Making a test plate for a Johnson RD-24 and others

[todd281]

I have several older outboards here [33 and 40 hp] Johnson and Evinrudes. I find that getting them in and out of the test tank can be a problem . Often I get them in the tank and then spend a few days fussing with magneto or carburetor parts, dropping small stuff in the tank,fishing it back out with a magnet when possible. I have made a plate to attach to the side of the gear-case.A hose attaches to it and a filler goes behind it to prevent the water for exiting through the prop inlet in the exhaust.
I bolted this to the outboard, removed the thermostat , plastic thermostat housing, and the button under it. turned on the hose ,expecting water to exit from the thermostat housing.. nothing. I tried turning the motor by hand with the hose still charged.. still nothing.I then removed the hose and fed the water through the thermostat housing and it ran freely to the attached plate. I am thinking perhaps the water will not pass the impeller. However the question is should it be OK to test run the motor using this plate? I know I can not tune it.and don”t want to run it for any extended periods, I just want to test it to make sure its ready for the test tank

[amuller]

I suppose you are right that water doesn’t want to pass the stationary pump. These pumps are positive displacement devices when stopped or at low speeds. I think it should pump OK when idling as long as you can supply water, generously, to the suction side of the pump.

[frankr]

Yes, a non-rotating impeller will block the flow. As for the other tests you have invented, I’d have to ponder on those a bit. Are you aware that that is a re-circulating system? Water returns to the pump INLET side, through the second water tube when the thermostat is closed. I guess that is what is happening when you are dumping water into the head. BTW, that plastic thermostat housing and check valve must be in place for the system to operate properly. Without those parts, exhaust can travel down through the second water tube and enter the pump.

[frankr]

A water pump does not “pump” when connected to a garden hose. It only allows hose water to pass through.

[todd281]

thanks for the replies , I will only be using this to make sure the motor fires and “runs” , then it will go into the test tank for to make sure the pump is working properly and observation before mounting and running in the lake.thus saving me from having to lift and dunk these in the test tank just to find that they need more tinkering before the will operate .

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