Don't expect an exact plug and play but it can be done without too much hassle if you're able to do some wiring (solder cut and strip the wiring insulators, etc.) I expect. I believe Seadoo's OEM for gauges is Faria, these are somewhat customized to Seadoo specification such as the integrated wiring connector harness and gauge face colors/style, etc., but they're basically a generic marine gauge. So at a minimum, I think you'll be transferring the harness connector from the original gauge over to the replacement gauge.
In the case of the tachometer, there's a switch accessible through a hole in the rear of the standard marine gauge, to configure the number of cylinders or pulses per engine revolution.
The speedometer of Seadoos uses pulses from the speedo sensor, it's not a pressure type pickup. So you need to beware of this and purchase accordingly.
If you look carefully, you'll notice the jet ski gauges are waterproof and boat gauges typically aren't but Seadoo might be using waterproof gauges on all lines, my sportster boat gauges certainly are water proof type.
Seadoo specified an LED element gauge for the oil tank level warning sensor, many other boat manufacturers have implemented other means such as a buzzer or a separate gauge for the engine warning system.
But I thought the Islandia was equipped with a Mercury Sport Jet, thus this system used the Mercury outboard warning/monitor system? I guess if your replacement gauge doesn't have an LED indicator, you could wire the oil tank sensor into the overheat sensor and cause the buzzer ("warning horn" as Mercury calls them) warning in case the oil tank is low.
As long as when your engine overheats and/or oil tank is reaching empty, you receive some notification to take action, you'll be okay. BTW, be sure and test the warning system periodically, nothing's worse than running out of oil or overheating the engine and not having an alarm of some sort to inform the captain!
Lastly, I suggest keeping things simple and replacing only the defective gauge, a full set of replacement gauges can be quite pricey in some cases. Consider each gauge carefully and the specific signals it requires to operate, there are definitely gotcha's that can surface.
