Take city water, then have your dock 20 feet below the street water line level, and I get almost 100 psi at the dock :)

-Greg

Globe Rubber Works Blue Impeller
 

You may want to try a Globe Rubber Works Blue Impeller. They claim 15 minutes run-dry with no damage and they make 'em for just about any pump including all Mercruiser models. You can buy them discounted at BoatFix.com.

Yo, you may want to pull the hoses off and check for blockages form the old burnt up impellars. That could be you problem. I burnt up two impellars after I installed my new motor. The culprit was the lack of water flow AFTER the impellar, before the coolers. Impellar chuks got jammed up and the flow was interrupted, making to vacum effect to suck the water from the out drive....at least that's the way I interpreted it. So.....after frying two impellars, I wised up and pulled the hose off of the TOP of the oil cooler and the exit of the impellar, ran the hose and pumped water backwards to flush out what tuned out to be a truckload of rubber chunks. Then I put the muffs on, and re attached everything but left the inlet to the impellar off. Run the hose, see if you have water, it should be pretty much a free flow. if not, you have a jam "upstream" or, towards the gimbal. if it flows to the impellar, and the impellar is installed correctly and hooked up to pulleys correctly (pretty simple, but make sure you hook up the hoses to the impellar housing correctly, should be printed on the back of the housing -- In and Out), then when you fire the motor it should suck up the water right now. IF not, shut down immediately and look for unattatched hoses, blockages, crimped hoses (even a twisty tie can hinder the water flow) etc. Just my (long) .02. Later!

I have used the "cheaper" muffs for a long time, just don't rev the motor very high for very long!
Also, I replaced the inlet that the hose screws onto with a larger plastic hose end that I bought from the hardware store. The hole was considerably larger than the one that came with the muffs.
You will need to drill out the rubber on the "ear muff" that the fitting goes into and then secure the new fitting with a hose clamp to make sure it holds.
I also have town water with good pressure, so I'm sure that helps!

You may want to check the pump bearings. Doug

Go for the fresh water flush fitting. It is the best thing going.