98 Yamaha 150 Cooling issue

I have a Yamaha 150 w/counter rotating props - 1998. Had good water pressure & no cooling issues after having power head replaced. Within the next 1 year or so, I've had the clutch dog go out. Was repaired at the shop. Pump pressure wasn't as good after that, but was functional w/o overheat buzzer going off. The next 2 uses the pump pressure got worse, had the impeller replaced and carb. reworked. The problem still persists. It doesn't seem as though it is getting proper water to the top of the power head. I'm curious as to whether there are any other locations where water pressure can be lost, other than the impeller. HELP PLEASE - I'm truly frustrated and trying to have my last summer outing with my boys. Thanks for any and all help. I can't help but think it may be something simple that my mechanic is overlooking.

[boats.net]

Once you rebuild water pump the next thing is thermostats and pressure control valve on base of exhaust plate on rear of engine.

[hali285]

have you taken a look at the water tube in the mid housing?? maybe a corrosion hole or bad seal there.................

No spark on my 1998 Yam outboard.

I have no spark at the plugs It was running fine then nothing: