Re: impeller test with prop off,,,,,, '58 johnson 7.5hp AD-12
HI MadTom. Welcome to iboats. Your impeller should be fine. When the motor has the prop on the prop can/does force water into the uptake, particularly when it's in FWD. However, it should still pump water when in neutral. Running the motor without a prop is essentially the same as running it in neutral (i.e. no spinning prop to influence water uptake) so it should still pump water. The impeller runs due to the rotation of the driveshaft. As long as the driveshaft spins, so should the impeller, regardless of whether or not you have a prop. If there is no water coming out it's because there is something wrong in the cooling system. A lot of times the copper water uptake tube may not be properly seated in the top of the water pump housing after servicing the lower unit. The fins of the impeller can sometimes bend backwards and/or breakdown and clog up the water passages. You may want to drop the LU and make sure you get good water flow by hooking up a garden hose to the copper tube. you should get water coming out of the exhaust. If you do not, you have a blockage somewhere. The impeller may also be improperly seated on the impeller key. I would drop the LU and take a look at the waterpump and housing. you may as well replace the impeller while you're at it. They're only $15 or so and only takes about 20 min to install. you can get one right here at iboats. Check it out and let us know what you find.
