Re: Prop Cone Purpose
Do you want the long or short story?
Short story: It makes it look good.
Long story: If you have the one piece lower unit, that is, if your 85 is 1979 or later, it did have a purpose. Those engines (Chrysler 3 and 4 cylinder) had a midleg that was one inch shorter than the earlier models. When first designed, they came with either a prop with an extended hub to match the tailcone or a separate tapered piece to match the tailcone. The purpose was to streamline the gearcase just like an airplane body. But in reality, at the speeds these engines ran through the water, streamlining was superfluous.
Unfortunately, the one inch shorter leg made the props ventilate on a number of hulls so Chrysler engineers designed the "Flare Washer" or "Anticavitation washer." This was a large outwardly tapered black plastic piece that supposedly helped prevent ventilation/cavitation. Depending upon the application, it "sort-of" works. I use it because I like the way it looks and it does not hurt performance.
Later Force engines shortened the propshaft and did away with the tailcone in a money saving move. They also switched to an open hub prop--again, probably cheaper.
Your 85 will have absolutely no difference in performance using the closed hub prop and tailcone, the open hub prop and tailcone or either prop with no tailcone.
So again: Long story---It looks good.
Here are a couple of photos of a Bronze racing prop and a Michigan open hub prop with the flare washer and tailcone that I painted red. The last one shows the original tapered matching spacer on a closed hub Chrysler prop.
The prop tailcone on earlier two piece lower unit engines does retain a drive pin (thrust pin) and the engine can not be run without it unless you use a 5/16 diameter bolt in place of the pin--so it does have a purpose other than looks.
