Fuel cock on Mariner 4HP 2 stroke

[Max Campbell]

1980's Mariner / Yamaha SEO engine with drippy petcock.

It's taken me quite a while to disassemble the fuel cock, rod, knob, etc,, but I have now exposed the leaky rubber seal in the middle of the petcock. I have access to a whole new, unleaky, petcock, but I can't get the old one off the petrol tank. If I undo the captive brass 17mm nut until it's binding on the aluminium of the petcock, it's still looks as though it's engaged with the thread, and it's solid as a rock. It may just need a sharp tap, but it looks very insubstantial for that.

I could re-use the rubber seal out of the new petcock, I suppose.

Any experience / advice welcomed.
TIA

 

[VicS]

This type ? https://cdn.boats.net/cdn-cgi/image/width=768,quality=75/MTA/po/4/MTM0NDUxNA-426380aa.jpg

Looks as though it should unscrew from the tank once the brass nut is slackened.

 

[Max Campbell]

This type ? https://cdn.boats.net/cdn-cgi/image/width=768,quality=75/MTA/po/4/MTM0NDUxNA-426380aa.jpg

Looks as though it should unscrew from the tank once the brass nut is slackened.

Yes, that looks like it - so you think that's threaded into the tank? that would explain it...

 

[Max Campbell]

Derr.. I get it now - I haven't got the replacement cock to hand, and had thought the thread was part of the tank ... thanks for the help.

 

[VicS]

Another picture of the same thing ....... https://cdn.boats.net/cdn-cgi/image/width=768,quality=75/MTA/po/8/MTM0NDQwOQ-8f1c4227.jpg

isnt the new one obviously a threaded fitting?

Take care not to damage the tank as now NLA