76 Mercury 850 The powerhead will not come loose from the exhaust housing at all. All nuts the hold the parts together are removed. A cherry picker is properly attached. Motor is on the pontoon. Lifting the powerhead raises the entire boat. I've tried heating the powerhead. I used wood to pound the powerhead up from the housing. There are no gaps between the parts at all. What can be done to separate the powerhead from the housing?