Temperature Gauge Fluctuating

[scatgo]

Just put a new carb on the boat and now I noticed the temp gauge will change after it warms up. If I bring the RPMs up to about 2000 the gauge will drop to cold engine reading. Bring it back down to idle and the gauge will slowly of jump right up to normal temp of go slightly into red zone. This is on the garden hose. never had this problem on the muffs. The engine is a rebuild with about 2 seasons on it. Not sure where to start looking with this one.

 

[04fxdwgi25]

Check the wiring to gauge and sender unit. Ensure the sender is grounded.

 

[Scott Danforth]

check the impeller.
check your hose flow. are you using a 3/4" hose on full?

 

[KJM]

Just put a new carb on the boat and now I noticed the temp gauge will change after it warms up. If I bring the RPMs up to about 2000 the gauge will drop to cold engine reading. Bring it back down to idle and the gauge will slowly of jump right up to normal temp of go slightly into red zone. This is on the garden hose. never had this problem on the muffs. The engine is a rebuild with about 2 seasons on it. Not sure where to start looking with this one.

What engine are you talking about?

 

[Lou C]

Sticky thermostat prob has nothing to do with the fact that you changed the carb, unless you may have bumped the wiring for the sending unit in the intake manifold. Sometimes you get a flake of rust or sand that keeps the stat from closing and then the engine runs cold. Sometimes they clear out on their own, sometimes not.