Check your power steering cooler inlet screen!!
 

Ok so I fired my boat up for the first time in 7 months a few days ago...I had the "fake a lake" attached and the hose going full blast. After a few minutes I noticed I was BARELY getting any water out of the exhaust, then noticed my manifolds were getting hot to the touch so I shut it down right away. I couldn't imagine what the problem must have been since I JUST changed my raw impeller one year ago. I decided to check the inlet for obstruction on the power steering cooler, and look at what I found!!!

It turns out my one year old impeller literally blew to pieces, and all of them were cought by the screen in the cooler. Not only was most of it lodged in there, but apparently this must have happened in the past and the previous owner never thought to remove them because there were wayyyyy more broken fins/pieces in there. This explains why my motor would start to get slightly hot while idling for extended periods of time. I would have to put it in neutral and raise the rpm's a bit to get it cooled down. So take two minutes, get out there and check for obstructions!!

First pic is what I pulled out, second is a reference pic for anyone unfamiliar a power steering cooler...

Most of these boats dont have power steering (inboards), but good info for those that do own a boat with it.

But they do have a transmission cooler that will do the same exact thing...

Excellent point!

Still enjoying that like new 210? Still think about that boat when I see 1st gen 210s.

yup!!!! our old merc 350 in the old malibu would do that when you shredded an impeller, couple screens in there though thank god.

hahaha I'm an idiot...it's a transmission cooler!! My bad! (used to my old I/O boat!)

I don't trust merc impellers to last longer than a year... other mfrs I have heard of them lasting a long time. 20 bucks is cheap insurance I say change it every year/100 hrs or so..