You can get extra keys. I think you can have up to 7. I've seen them online, for about $32 at shopsbt.com (see below). The dealer will probably charge you way too much to program them to your boat, unless you have a good relationship with them. It only takes them a few minutes, but any chance for them to make money…
I've seen a product called the CanDoo Pro (81-200A) from
ShopSBT.com that will let you program and de-program DESS keys. It's $400, but it can do quite a few things for you, like diagnostics, clearing codes, etc. If you planned on doing some work on your boat yourself, it might be a worthwhile investment. Here's some more info on what it can do.
CanDoo Features
Automatically detects the protocol needed without changing flashes
Program Keys / Lanyards
Learning
Rental
Normal
Change Owner Information and Purchase Date
Reset TPS to zero position
Read Fault Codes along with fault data.
Reset Maintance Light
Reset Service Hours
Reset Service Rental Hours
Set Ignition Correction and Curves (2 strokes)
Real Time Engine Monitor
Marry Clusters to ECU's
Last 30 or 60 Sec history
Activate fuel pump, Spark Plugs, Buzzer, etc..
Key Tester
Note:Features are model specific may not apply to all.