Yes your model pumps when it needs, NOT a constant flow. It'll start to pump very hot, then stop as it cools.
To check the impeller is working, remove the stat (2 x 10mm bolts, however leave the rubber seal in place, or it will leak) and run it in a test tank. You'll get a strong, constant flow. Then test the stat, re-fit and run engine.
Some prefer a constant flow, so they remove the stat. You'll run into problems long term if you do this as its designed to run at the right temp, which gives best fuel, performance etc. Some refit a restrictor to slow the glow, giving a constant flow at the right temp.
This model never blocks on the tell-tale, as the outlet is huge!
Peter @ Boatsandoutboards4sale