Pressure rating for OMC 1950’s tanks

[crosbyman]

George… the concern and topic is interesting but what will you do with the info ??  if let’s say  the   answer is 20-30-50 psi ??   Maye some older fellow at the DOT knows the answer  🙂

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[The Boat House]

I believe the gasket would blow out long before
pressure inside a tank reached the point that a tank
could explode.
Tubs.

[george-emmanuel]

Crosbyman,

As stated at the beginning, my goal is to put to rest rumors that pressure tanks can explode in an article I’m writing. The OMC tanks all  have a built in pressure relief valve that vents at 7-9 psi per conversation with 2 retired OMC techs. But to more fully explain the safeness, I need to determine the maximum rated pressure for the tank, so I can show the margin of safety. So, for example, if the tank were rated at 36psi, there would be a 4 to 1 margin. I’m confident there is a rated pressure, but I’ve got to find the person who knows, and now that OMC has been long gone, I may not.

I’ve been trying to track down a friend of mine who was V. P. of OMC’s Performance Group which manufactured the racing engines and were doing the testing of the prototype V-8’s in hopes he might know. I’ll keep my fingers crossed!

George

 

[reivertom]

These tanks are one of those things that people have worried way too much about for many decades, sort of like getting stuck in quicksand, drinking from garden hoses, getting VD from toilets seats. You get the picture.

[fleetwin]

The Boat House wrote:

I believe the gasket would blow out long before
pressure inside a tank reached the point that a tank
could explode.
Tubs.

Tubs makes a good point indeed, seems like the gasket would blow out first before the tank could ever rupture.  Like others have pointed out, outboards are only capable of making a certain amount of crankcase pressure, which is relatively low.  Today’s volatile fuels combined with hot weather are probably more of a danger than excess crankcase pressure.  Like others have also pointed out, look at any of today’s plastic tanks that get bloated on a hot day, seems like the plastic would give way long before the sturdy two line pressure tanks of the 50s.

All fuel systems have to be properly maintained, and vented properly to avoid fires/explosions.  My guess is that many fires/explosions were blamed on the pressure tanks, when maintenance, venting, and improper fueling were actually to blame.

George:  I hope you get the information/specs you need to dispute this long standing myth about pressure tanks “exploding”, wish I could help.

[frankr]

fleetwin wrote:

The Boat House wrote:

I believe the gasket would blow out long before
pressure inside a tank reached the point that a tank
could explode.
Tubs.

Tubs makes a good point indeed, seems like the gasket would blow out first before the tank could ever rupture.  Like others have pointed out, outboards are only capable of making a certain amount of crankcase pressure, which is relatively low.  Today’s volatile fuels combined with hot weather are probably more of a danger than excess crankcase pressure.  Like others have also pointed out, look at any of today’s plastic tanks that get bloated on a hot day, seems like the plastic would give way long before the sturdy two line pressure tanks of the 50s.

All fuel systems have to be properly maintained, and vented properly to avoid fires/explosions.  My guess is that many fires/explosions were blamed on the pressure tanks, when maintenance, venting, and improper fueling were actually to blame.

George:  I hope you get the information/specs you need to dispute this long standing myth about pressure tanks “exploding”, wish I could help.

Amen.  My, how many tanks have I seen that have the bottom rim rusted away from sitting in the mud, blood, salt water and beer in the bilge.  It’s easy to imagine how the bottom could blow off.  In reality though, it probably starts leaking in the most rusted spot before it blows up.  You still get a boat full of gas though.

[billy-j]

What’s the difference between a 2 line pressure tank with the cap screwed on tight and a 6 gallon single line steel OMC tank sitting in the sun with the vent screw tightly closed? I will tell you. The 2 line pressure tank will vent to the atmosphere when the 4 to 6 pound pressure moves the relief check valve off it’s seat.  The single line tank will continue to build pressure beyond that. Looking to see when a tank explodes from pressure is not a realistic concern with a properly functional and maintained tank. Either tank set up if it built to much pressure would just push the carburetor needle seat off it’s seat and gas would leak out of the carburetor vent. It’s funny 2 line pressure tanks were never an issue till the single line tanks came out. The only problem with a 2 line tank is that they are 60 years old now and would be mechanics do not understand how they work and half ass try to fix them and do not know how to test them and get mad at them when it does not work right. To bad nobody wrote to that show Myth Busters and asked the to do a comparison of safety and pressure. Would have been an interesting show.  Regards Bill,

[crosbyman]

personnaly the first time I started with oldies (10hp)  and 2 line tanks  I would park my tilted trailer   to drain rain water  out the boat and one   dayI found that 5 gal of gas  had drained out also.

A small rusty pin hole under  pressure gave way and out came  the fuel during a hot summer day.

Conclusion: 2 line tanks  are fine  just like  one line tanks  but  keep and eye on the bottoms. I was lucky  my drain plug was out and the fuel went into the grass ( no tgood  for worms, grass and water table)   but at least I did not go up in smoke.

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• This reply was modified 2 years ago by crosbyman.

[The Boat House]

No matter what documentation George my be able to provide,
or even any demonstrations he may attempt to alleviate their
concerns, I can tell you from past experiences, he’s not likely
to change many minds. When fear is involved, better to be
safe than sorry, trumps any evidence to the contrary.
Tubs

[ede]

George, I believe you will need the engineering drawing for the tank.  It contains the specifications to include the grade of steel for construction.  I believe it will be a standard grade.

Did OMC  stamp out these tanks or did they buy from a vendor and then finish assembly?

The above thread does have merit for tank safety and as pointed out it is usually a human error.

Ed

[Author]

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