I posted a while ago but did a bit more research and field testing today....and came up with a bunch of questions. (I really hate knowing a bunch of stuff and nothing about boats, or at least my boat.
I have a video of the temp gauge activity but don't thing it will help, link available to anyone that wants to watch.
Engine starts fine, temp gauge acts normal. (warms to bottom third of gauge)
shortly thereafter gauge will warm to top third, then into the red, then rapidly back towards the bottom third. from here on out once engine is warm it will do this at any RPM, load, speed, turn etc. idle to WOT. in the course of 2 minutes cycle from cool (bottom third) to hot (top of red)
Although I didn't check at high full speed, at moderate speed (20 mph...3000 or so RPM) risers are hot to the touch with gauge showing hot, then get cold when gauge comes back down. Again this happens at all or any RPM/load though maybe cycles faster at higher RPM.
Engine never acts 'hot' that I can tell when gauge is showing hot (pinging, loss of power, blowing off hoses etc etc) temp light (idiot light) follows the gauge (when gauge hot light is on)
Its my first full season with the boat, so I don't know the history.... it has the suspect VDO gauge pack that seems wonky at best, it did this last year but didn't seem so obvious but I may not have paid so much attention to it. It has a new thermostat in it this spring.
Questions, are there two senders (one for gauge one for idiot light)
could this be 'normal' and just the gauge reading incorrectly
Friend suggested it might be a partial blockage by the water pump....impeller seems obvious as well but it 'felt' real good while replacing belts in the fall, (very snug, hard to turn by hand) thinking of pulling the thermostat next time out, or putting a simple auto style gauge straight on the sender. Read the other thread about checking ohms readings and that sounds like a valid test as well.
mostly checking if there are any folks with similar problems that can point me in the right direction.
**EDIT** added video link....think it does help describe if you have 1.5 minutes
http://youtu.be/OAWY1RG7Mw01998 Four Winns Horizon 200
500+ hours
4.3GL
_________________
Jon Miller
1998 four Winns Horizon H200
Volvo Penta 4.3 GL
Newtown, CT
untitled-545 by
millerjont, on Flickr