Voltage gauge drops and temp guage rises intermittently

[kdrake]

My 22i 2004 boat has an ongoing problem with a sudden voltage drop showing on the dash boat gauge and a 25 degree rise in the temp gauge. It happens after running the boat a while and will sometimes return to normal after the engine is turned off and restarted. Voltage at the alternator reads 14.5v, but on the back of the instrument gauge it reads low (11v or less). Currently can not tell if temperature is in fact rising or not.
I like to fix my own engine issues, but this one is baffling me. Has anyone seen this problem before.

[ajholt7]

If the temp is rising and the voltage is dropping, are you sure your belt is not slipping?

[kdrake]

Yes, absolutely sure the belts are not slipping. That of course was my first inclination. While voltage gauge was low, I checked the output of alternator and it was holding constant at 14.5v before and after voltage drop was indicated on gauge. I have measured 14.5v at the accessory panel. I would like to check if the temperature is in fact rising, but have to figure out a way to measure it seperate from the instrument panel. Maybe something is up with the Engine Control module?

[andrzej77ff]

I am having a similar voltage problem myself. Voltmeter shows about 11 volts but Alternater is putting out 14.6v along with the rest of the system.

[IDBoating]

Get a second voltmeter and monitor both of the voltages simultaneously.

If you confirm that the alternator remains constant, then it sounds like you have a bad ground or a corroded positive connection somewhere. There must be an additional resistance somewhere across which the voltage is being dropped. Standard Ohm's Law stuff.

Report back on the dual voltmeter test. Cheap DMM's are available at Harbor Freight - less than $5 each and good enough for this test.