Recently bought a 2002 vyper with twin 496 mag ho's. Having a problem with coolant temperature gaffrig gauges. At night when you turn on the dash lights the temperature gauges for the engines go up 20 degrees and it goes over 180 degrees which causes the overheat light in the middle of the gauge to come one. When you turn the lights off the temperature drops back down to a normal reading. Anyone run into this? Any help or advice on how to fix would be great.

Thanks

Yep,been there done that!
You need to run a thicker ground wire to the dash.

Where did you run the ground from and where did you connect to at the dash?

I did not run the ground or install the gauges ,we just bought the boat few weeks ago.Had the boat down at loto when we noticed the gauge problem.

My 290 always did that. Fiqured it was normal and never worried about it. Did not do much night boating though.

My boat with nav. lights on bumps up the temp on the engines about 10-15 degrees warmer on the gauges, and when I run the blower motor my gas gauge drops about an 1/8 of a tank.

Clean all the gauge connections and grounds, should fix it.

Ran a new ground wire ,fixed the problem, Thanks