digital speedometers on a non Smart Craft motor

[eric80]

Hi, Merc tells me my 2003 115 ELT4TS 4 stroke is a non Smart Craft motor.
so, I can't use Smart Craft gauges.
Does anyone know of a digital speedometer that would work with this motor?

the reason I want digital is I fish tidal rip and the GPS is not giving me water speed.
an analog gauge will be hard to see at 1-4 mph

[boats.net]

Might could use the Yamaha digital gauge on it but probably wouldn't do what you need, it still gets speed signal same as analog gauge which is from the pressure type signal from pitot tube on gearcase. GPS is usually best way to get low speed readings.