Worn fuel tank fitting ID'd, + tank choice

[Alan]

Hello to all;
I’ve finally diagnosed my fuel tank fittings as worn, causing fuel to leak out when hooked up to the fuel line, and (I’m now pretty sure) air to leak in while the fuel pump is pulling,. Motor has not wanted to get up to full power. This has not been helping me complete what has been a challenging project. Good thing I’m hard – headed. I measured mine at the fuel inlet with calipers and compared them with new ones. Mine are smaller by several thousandths I won’t cry about all the time and money I put into cleaning and restoring these old metal tanks, inside and out. New seals and o-rings, too. I hope someone can profit from this info.
I’m thinking about one large plastic tank, which would fit under the back bench seat. Anyone know of reasons why this would be a bad way to go?
Many thanks!
Happy motoring;
Alan

[frankr]

I’ve never seen one worn to the point of leaking. But I’ve sure seen a lot of them leaking around the pin that gets pushed in when you attach the hose. Look at the pins. One has a small brass washer around it. There is a tiny o-ring behind that washer. It is accessed by removing the core plug at the opposite end of the pin, then remove the pin and then pry the brass washer out. There is also another o-ring in there, replace both while you are at it.

[outboardnut]

https://aomci.org/forums/topic/has-any-one-tried-this-repair-on-a-metal-omc-fuel-tank-not-a-pressure-one/

[outboardnut]

https://www.youtube.com/watch?v=5gprqgjqmHc

[Alan]

Info appreciated.
I learned about the o-rings when I left the tanks in the boat for a couple of days, and one leaked about 3 gallons all over the new carpet and floor I laid. It was not much fun to mop and drain that all out carefully. So, all new o-rings.all round. It gets hot where I live, and now they don’t leak at all. Even when it’s been hot in the garage, I don’t smell fuel or get any seepage..
So, they don’t leak til I hook em up. Even when I release pressure first by loosening the cap prior to hookup. I’ve replaced the line fitting twice.
Anything else I can try before replacing the tanks?
Am I wrong in assume that it leaks air in when the fuel pump is pulling? I’ve noticed times when it seems to be starving, and “squeezing the pickle” helps. And, like it needed squeezing.
I figure I need three tanks. I can get 3 new fuel tank pickups, (for like $99 each). Or 3 new plastic tanks for $50 each, or one big tank for $200.
I’d love to use the 3 tanks I’ve worked on, but am fed up with fuel fumes and leakage, and don’t know what else to do.
It’s been a while, but I’m getting there. My son and I got it up to 23 MPH last time out. I’m not small, and he’s 6’8″. Til the prop let go and we limped back on the trusty ’79 15 hp.
Any suggestions welcome.
Many thanks to all.
Edit; great video! I now see that I replaced the o-ring from the back, but NOT the one at the front of the fitting. I’ll try again on those. Thanks!

• This reply was modified 5 years, 9 months ago by Alan.
• This reply was modified 5 years, 9 months ago by Alan.

[frankr]

Yep the one behind the brass washer is the culprit.

[Alan]

Agreed. “Quad ring”. That’s gotta be the issue. What a relief.
I have parts, (o-ring, quad ring, and cap) for all three tanks on the way. I find lots of parts and info online, and I was very impressed with Crowley Marine. Great webite; efficient and intuitive.
Very much appreciated.
Alan

[RICHARD A. WHITE]

That tank should not build pressure at all…should it?

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[dave-bernard]

It does in the SUN.

[amuller]

As I understand it, one of the pins vents the tank when pushed in, and the other opens the fuel pickup passage. So if the tank is sitting in the sun with no hose connected, pressure can build. If the vent valve is tight and the fuel valve leaks, fuel will be forced out–potentially quite a bit. Leaving the cap loose should prevent spillage, or you can use a cap with a vent screw from the small tank sold with the smaller motors.

This is why most tanks, other than these OMC designs, have a vent screw in the cap. the OMC tank design is clever, and convenient when everything is right, but there are a lot of bits to be right.

[Author]

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