Oil pressure and Temp not working

[oceanj]

Twin 350 merc inboards. Doesn't pin just higher than it should be for both.

[Capt. Debbie]

Same thing. Crapped up connections on multiple readings are ground voltage differences,

TEST:
Run a decent gauge wire from engine block to the instrument ground at dash. Essentially your ensuring the block 0vdc is the instrument panel 0vdc. Remember these gauges are reading milli-volts. AKA 1/1000 of a VDC

Originally Posted by oceanj

Twin 350 merc inboards. Doesn't pin just higher than it should be for both.