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-   -   How to weld/glue/fix cracked outboard engine plastic fuel tank? (http://www.cruisersforum.com/forums/f117/how-to-weld-glue-fix-cracked-outboard-engine-plastic-fuel-tank-134034.html)

ErikFinn 04-10-2014 02:07

How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
I bought a used dinghy with a 5 year old 5HP Mercury 2-stroke outboard. There is a 1 cm (1/3 inch) crack at the fuel hose connection in the bottom causing the tank to leak from there. I don't know the full name of the material, but its the original plastic fuel tank. New one sells for around Malaysian Ringgit 500 (includes cap) or about 150 USD, which I think is a bit steep.
So my question is: is there an easy way to fix this? Some special glue/putty or welding maybe?

Cheers,
Erik

Emmalina 04-10-2014 02:41

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
Go see the Yamaha man behind KFC in Kuah sure he will have something for a lot less.. Or even Farid at the mecury place :thumb:

ErikFinn 04-10-2014 02:55

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
Quote:

Originally Posted by Emmalina (Post 1645013)
Go see the Yamaha man behind KFC in Kuah sure he will have something for a lot less.. Or even Farid at the mecury place :thumb:

Thanks Emmalina, "Farid at the Mercury place" is also in Kuah, Langkawi, right? :whistling:

I'm in Penang at the moment.

rwidman 04-10-2014 14:16

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
Quote:

Originally Posted by ErikFinn (Post 1645007)
I bought a used dinghy with a 5 year old 5HP Mercury 2-stroke outboard. There is a 1 cm (1/3 inch) crack at the fuel hose connection in the bottom causing the tank to leak from there. I don't know the full name of the material, but its the original plastic fuel tank. New one sells for around Malaysian Ringgit 500 (includes cap) or about 150 USD, which I think is a bit steep.
So my question is: is there an easy way to fix this? Some special glue/putty or welding maybe?

Cheers,
Erik

I don't believe there is an effective DIY way to fix a cracked plastic fuel tank.

You shouldn't need a Mercury branded fuel tank, just one with the correct fittings or one you can install your fittings on.

You might be able to find a used tank from a motor that no longer works.

nimblemotors 04-10-2014 14:27

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
What kind of plastic is it? That makes all the difference.
If it is HDPE or LDPE, you can 'weld' the cracks to seal them up.

MBWhite 04-10-2014 14:32

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
The problem with fixing plastic tanks is the plastic with expand and contract a lot differently than the adhesive and it will separate eventually unless reinforced. If you can reach inside you can fabricate a metal plate or just use a bolt and a "fender washer". Epoxy one washer to the bolt and figure the placement on the outside and drill a hole for it. Glue a piece of stiff wire to the head of the bolt so you can feed it into the hole from the fuel filler neck. Now clean the plastic tank area with plastic pipe primer used for gluing PVC or ABS plumbing pipe together, clean on both inside and outside. Now mix some fuel proof epoxy and coat the washer/bolt combo and using the wire glued to the head feed the bolt through the hole. When it is through the hole coat the outside of the tank and the washer too, then put a nut on the bolt and tighten it all together. Once the nut is on the bolt and getting snugged down, you might need to grip the bolt with a pair of pliers while you use the wrench to finish tightening. The next day, yank off the epoxied wire and you're done.

FilBrown 05-10-2014 08:34

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
Have a look on EBay there's loads of second hand parts from defunct engines.
I've had some success in fixing cracked plastic parts using a soldering iron with a blade attachment. If it's the right kind of plastic I've found that you can carefully soften the surrounding area and pull some of the plastic into the gap.
You can also sometimes take excess plastic from flanges or struts moulded elsewhere on the part although don't take too much.
I also use epoxy to cover the area I've worked on to help strengthen it.
There's a bit of a knack to it getting the irons temperature right and practice on similar material would be recommended.

:banghead:

Sun and Moon 05-10-2014 09:25

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
Nimblemotors has it right. If it is HDPE, which I think it is, no glue will bond, including epoxy. PVC products won't work either. You must weld. You can do this yourself, although getting the temperature right is difficult. Too hot and it will melt or burn the tank, too cool and the plastic won't bond. When I've done this the plastic turns transluscent when the temperature is right. The plastic can also catch fire - not necessarily a problem, I just blow it out - but be prepared for that. Practice on some junk first.

Dustymc 05-10-2014 11:03

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
I've had great luck with 5200 - I've got a badly-cracked tank with a ~5-year-old patch holding up fine.

Cheechako 05-10-2014 11:08

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
This is the tank mounted inside the engine cowl right?

ErikFinn 05-10-2014 18:38

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
Quote:

Originally Posted by Cheechako (Post 1646235)
This is the tank mounted inside the engine cowl right?

yup, the internal fuel tank, white thick hard plastic.

ErikFinn 05-10-2014 18:40

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
Quote:

Originally Posted by nimblemotors (Post 1645508)
What kind of plastic is it? That makes all the difference.
If it is HDPE or LDPE, you can 'weld' the cracks to seal them up.

Thanks but I have no idea what kind.. Would it be stamped on the tank somewhere possibly?

ErikFinn 05-10-2014 18:44

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
Quote:

Originally Posted by Sun and Moon (Post 1646134)
Nimblemotors has it right. If it is HDPE, which I think it is, no glue will bond, including epoxy. PVC products won't work either. You must weld. You can do this yourself, although getting the temperature right is difficult. Too hot and it will melt or burn the tank, too cool and the plastic won't bond. When I've done this the plastic turns transluscent when the temperature is right. The plastic can also catch fire - not necessarily a problem, I just blow it out - but be prepared for that. Practice on some junk first.

Would a soldering iron be appropriate for the job?

ErikFinn 05-10-2014 18:50

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
Quote:

Originally Posted by FilBrown (Post 1646089)
Have a look on EBay there's loads of second hand parts from defunct engines.
I've had some success in fixing cracked plastic parts using a soldering iron with a blade attachment. If it's the right kind of plastic I've found that you can carefully soften the surrounding area and pull some of the plastic into the gap.
You can also sometimes take excess plastic from flanges or struts moulded elsewhere on the part although don't take too much.
I also use epoxy to cover the area I've worked on to help strengthen it.
There's a bit of a knack to it getting the irons temperature right and practice on similar material would be recommended.

:banghead:

oh there we go hehe, I should have read this one before asking the one above re soldering iron (maybe another cup of coffee would help also :D )

But can you describe the "blade attachment" to me please? You mean instead of the normal "tip" you use some kind of a modified spade or similar shape tip?

FilBrown 05-10-2014 20:41

Re: How to weld/glue/fix cracked outboard engine plastic fuel tank?
 
I use a small hot knife blade on a gas powered soldering iron.
The blade is only about 3cm long and doesn't have a sharpened edge.
I also use it for cutting & sealing synthetic ropes.

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