"I have a 888 and like BT said
"I have a 888 and like BT said, you can basicly check everything.
I wanted to find out what was causing the problem so I checked everything one item at a time.
First go-around, nothing major, just everything weak. Old impeller, partially plugged heat exchanger, partially plugged risers, tired thermostat. ( got hot above half throttle)
Second go-around (2 seasons later) tired impeller.
The easiest thing to do is pull the water intake hose and check the volume of water being delivered to the engine from the outdrive. This is usually located just under the heat exchanger. This will give you a good idea on how well the impeller is pumping. If it just dribbles, it is bad or plugged. It should produce a steady stream at an idle and several feet at fast idle. Do this with the oudrive submerged in a plastic garbage can on at the dock.NoT ON A WATER HOSE.
If you ever ran it in the sand, it is a good posibility the heat exchanger is plugged or worse yet if it is a sea water system, the engine block cooling passages are plugged.
Good luck, let us know how you are doing."