Engine test propeller


What differences are there in a engine testing prop used on an outboard engine in a tub of water and a regular usage prop?...........Tom
They should be the same diameter and pitch and blade count. Some shops only use Al for their 'test wheels' as they are much cheaper than the S/S versions.
A regular prop will throw water everywhere if you crank it up in a tank.

A test "wheel", which looks nothing like a regular prop - looks more like a blade from a food processor in "super large" size - will run without making a mess.

Other than that, I can't tell you any other technical differences...
The test wheel is designed to simulate the thrust/drag that the motor and boat get on the lake and allow better water intake than the regular prop does in a tank. Since the regular prop can't get a bite in the tank it tends to over rev the motor. Different motors require different wheels so make sure you get the one for your motor. OMC would use the wheels in their test tanks which are something like 3x3x5 feet or so and hold several hundred gallons of water. Not exactly a large tub or 55 gallon drum. The test wheel can be helpful but you still need to fine tune WOT on the boat in the lake.
Our tank was like 4' deep (3' of water), ~8' wide and ~16' long. We always used the same size (dia & pitch0 as the customer's wheel to ensure the "load" what realistic. Never had a problem with the prop getting a bite or keeping a bite. Yes, even with the lid on, an operating session would get everything wet within a 50 ft half circle of the back end of the tank. Guess times have changed.