Tohatsu 3.5 2 stroke

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brians

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The plastic fuel tank in my engine has started to leak but cannot see exactly where at the moment. Think it may be at the welded join between the two halves. Has anyone else experienced this problem? Can it be repaired or does it mean a new tank?
 
HSE will shoot me down in flames for this. I had a leak on my lawnmower fuel tank which turned out to be around the fuel take off. I drained the tank and flushed it with alcohol to remove any oils and left it to dry for a few days.
I then welded up the joint with a hot-melt glue gun.
It's been leak free a couple of seasons now.
 
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The tank on mine looks like that slightly greasy feeling plastic (polyethylene?) that#'s almost impossible to glue, but can be welded quite successfully with a soldering iron.

If it was me & I could identify the location f the leak, I'd have a go with an electric soldering iron - not a flame heated one for reasons which I hope are obvious. Empty the tank and fill completely with water then drain first, just in case.

You take this suggestion at your own risk - they're your eyebrows :eek:
 
I had one that leaked around the fuel cap, so it only showed when the engine was laid down in the boot of the car. Replaced the fuel cap etc but it still leaked so I guess it was in the tank join in the area of the screwthread. The soldering iron idea sounds good, I have mended water butts like that.
I never did fix it, and eventually to engine was sold - not because of the leak BTW, a fine engine.
 
I have the Force 3 badged version of this engine and mine leaked from a split in the plastic in the filler. The crack was at the thread root and ran round the thread for 1/3 of a turn. I tried the soldering iron solution but had no faith in that repair. As I carried the engine to and from the boat in the car, a petrol leak could not be tolerated and I renewed the tank. Cost a small fortune!
 
If the tank is polyethylene or polypropylene epoxy is not likely to stick.

"welding" or bodging with a soldering iron are probably the only two options.
but
Hot melt glue gun sounds an interesting idea provided you can find a suitable "glue" stick and gun but if you have to buy a gun it might cost more than a new tank .. with no guarantee of success
 
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Stemar said:
The tank on mine looks like that slightly greasy feeling plastic (polyethylene?) that#'s almost impossible to glue, but can be welded quite successfully with a soldering iron.

If it was me & I could identify the location f the leak, I'd have a go with an electric soldering iron - not a flame heated one for reasons which I hope are obvious. Empty the tank and fill completely with water then drain first, just in case.

You take this suggestion at your own risk - they're your eyebrows :eek:
Click to expand...
10 years on and its still a useful post. For any future searchers let me add I've just successfully repaired mine. Seemed like it might be a design flaw as its not been damaged or much used. The tank was still white not even yellowed from having oily petrol in it which happens pretty quickly when its used. So I didn't want to buy a new one and find it happens again, better to fix it with a new welded seal around the outer edge of it.

Worth saying that it will ruin the soldering iron tip. I guessed as much, couldn't get any Weller tips locally so bought a cheap new iron for the job. I tried cleaning and re-tinning with special tip tinner and it doesn't work. Could get a new tip but they cost as much as the whole iron so I'll keep this just for similar jobs.

Its a 60w iron and I still had to wait a long time to get to a temperature that would melt the tank. The plastic of the threaded part melts at a lower temp than the tank so wait until its hot enough to melt the tank before starting. I found with the tip parallel to the flat of the tank lightly scrapping a bit of the tank towards the join and then bringing a bit down from the lip of the threaded part next to the join to mix with it worked well but watch the heat which builds up in the material. I needed to blow it cool after each part I did as the plastic seemed to keep changing even after I'd removed the heat, went transparent until it cooled. So just go along a small section at a time and keep blowing it cool for a few seconds after each bit. I used a vacuum tester to check and its fixed for now at least. This plastic seems to really like to be welded so it doesn't feel like a bodge at all.
 
VicS said:
If the tank is polyethylene or polypropylene epoxy is not likely to stick.

"welding" or bodging with a soldering iron are probably the only two options.
but
Hot melt glue gun sounds an interesting idea provided you can find a suitable "glue" stick and gun but if you have to buy a gun it might cost more than a new tank .. with no guarantee of success
Click to expand...
I have repaired lots of plastic stuff with epoxy and glass. I would roughen the whole tank and wrap it in epoxy and glass. Thickened epoxy at the crack with a couple of layers of glass over the top should work. I did a similar temporary fix on a 10 litre water container a few years ago. Its still going strong.
 
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