Re: Deck fill cap interchangeability
Perko will fit 99% of deck fills on boats made in the US since 1983. The key elements are ID (inside diameter) and TPI (threads per inch).
Although US standards call for 1.5", that only applies to the hose barb..the threaded part is 1.25" EXCEPT on some older boats and many European boats that have wide side decks...they may have 1.5" theaded fill too. Pre-1980 deckfills all had 16 TPI...and I know from experience that NOBODY still makes a cap to fit. You lose a cap for that one and the only answer is a new deck fill. All today's deck fills are 11 TPI.
It's fairly easy to find out what you have: get out a ruler...measure the diameter of the threaded hole on deck and count the number of threads per inch in it. There's enough difference between 11 and 16 make it pretty obvious which you have.
And btw...this information can also come in handy if/when you need a pumpout connector.
© 2016 Peggie Hall
Specializing in marine sanitation since 1987
Author "The NEW Get Rid of Boat Odors"