typicaly if a pump is bad it does not pump.

restriction on suction side would probably burn the impellar and cause hot or overheat condition.

water inlet hose crusting is known as BRAVO FEVER.
that may be cause, but back flushing will remove blockage but will not diagose a colapseing problem due to the fact of the pump applying vacume thru that hose when engine is running and back flushing is pressureized which will blow the hose up not colapse it.
flucuation sounds like starvation. possibly cracked pumphousing or loose sea strainer lid. maybe slit/ cracked hose.
run engine on hose using a bushing of sorts to rduce the diameter of inlet hose to pump. this way your omiting the transom assembly and drive. this will tell you wher to look for the trouble. then start closely inspecting.

good luck,

Okay i pulled the goose neck off the gimbal housing but did not find any salt or corrosion that would cause a resistance. I put everything back together and double clamped the raw water pump hose to the goose neck. Then I submerged the drive in a large tub if water and started the motor. At first I thought the problem was gone and thought the double clamp did the job but after the motor warmed up, the water pressure gauge started to drop again and the risor got hot.

Monstaaa, I am going to try your suggestion tomorrow by eliminating the transom and connecting the raw water pump hose to my water tub and see if the problem goes away.
Thanks for the advice and I'll post results.
Gary

I eliminated the transom and connected the raw water pump hose to my water tub. After the motor warmed up, the problem still showed itself. I took the pump off and opened it up. I found 1 impeller vane broken off and the piece floating around inside the pump housing. At that point I thought I solved the problem. Installed new impeller and started it up. After warmup, the problem is still there. URRUGH!
I am stumped............