Tim, I have an M17 (Hull 626, 2004), but I imagine the opening for a porta potti is the same on both our models. My Thetford Model TC 26104 Porta Pot just fits, although I don't know if it is still made. It is 15" front to back, 12.5" wide, and 12" high (must be 2.5 gallons). Thetford and SeaLand both make units of about that size, so I think you should measure your spot just to make sure 1/2" or so difference is not that critical. You might also look into the waste absorbent packs that were in vogue awhile back, if they are still available. We can also hope Dave Scobie is not on a cruise, 'cause he knows about all this stuff. Tom Jenkins June Lake, CA On Jun 16, 2013, at 3:24 PM, Tim Erwin wrote:

Hello from the Texas Redneck Riviera The year model of my boat is a 2007. There is a recess where the porta potti should fit, I assume. I would appreciate it if someone could save me some time and just tell me make and model that fits. Thanks Tim Erwin. 2007 m15. ( Dark Star ) # 641 Rockport, Texas