The Piranha I've brought has a built in bronze/Brass thrust washer at the back with the taper machined into it, although it came with a seperate thrust washer as well. The machining on this seperate washer does not match the back face of the prop in any way however ,and is exactly the same as the old spare thrust washer I have from when I had my old Johnson VRO. It must have just been a spacer for the OMC, and being quite large does obstruct the exhaust ports in the prop.
With the seperate washer, there is not enough thread showing to get the main nut on and a split pin.
Without the seperate washer it all lines up as if it were made for the engine, even the back of the prop sits just inside the gearcase with a couple of mm clearance on diameter, exactly the same as my existing Suzi prop.
I've tightened it up onto the old bottom end for my engine I have in the garage. This unit has a huge lump missing out the side of the exhaust chamber so I can even see the clearance on the bearing housing etc.
Perhaps I should start investigating part numbers.
RIBBED For extra pleasure.
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