Fuel flow issue - Tank needs to be higher than outboard to start initially??

[BaitThrower]

Hey all,

Just trying to work out an issue with an old Mariner 15hp carburetted outboard I have sitting here...

Basically it seems to be starved for fuel and wont start, however if I place the gas tank slightly higher than the outboard, the fuel seems to flow and she starts no problem... After this I can put the tank on the boat floor and she feeds fuel no problem... Just the initial start seems to be the problem. Thought maybe primer bulb not sucking up fuel but I tried a known, good tank with air tight bulb and fittings and it did the same... i.e. had to have tank higher than outboard initially to get fuel flowing...

Fuel seems to be getting to fuel filter as I can see it sucking it up... but after that I am not sure.

Any ideas?

[finga]

Check the primer bulb.
it could be crook.

[BaitThrower]

Check the primer bulb.
it could be crook.

Hi Finga,

I tried two different tanks each with their own primer bulbs, the second works fine on my other outboard so its not the primer bulb!

EDIT:

Well actually, let me correct that and add more info... I cannot get either primer bulb to go semi-hard when pumping it when hooked up the motor, however, if I connect the same tank and lines to my other outboard, it sucks the fuel up fine??

Just seems that when connected to this outboard that the primer doesn't appear to be priming perhaps as well as it should?

[big moose]

Baithrower, probably an air leak in the fuel line between the engine fitting and the fuel pump on the motor

regds

[rhycebullimore]

souds like an air leak that could possibly be after the fuel filter as you said you can see the fuel making it to the fuel filter.

[CreelReaper]

For mine it will be the rubber diaphragm in the fuel pump. It is probably old and deteriorated. Hence why gravity fed fuel works ok. Either strip it down or get another pump mate.

Shane

[BaitThrower]

Funnily enough she started first pull today on the second gas tank, no choke needed either and didn't seem starved for fuel... I'm thinking now the original gas in the original tank it came with may have been way old and lost pretty much all its octane and causing hard to start problem.

Kicked over first pull on newer gas.... Hmm

[stevej]

old fuel wont cause a bulb not to go hard

[rhycebullimore]

definitly not, perhaps some gunk in the old fule blocked ya leak for you...lol, still think there is a bigger porblem