Why is my outboard leaking fuel

stuartwineberg

stuartwineberg

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My trusty Tohatsu 3.5 lives in the lazarette and never leaks a drop. It has been stood upright empty all winter and now, with about 1 litre of fuel in it, it leaks all over the place when tilted towards the end with the controls. it runs fine by the way. Before I take it to bits - can the forum advise me of likely issues (?something like a float is stuck??)
 
I own a Mariner 3.3 and had a fuel leak last year, outboard is about 5 years old. Eventually traced leak to the rubber fuel hose from the fuel tank.
Renewed hose and no more leaks.
 
gregcope said:
As you say stuck float would be my guess.
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If it is flooding that badly due to a stuck float or non seating needle valve it would not likely to be running fine

My guess is that the fuel tap is not closing... it can't be closing if fuel continues to leak!.

If the tap is still open then there is a good chance that when the engine is tilted forward fuel will leak as the float will only be effective if it is near to upright.

I would check the fuel tap before messing with the carb!
 
I have a johnson 3.5 which may or may not be the same carb. I've had the same problem, loads of crud in the float bowl of the carb has caused the same symptoms.
 
homa said:
I own a Mariner 3.3 and had a fuel leak last year, outboard is about 5 years old. Eventually traced leak to the rubber fuel hose from the fuel tank.
Renewed hose and no more leaks.
Click to expand...

My mariner 4 had the same leak.

Two cable ties around the ends of the aforementioned hose stopped the leak.

When nice and fresh, that little hose just grips and seals where it plugs on. But when it gets old and tired it no longer seals very well.

I probably should replace mine rather than rely on the cable ties to seal it.
 
Update but rip off I think

Just to let the nice people who bothered to suggest what might be the problem know how it panned out. In the end it turns out that fuel is pi**ing out from the tank cap when the motor is leaned over with a decent amount of fuel in it. it wasn't obvious because capillary action was taking the fuel under the housing and leaking it out near the carb. The cap is quite complex - it has the main hard plastic body, an air valve which opens and closes on a threaded brass rod and a bell shaped inner rubber seal with a foam pad inside. There are no leaks or tears but there is a clear indentation of the tank rim in the seal suggesting that even when I screw the top up tight it isn't sealing.

The rip off bit is that you can't just buy the seal and a new tank cap is £20. I thought of trying to find a fibre washer to put in the cap but not sure what will resist the petrol. Any thoughts before I head off to the swindlery?

Thanks all
 
stuartwineberg said:
Just to let the nice people who bothered to suggest what might be the problem know how it panned out. In the end it turns out that fuel is pi**ing out from the tank cap when the motor is leaned over with a decent amount of fuel in it. it wasn't obvious because capillary action was taking the fuel under the housing and leaking it out near the carb. The cap is quite complex - it has the main hard plastic body, an air valve which opens and closes on a threaded brass rod and a bell shaped inner rubber seal with a foam pad inside. There are no leaks or tears but there is a clear indentation of the tank rim in the seal suggesting that even when I screw the top up tight it isn't sealing.

The rip off bit is that you can't just buy the seal and a new tank cap is £20. I thought of trying to find a fibre washer to put in the cap but not sure what will resist the petrol. Any thoughts before I head off to the swindlery?

Thanks all
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Is it not part number 309 70021-3 ?

It should be between £5 and £6 !
 
Thanks Vic - yes I noted that in the parts manual but the asterisk means "kit part" and the various online shops are only listing the entire cap. The local dealer is opposite our marina so I'll give them a call tomorrow but thanks again for looking up the reference

VicS said:
Is it not part number 309 70021-3 ?

It should be between £5 and £6 !
Click to expand...
 
umm, Lakey, your new aviator...

The pink parts I dimly recognise, but the black and white looks like a giant platypus bill.


Do we need Brian Sewell to explain it as protest art against being without a Project ?
 
and a quick call to Ribshop on Eastlands marina quoting the part number gets me a new one for a fiver as you say. Full marks to them BTW - wasn't in stock but they would get me one in 24 hours - picking it up tomorrow - thanks Vic

VicS said:
Is it not part number 309 70021-3 ?

It should be between £5 and £6 !
Click to expand...
 
Just fixed my leak on a Honda 2hp(watercooled leg type) bought a carb. seal kit, renewed seal in tap; still leaked from screw that holds float chamber bowl on so stripped carb, cleaned up rusty bowl, new gasket and fibre washer - not leaking but the exhaust has blown a hole in the top of the leg where the exhaust pipe joins it.......... Anybody got a spare leg?...........
 
An old thread I know, but I have the same issue with my mariner 3.3hp whereby the cap leaks if tilted too far, I just need the rubber insert, does anyone know a source or part number? I don't really want to buy the plastic cap for £35 just for the rubber insert.
 
Scubadoo said:
An old thread I know, but I have the same issue with my mariner 3.3hp whereby the cap leaks if tilted too far, I just need the rubber insert, does anyone know a source or part number? I don't really want to buy the plastic cap for £35 just for the rubber insert.
Click to expand...
It is listed as a separate part but is "unavailable"
 
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