Does my new prop need to have the reverse slotted cup that my old prop has?

[indyboy]

Hi everybody...I have a 1990 Johnson 9.9 hp 2 stroke that needs a new prop due to damage. This original prop has a reverse exhaust cup with slots on it where the exhaust comes out but from the pictures I have seen online the newer props just flare out at the end instead of cupping back with the slots....Are the newer designs OK? Should I search for an original design? The main aftermarket (affordable) prop seems to be made by Solas. Any thoughts on them? Thanks in advance for any and all help! Happy Boating.:joyous:

 

[steelespike]

The pictures may not be an exact representation they are basically just a likeness.
Unless the ring is mentioned in the description don't sweat it.

 

[indyboy]

Well...according to the now 26 old owners manual I have it mandates the prop have the exhaust ring....just didn't know if the newer designs eliminated that requirement.

 

[jimmbo]

You are referring to what was called the divergance ring. It's purpose was to contain the exhaust gas from slipping around to the low pressure side of the propeller blade. Later OMC props took the same ring, spun it around, so it then acted like a flare similar to what Mercury had in its props, which merc said helped suck out the exhaust. Some props don't even have one. Our 1980 35 hp Evinrude lost its ring. Didn't seem to make any difference

 

[indyboy]

Ok...Thanks Jimmbo. I just don't want to order a new prop and send it back because it causes cavitation issues.

 

[jimmbo]

You mean ventilation, not cavitation. Two different things