New to me 1988 28' Mariner Voyager. 1 owner boat.

He lost the waste and water caps. The replacements he has are a water one that is too small, and a waste one that is too big.

I've searched this forum as well as around the net, Perko and Attwood sites.

I measured the inside diameter of the deck fittings with a micrometer with the waste coming in at 1.749 - 44.38 mm and the water at 1.769 inches 44.98mm.

I suspect the one that is too big is just the wrong thread size, as there are 1-3/4 inch ones out there (rare but there). It had been cranked partly into place but required large water pump pliers to remove I found mention of Atwood as having an odd thread, but found nothing on their site 1-3/4". On eBay I found a 1-3/4 for a Perko speced as fitting a much larger Carver than mine.

Any thoughts would be appreciated. Thanks.