Thanks for the help, got the vent replaced today, just in time for the next rains. Lots of measuring lead to the right part on the first try, so thought I'd let you all know that Heng's part #58621-C2 worked perfectly for my Dolphin, let it rain.
I've got a 1984/85 Dolphin, and need to replace the forward escape hatch and assembly. I've read on this forum about the Elixer 17x24, but it looking around it seems like the one by Heng's might be a closer match: http://www.ebay.com/itm/roof-vent-ESCAPE-Hatch-white-lid-metal-frame-rv-bus-Hengs-48621-C2-/221258719528 . Any help or experience would be very helpful in deciding which to order. Thanks