supports

the horizontal supports were tied into the sides of the boat on the outside seems strange?

[The Woo]

It's cracked under the rib. Quite common really. You'll just need to repair weld the boat occasionally - no going back now.
if you can hear the transom creaking you'll find a crack if you look hard enough.

that boat doesn't look like it needs more than a 30 either by the way.

[Spaniard_King]

Be very aware of boats that remove the centre seat as this type of boat is designed strength wise around this seat!!!! when removed you are messing with the structural integrity of the boat and there should be stiffeners should be added to compensate for the seat. Have a look at how many centre ribs a new boat has compared to that one!

[aussiebasser]

Seems to be a lot of holes drilled below the waterline in transom too. Get that crack welded up, it would be better if they could get at it from the inside to weld it, and use a heat sink on the outside, but a good alloy welder will do it right.

[Moonlighter]

Be very aware of boats that remove the centre seat as this type of boat is designed strength wise around this seat!!!! when removed you are messing with the structural integrity of the boat and there should be stiffeners should be added to compensate for the seat. Have a look at how many centre ribs a new boat has compared to that one!

100% agree with this. We have just modified a Stacer Proline that had 3 cross-thrwart seats and the guy that removed the centre seat for us was an experienced boat builder and said the same thing. He has added several extra ribs that run inside the boat and up to the gunwales, plus we had a flat floor structure welded in that, as he said, would add fore and aft strength as well as lateral strength to the hull that the seat previously provided.

That crack in your photo, running across the hull, looks very likely to me to be caused by a weakening of the hull in the fore and aft plane - in other words, the boat is bending in the middle due to the loss of strength in that plane from the seat being removed. It will just keep cracking if you dont address that issue.

I would suggest getting an experienced alloy boat builder to look at it, tell them the thwart has been removed, and get it properly strengthened, and then fix the crack.

[The Woo]

While I am hearing the thwart seat removal argument, the horizontal crack shown in the pic is well forward of the bending/flexing/cracking area seen when middle seats are removed without alternate strengthening.

I venture to say this boat has simply been to hell and back. I looks a lot like one I abused to death when my body could handle the bashing. It even had the centre thwart seat still in place.

[Noelm]

Cracks like that are pretty common in tinnies, just get it welded again...and again

[gazza2006au]

Thanks for the replies and advice guys i appreciate it, i will have to remove the motor soon and tow it down to the aluminium welder

i actually remember my cousin (6 foot tall) putting one of his legs down the front of the front seat so he could have possible stepped on the anchor causing the crack, 110kg guy but in saying that its a crack on a existing repair

about the middle seat being removed this tinny was a open tinny no floor just like the 3-3.75meter tinnies from the dealer they have no floors and basically a empty shell with the two seats, now someone has welded in a full raised flat floor with lengthwise and side way structures or like stringers it hasnt been done professionally but it has been done to a good standard

actually i'll go get pictures now

i just pulled up the floor the sections that would lift up seems there is floor bracing from side to side but no structure front to back maybe its hidden under the ply floor

u can see the rivets where the middle seat use to be

[gazza2006au]

this is the floor with the plywood down