Topic: OMC Pressure Tanks – Antique Outboard Motor Club,Inc

This topic has 19 replies, 5 voices, and was last updated 2 months ago by Buccaneer.

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February 22, 2026 at 5:43 pm #304949
Buccaneer
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US Member
Just went through a Evinrude “Junior” tank and noticed a couple of
things that made me go hmmmmm?

This original diaphragm (or at least the one that was in the tank)
- has an extra hole in it, that lines up with a dome with a hole.
  The new diaphragm I have does not have this hole.
  Just curious as to what’s the deal with that?
  Regardless, the primer works great with the old diaphragm.
- This cap had no chain nor slot in the washer to attach one.
  Were the Junior tanks like that, or someone switched out
  the washer and eliminated the chain?
  
  VIDEO of Primer Test
- https://youtu.be/lZWowGmplXg
- P.S.- No idea on “how” I got the “bullets”, nor any idea on
  how to get rid of them.
Prepare to be boarded!
February 23, 2026 at 7:05 am #304959
Steve D
Participant
Hey Buc, I’ve never seen an extra hole that you’re referring to in the diaphragms. The only extra hole is in the earlier diaphragms for tanks that had the aluminum push rod like that tank, and not the black plastic button. And the Junior tanks did originally have slots and chains just like the 6 gal.
February 23, 2026 at 8:41 am #304962
Steve D
Participant
The slot’s not shown in the parts diagram but they were there…
February 23, 2026 at 10:14 am #304966
Buccaneer
Participant
US Member
Thanks Steve,
That diaphragm with the extra hole must have had
a use in some application at one time, as it’s directly in line
with a dome in the casting.
Not worried about it, as it works as is, but was curious.
I guess I can make a slot in my washer for a chain.
Just have to find a chain now!

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February 23, 2026 at 10:21 am #304967
Steve D
Participant
I’m sure I must have one in my extra tank parts I can send you in a stamped envelope.
February 23, 2026 at 10:26 am #304968
labrador-guy
Participant
US MEMBER PAY BY CHECK
Well Buc I spent the cold aspect morning looking at my old pressure tanks. I have three four gallon tanks. I think that is what you are referring to as junior tanks. I have two with plastic buttons and one with an aluminum button, all have the chain attached to them. My old memory banks told me somewhere amongst these tanks there are some without the chain. I found them, they were from the early 50’s. One came with my 14hp rude. The other came with my 51 25hp rude. The boys will correct me if I am wrong but the tank we now call the tall boy was first, probably around 49 or 50. Then they made a red six gallon shorter with a small decal on it. Does you tank have a place for the cotter pin to hold the chain for the cap? Those chains are kind of a pain if you are pouring gas out at the end of the season. It may have been swapped some time in the past.

No idea what is going on with the diaphragm.

dale
February 23, 2026 at 11:27 am #304976
Steve D
Participant
If you want it email me your address at sdpiazza (at) aol dot com
February 23, 2026 at 12:25 pm #304982
Buccaneer
Participant
US Member
Steve D wrote:

I’m sure I must have one in my extra tank parts I can send you in a stamped envelope.

Steve, Thanks, but I have one new diaphragm left, but am saving it for the next tank
I’m working on, just in case I need it.

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February 23, 2026 at 12:28 pm #304983
Buccaneer
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US Member
labrador-guy wrote:

Well Buc I spent the cold aspect morning looking at my old pressure tanks. I have three four gallon tanks. I think that is what you are referring to as junior tanks. I have two with plastic buttons and one with an aluminum button, all have the chain attached to them. My old memory banks told me somewhere amongst these tanks there are some without the chain. I found them, they were from the early 50’s. One came with my 14hp rude. The other came with my 51 25hp rude. The boys will correct me if I am wrong but the tank we now call the tall boy was first, probably around 49 or 50. Then they made a red six gallon shorter with a small decal on it. Does you tank have a place for the cotter pin to hold the chain for the cap? Those chains are kind of a pain if you are pouring gas out at the end of the season. It may have been swapped some time in the past.

No idea what is going on with the diaphragm.

dale

Dale, I’ll have to check regarding the “hole” in the tank for the cap
safety chain.
My junior tank said “3 point something” gallons on it.

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February 23, 2026 at 12:29 pm #304984
Buccaneer
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US Member
Steve, I have some other “non pressure” tanks in a pile. I’ll check
to see if any of them have chains. Thanks for the offer.

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