Over heating

[wheresmybobber!]

I've got a puzzle on my hands! I've got a 1970 Fiberform with 120 horse chev and merc out drive that has been over heating at an idle. As soon as I throttle up it cools right back down. I thought it may be the thermostat so I replaced it but that didn't help on the last trip. My next thought could be the water pump but that looks like its pretty new. Any ideas would help, maybe theres something I'm over looking.

[riverhawk]

I think you have two water pumps on that unit one on the engine and one in the lower unit

[Boat Doc']

Check the water pump in the drive and also the water supply hose from the drive to the transom. You can see it by turning the wheel all the way to the right. Shouldn't have any kinks or leaks