'87 Yamaha 150 Running Hot at Idle

[THEFERMANATOR]

My question is always, have you verified that it is actually overheating? Thought those engines were pretty basic with not much of anything to worry about. One thing I would look at is if air is getting in the cooling system. I know failing head gaskets can push air in at slow speeds and cause overheating, but at higher rpm's the water flow is enough to overcome the air getting in.