I just replaced my water pump on my '97 OHV
Vulcan 3.0 (164k). The original factory pump came out with intact impellers, however each right-angle bend on each impeller had a rusted hairline crack through it - which probably reduced flow somewhat. Hard to believe the water pump pictured is real. Why would ALL the right-angles on ALL the impellers be completely rusted off so perfectly? Very hard for me to believe.
My car has had no-heat (or greatly reduced heat) issues over the last several years for the same reason every time: block heater core. The cooling systems on these cars just continually sludge up. You need to stay on top of it by flushing at least once per year. To blow out the heater core I just pull off the hoses on both sides of the heater core and run the garden hose through it both ways to unblock it. I've even made special remnant hoses to do this quickly. You can disconnect up high near the firewall on the passenger side at the hose clamp and near the T-fitting on the H hose on the driver side (also has a clamp). I replaced both factory clamps with screwed hose clamps for easier removal/reinstall.
Flush your heater core, flush your ENTIRE cooling system (it will forever crud up on you) - try using the factory TSB
stuff ("ph IRON cleaner" 2Qt bottle ~$40), replacing the water pump MAY help (it hasn't been cold enough here to prove it has helped me any), and check to make sure your blend door actuator (~$45 from the dealer) is working properly. The BDA
is a white, milky, cigarette-box sized plastic gear box underneath the dash (at center) with a slim silver slotted "bar" attached to it. If it's broken (with a stripped plastic gear inside) you can temporarily prop the door up (heat position) by jamming a piece of plastic in the sliver bar slotted hole (I cut a piece from a plastic laundry container). I actually did this for a couple of seasons before finally replacing the broken BDA