I have a 89 Merc black max 200 great shape the only prob is that the starter spins free like 30 times before it will catch and start.

Seems to be getting worse also it seems to be heating up could it be the gauge not reading right or is it getting hot.

Motor was gone through last may had new impeller put in seals and what not I checked the thermastats and the work right they open at the spec temp

With a motor that old I'm not sure what to tell you about the over heating part but here are some answers for you:

#1. The starter: check the starter ring itself, maybe the splines have been broken and you may need a new ring.

#2. The overheating issue: Check your water pump on the motor, your boat may not be circulating water into your motor. water circulating into a motor is like a fan for a motor to cool it down.

8-)

Check also the starter drive gear. It is on the starter shaft with spiral splines that push the drive gear into the ring gear on the flywheel when the starter turns over. It may be sticking on the starter shaft and unable to move into the ring gear. The drive gear should freely move out the starter shaft against the return spring.