My bad, was thinking of the newer 5xx and 4xx series units, the 498 does have a non-optional sounder, but maybe he didn't install it.
It has non-optional sounder support, but, depending on the package you buy, it comes with either a transom-mounted sonar, or, as in my case, you have to buy the transducer separately. I did buy the dual-frequency in-hull transducer, but that comes with quite an involved installation procedure. (Part of which involves going out somewhere on the lake that's at least 30' deep and staying put. I'm a stickler for details on this kind of thing, so I'm going to follow the recommended installation/alignment procedure.) That's why it's not in yet.