Plastic Ring on OMC Gearcase/SRX combo - What is it?

[LSaupe]

I recently obtained an OMC V-6 gearcase with a 27" SRX prop. What is odd is that it has a 3/8" thick (or so) plastic ring over the gear case at the intersection where the prop hub enters the gear case (flares-out the aft portion of the gearcase where the prop hube enters). Actually it was installed using an internal extension ring which made the plastic ring set back a bit from the original gear case end point. I had to remove this to install an over-hub prop.

The way it was set up, the ring came right up to the leading edge of the SRX.

I have not seen this used before. Any idea what this was used for and does the SRX really need this to operate effectively?

Larry S.

[Instigator]

blow out ring.

Helps to keep the unit from blowing out at speed.

If you're not running high 80's or better you don't need it and you don't need if to run an SRX.

I think some people confuse "blow out" with "cavitation" which would make sinnce if they were running the SRX.

Being an over hub exhuast prop, it will most likey "cavitate" coming on plane but that has nothing to do with blow out or the ring.

Hope that helps??

Gary


I recently obtained an OMC V-6 gearcase with a 27" SRX prop. What is odd is that it has a 3/8" thick (or so) plastic ring over the gear case at the intersection where the prop hub enters the gear case (flares-out the aft portion of the gearcase where the prop hube enters). Actually it was installed using an internal extension ring which made the plastic ring set back a bit from the original gear case end point. I had to remove this to install an over-hub prop.

The way it was set up, the ring came right up to the leading edge of the SRX.

I have not seen this used before. Any idea what this was used for and does the SRX really need this to operate effectively?

Larry S.

[LSaupe]

Excellent info.

Many thanks for the explanation.

Larry S.

[chynewalkr]

Exhaust Extension Ring - Our gearcase exhaust extension ring effectively lengthens the trailing edge of the standard gearcase housing to reduce the possibility of exhaust gases disturbing the correct flow of water to the blades' leading edge. A deliberate mismatch is also created just ahead of the ring's trailing edge to help collapse any vacuum pockets before they can reach the blades. The correct combination of nose cone kit, transom height, and exhaust extension ring have allowed many boats to exceed 100 mph, using full size gearcases, without blowout! The ring is installed or removed with just a hex key wrench and a few drops of Loc-Tite. This ring fits OMC V6's & V4 "loopers" with V6 gearcase, Merc (except XR-4) and Yamaha V6's.

http://www.land-and-sea.com/marine/vortex/vortex.htm