Re: No water to thermostat
The tips of the impeller look ok. Looks like the impeller hub or whatever it's called is worn not allowing it to spin. Make sure there's a key on the driveshaft.
I see this sort of comment made time and again, and I think it shows a lack of knowledge for how an impeller really works. True, the tips need to be flexible, but that's only one facet of the story...a small facet.
Most, if not all, impellers are offset within the housing. Hard to notice as the offset is very small, but it's there. In the impeller housing on my '91 70hp Mercury, the offset is only like 0.2"...not exactly a lot. A new housing is pictured below:
If you look closely, you can see the offset. So what does that mean to the impeller? See the next pic of a new impeller installed in that new housing with the arms of the impeller "bent" in the direction of travel they'll be in when the driveshaft is turning:
You can see that the impeller itself is offset within the housing, making it vital that the arms of the impeller are flexible, not just the tips. Once the arms take the curved set look like the OP's pic showed, the impeller won't be nearly as effective pumping water, esp. at idle or while on muffs. The impeller will probably still pump water up to the power head once the motor is moving---uses the forward motion of the boat/motor to force water up to the impeller so the impeller doesn't have to work much at all drawing water up to it--but once the boat/motor is not moving (i.e. on muffs, idle, etc.), the impeller is completely responsible for pulling the water up to it through the water inlets on the lower unit. And once the arms of the impeller have taken a curve set, like the OP's did, it no longer seals its tips against the housing wall, making it much less efficient in pulling water up to it.
Then, add in scoring of the walls of the housing from grit, sand, dirt, etc. being trapped between the impeller's tips and the housing during use and the tips don't seal as well, either. So, not surprising the OP's replacement of just the impeller didn't solve his problem completely. The scoring gave an escape avenue for the water to take rather than move up to the power head.
So, tip flexibility is only one very small facet in the overall impeller operation, and probably less important than the overall flexibility of the complete impeller arm.
