Steve, you made me chuckle on that last comment of yours.
I made a brulap bag cover for my Grumman 15' from bags I purchased at the local feed mill in Mason County in the '80s. Over half my rig of decoys consisted of bleach bottles painted as "black and whites", strung on longlines with a couple dozen Carry Lite mallards. I shot a number of birds on the local lakes and Pere Marquette marsh in the Ludington area over that setup wearing my J.C. Higgins canvas waterfowling parka! I also remember how heavy that cover was when it soaked-up water.
Bill, a good commercial seamstress can sew 1000 denier Cordura together to make a very functional cover out of a couple of yards of material, once you arrive at a price and supply the motor dimensions and materials. My wife made several decoy ponchos (5)for us from 900 Cordura on her machine. One even played a key role in saving my life on a solo hunt in NoDak a couple of years ago-still has that mudhole's contents imbedded in the fabric.
Short of losing it over the side of the boat, a Cordura engine cover should last the remainder of your time waterfowling. The one on my TDB was new in 1994-still is going strong.