getting hot at idle...5.7 V8 Mercruiser I/O 1993

Question
We recently purchased a 1993 sea ray, great condition, it was dry stored.  We did a tune up on it, plugs, oil change, belts, etc... and some overall maintenance stuff just to be on the safe side before we went out in it.  Engine sounds and runs awesome when cruising, however at idle our temp starts to get too hot, so I'll have to start moving again to lower the temp then goes back to normal again.  I'm an amateur in boat engines, this issue is not normal in my eyes, but I'm thinking it might be a bad thermostat or waterpump going bad, but really not sure....please help with any tips, all your help is greatly appreciated!  thanks!

Answer
Hi Rick

Thank you for selecting the undersigned to respond to your question.

I'm not a mechanic, but your approach toward troubleshooting sounds good. Did you check the fresh water intake for obstructions? Have you checked the bilge for water build-up due to an engine block crack(s) resulting from freezing, from a loose hose connection, or from a defective/cracked hose? What about an engine flush and pressure test for water journal blockages? The thermostat could be sticking, but if the water pump was malfunctioning, there would likely be symptoms of an unusual noise. Have you double checked the tension on all drive belts for slippage?

Failing any results from the above inspections/tests, I recommend you consult a qualified marine mechanic to undertake the troubleshooting process farther. It just might save you big dollars in the final analysis.

Safe Boating
Ron Blanchet