clear warning code from RPM dial (coolant sensor, see dealer

[slim]

I have a 2005 210 running a ZR6 375 h/p, i did my impellor which now has been replaced, a warning code came up in my RPM gauge stating "Cooling Sensor, See Dealer." I now have a situation where my temperature gauge takes a long time to register any temperature causing causing over-fueling and black smoke. I have replaced the thermostat but this problem still occurs until the boat has been running for about an hour. I'm wondering if the fact that the code hasn't been cleared from the gauge if it's still sending a message from the computer to go into a protection mode because it hasn't registered the problem to be fixed (even though it is). How do i clear the code from the dash without using a laptop?

cheers,

Slim-o