[C320-list] Deck filler O-rings

[islgirl3 at aol.com]

John,Do you happen to have a part # for the Perko green fill cap?
Rich     Barbara Rita897


-----Original Message-----
From: John Morrison <sail-ability at sympatico.ca>
To: C320-List at catalina320.com
Sent: Wed, Sep 2, 2020 7:17 am
Subject: Re: [C320-list] Deck filler O-rings

Another option is to buy the green Perko diesel filler cap. I did that last year as an additional precaution against putting water into the diesel tank. What a lousy design to put those identical caps next to one another, even a different key to get them off would have been better! The Perko comes with it’s own O ring. 
It wouldn’t matter if the O rings on the caps broke, they could still be used for sizing. 
JohnM 
1999#574

Sent from my iPhone

> On Sep 2, 2020, at 5:54 AM, Dennis Cookson <dennis at cooksons.net> wrote:
> 
> Thanks to both Johns for the replies. I think these rings would break if I removed them, they look very old and rather fragile!  But I found this useful list of O-ring standard sizes used in the US, as defined by Aerospace Standard AS568B:
> 
> https://www.sealanddesign.com/page/o-ring-size-as568b <https://www.sealanddesign.com/page/o-ring-size-as568b>
> 
> If we can assume that Perko used a US standard size O-ring on these deck fillers, at the risk of answering my own question the most likely suspect seems to be AS568B -222, which has a nominal ID of 1.5” and cross section of 1/8”.  The actual ID is 1.484” and actual cross section is 3.53mm.  
> 
> The other possibility is AS568B -128, which has the same ID but a nominal cross section of 3/32”, and an actual cross section of 2.62mm. However this appears to be a bit thinner than my existing rings, especially given it would be thinner still when stretched.
> 
> John S - do you think that the 1/8” cross section would be too large for the diesel/water filler caps?
> 
> Dennis Cookson
> #577
> 
> 
> 
>> On 1 Sep 2020, at 12:29, John Stetson <jbstetson721 at gmail.com> wrote:
>> 
>> I just replaced ours.  After a little trial and error, the correct sizes
>> are:
>> 
>>  - Water and Diesel - 1-1/2" by 3/32"
>>  - Waste - 1-3/4" by 1/8"
>> 
>> West Marine did not have the right sizes, but the local hardware store did.
>> 
>> 
>> John Stetson
>> Hull #578
>> 
>> 
>>> On Tue, Sep 1, 2020 at 5:16 AM Dennis Cookson <dennis at cooksons.net> wrote:
>>> 
>>> I need to replace the o-rings in all my deck filler caps, and I can see
>>> that many owners have done this, but I can’t see any info on the size/spec
>>> of the replacement ring.  Does anyone know the exact spec, especially for
>>> the ring fitted to the diesel filler cap on a 1999 vintage 320?  I
>>> measured the outer diameter of the filler cap threads at about 41.3mm
>>> (1.625”) so presumably the o-ring inner diameter needs to be a little
>>> smaller for a snug fit, perhaps 1.6” or even 1.5”?  The cross section
>>> diameter appears to be 1/8”.
>>> 
>>> Are the diesel and water filler caps sizes identical?
>>> 
>>> Dennis Cookson
>>> #577
>