You really need to install a water PSI gauge to check things out. Could be
thermostats, passageway restriction, headgasket. Go to www.screamandfly.com
as there are many OB guru's there

"mjb920" wrote in message
oups.com...
I have a '97 Pro-Line with a 150 HP Merc that has recently experienced
overheating problems. It idles at about 150F, and gets up to over 180F
at higher speeds before I idle back down. I am guessing it has both a
water pressure and a water temperature alarm, because sometimes the
alarm goes off right away when the motor is started cold, sometimes not
until the temp gets over 180F.

I replaced the impeller, which made no difference. The pee stream seems
hot and not as strong as usual. Is there anything else I can check?

Thanks,
Jim