OMC 6 gal. tank with Merc 9.9 - problem

[lakelover]

My 9.9 came with a 3.5 gallon gas tank. I wanted a larger tank & had an OMC 6 gallon metal tank with a relatively new hose, so I bought a mercury fitting for the motor end and hooked it up.

I took it for a short run and it seemed to be OK, so I docked it. When I came back later, gas was dripping out of the motor through the carb until I unhooked the gas line. I had been told this setup should work, but it seems there was too much pressure in the tank or something. Switched back to the 3.5 gal. tank and it has been fine since.

Was it because the Merc tank is vented and the OMC is not?

Thanks.

 

[lakelover]

Re: OMC 6 gal. tank with Merc 9.9 - problem

Sorry, I guess I should have put this in the Merc Outboard discussions...

 

[5150abf]

Re: OMC 6 gal. tank with Merc 9.9 - problem

Was the vent open?

There shouldn't be pressure in either tank, check the vent and see if it is plugged or not open but it has to have a vent on it.

The tank you run is irrelevent, I run a 6 gal Yamaha tank on my Evinrude, as you said you just change the hose end.

 

[lakelover]

Re: OMC 6 gal. tank with Merc 9.9 - problem

There is no vent on the OMC tank that I'm aware of. I don't know if they have changed since then, but it was probably made in 1965. Before this, I have always run OMC motors and have never seen a tank with a vent.

 

[CatTwentyTwo]

Re: OMC 6 gal. tank with Merc 9.9 - problem

I have a much newer OMC tank, but my tank is vented when the quick connect fitting is attached to the tank.

 

[David Greer]

Re: OMC 6 gal. tank with Merc 9.9 - problem

on the old OMC tanks you just leave the cap loose.

 

[tashasdaddy]

Re: OMC 6 gal. tank with Merc 9.9 - problem

old omc tanks are vented thru the cap, you cannot see it, but it is there. what it sounds like is your float needle is stuck open, or the left the motor tilted. when the motor is tilted the carbs are not level, and the float needle opens allowing gas to flow.

 

[steelespike]

Re: OMC 6 gal. tank with Merc 9.9 - problem

I would suspect the both tanks had a vent in the cap that can be closed. The small tank was left open the larger one may never have been opened.The float may be suspect and leaks when the sun builds pressure in the tank. I have a Merc 500 with one or more suspect floats.It runs perfectly except if you squeeze the primer bulb too much gas will drip from the carb area.I leave the tank vent cracked slightly or unhook gas line.Boats been in extended storage so I haven't been able to investigate.