1990 200HP Yamaha locked up V20

[scubamook]

when I turn the key it just makes a click noise
mechanic says its locked up
he pulled the plugs they were clean
he said it maybe the lower unit that has seized

Is there a way to check the lower unit while the boat is in the water?

I am not sure if it is worth fixing if it is the power-head

It will cost to pull the boat to have the lower unit checked; Is it throwing away money?

Sell or try to fix?

Thanks
Michael