You just missed a sale at West Marine for the Lowrance Elite 5, but check out the Lowrance Elite 4.
I have the Elite4 and as long as you waterproof it a bit (mapcard slot), it will serve you very well for GPS and fish finder functions. I get good readings up to about 275' and I'm shooting through the hull with the transducer. With the new transducer mount I bet you'd get much better readings.
How did you waterproof the Elite 4?
Well, actually, I didn't.
I took for granted that the unit is IPX7 rated, so I installed it and went straight into the surf to play. Over the last year it has gotten splashed many times and i've capsized twice. I saw the spare port on the back start to corrode immediately, so I cleaned that and sealed it with a rubber cap. The map-card slot I was not so vigilant about; I thought if it was closed it would be fine... come to find now that its so corroded I couldn't use a navionics chip even if I tried.
Despite that, its a good unit, just do yourself a favor and put a strip of waterproof tape over the mapcard slot and cover the unused port on the back. For the power port, just keep an eye on it. I fish offshore and launch in mild surf, if you paddle/fish in freshwater your experience may vary. The OP sounds like another saltwater user though.