Overheating, water temp sender?

It absolutely reads way hot when the nav lights go on, nearly gave me a heart attack but I'd heard on this forum that happens. Is it the small wire gauges that cause that or do I have an alternator issue? This is something I knew I'd have to dive into

Thanks 8122pbrainard I have noticed the whole time I've owned the boat the voltmeter no the dash reads pretty low.

any advice on replacing the water temp sender. I see its brass and its been there for thirty years. should i use some dope on the threads being dissimilar metals and all. i just have this image of me shearing that brass and having a hole in the top of my motor that id have have a pro fix.

infrared gun says its 108-130 degrees right at the water temp sender. the top of the intake manifold runs from 100-118, the ports at the bottom of the exhaust manifold got up to 348 but mostly stayed down around 200, tops of the exhaust manifold read a real cool 68 degrees. the oil filter read 120 at idle, revved up the oil filter read 158 degrees. hose water was 48 degrees air temp is 70 in the shade. i think a new water temp sender will read more accurate because the gauge was reading 180 the whole time

The larger tranny cooler is not a problem, however the 1" shouldn't have been hard to find... The added fittings and joints are more places to pull air, which would result in a warmer running engine.

Senders are cheap but I would also be doing some verifying of the actual temperature
skidim temp sender

anyone replaced a water temp sender before? i have 1500 hours plus on my 88 ski nautique. I've owned it 5 years and the hour meter hasn't moved. idling in the driveway running 40 degree water from the garden hose for an hour the temp gauge says 180. it did climb to 190 before the thermostat opened for the first time. the impellar and thermostat are new last summer. Im thinking replace the water temp sender and try again. I paid 160$ two years ago for winterization and upon initial startup last summer i saw the dummy forgot about the tranny cooler. It froze and split the solder so it did get warm last summer but i immediately shut it off and let it cool, fixed the tranny cooler and it ran like a top all last year. i kept a close eye on the temp and it did seem like it was consistent reading 180. hoping its just the water temp sender anyone know the specific part number?