My thermostat was stuck open the last time I had the boat out, so I pulled it off today and freed it up. (Odd that it was stuck open as it was new) Got it freed up and re installed. Ran it on the hose to make sure all was well and noticed the starboard manifold was hot...too hot to touch for more than 2 or 3 seconds. Port side was cool. Got out of the boat to check flow and clearly the hot side was lower on flow. This is a stock 454 mag with Keith Eickert aluminum manifolds. My question is, what keeps the flow balanced side, especially at idle speeds. I was thinking about adding some restriction to both hoses to help keep things balanced, but am concerned what effect it will have at wot. Any thoughts?

possibly either sand or scale restricts flow of water, notice it on alot of older engines. was discussion couple weeks ago on same thing. better to find restriction than put more into system.