Which thermostat

I just purchased an 89 Regal A

I just purchased an 89 Regal Ambassador. It has a 5.7L Mercruiser Alpha with Thunderbolt ignition.
I know that these engines are based on 5.7L Chevy engines and therein lies my problem.
I was going to do some maintenance on this engine and It looks like a 140 and 160 degree thermostat is available. How do I know which to get?
The serial is OC714116.
This site shows a 5.7 GM and a 5.7 MIE.
I assume I need the MIE but any help or suggestions would be appreciated.

"Remove the thermostat and rea

"Remove the thermostat and read the number on the bottom; replace w/the same one. There are 3 designs for your engine.

Or, search at the site below.

http://www.mercruiserparts.com/SelectModelType3.asp?class_id=1"

"I am looking at changing out

"I am looking at changing out the impeller and anything else that looks worn in the outdrive water pump in my 5.0L Mercruiser this off-season. It overheats at 3000+, and the impeller's never been changed since 2000 (!). I am also going to pull the elbows and inspect/replace, since rust is showing at the spot where the starboard elbow meets the manifold. SHould I keep going and pull the manifolds, or will I be able to see pretty much if they're blocked up without pulling them?
Any tips/tricks/ things to watch out for on the impeller job? I'm a fairly accomplished shade tree mechanic, and I have a good set of tools, but I'm new to boats."

Vinny:

It's customary t

Vinny:

It's customary to start your own thread to get the most responses. I hope that by waiting to change the impeller after the engine is running hot that no damage has been done to the rest of the engine. Put in a complete impeller kit that has the top and the bottom. Follow the manual instructions. Pull the manifolds while there and send all pieces ou to a radiator shop for cleaning and pressure testing.