What is does this ring do?

[marcusknight]

What is does this ring do? What is it called? Diffuser Ring? Do they come on and off? What do they do?

 

[jimmbo]

That's an older style OMC prop. That ring was called a convergence ring by OMC. It diverted a small amount of water inward to contain the engine exhaust and prevent it from getting to the propeller blades. On some later props the ring was reversed and acted as a flare. The are held by tabs in a groove and they can be removed. My dad's 1980 35hp prop lost the ring, it didn't affect performance in any way. Mercury Props and most 3rd party props have a flare in that spot. Some props, like RAKER have no flare or converging ring.

 

[Texasmark]

When OMC came out with the SST (Stainless Steel Teflon) prop.....1973 to my recollection, at least that's when I became aware of it and bought one, Mercury already had the flared tip to accomplish what jimmbo said. One would initially think that OMC had to be different for competitive reasons, or possibly Merc. had a patent still in force for it. Later on most of the OEM alum. lineup had the divergence ring too.

Around here, on bass boats especially, on the SST, lots ran without it when they would get knocked off from logs while fishing the rough and apparently nobody cared enough to replace them, so they must have been overkill or were provided for some extreme circumstance, ventilation problems for some applications?????

 

[jimmbo]

From a 1968 brochure.

 

[Texasmark]

Now that you mention it, it does jog my memory. Must have had one on my white alum too, before I bought the SST. From the ad it sounds like OMC was interested in filling the void to prevent drag. If that was the problem, why did Merc flare theirs and they were there first and haven't changed since? I don't know.

 

[marcusknight]

I can buy the ring, either Lexan or Aluminum. Not sure which to get. Any thoughts?

 

[jimmbo]

1968 till about 1978 the rings were aluminum or bronze, afterwards they started using the Lexan. Myself, I would choose Lexan, or leave it off

 

[Texasmark]

I'd leave it off too since it has been proven on who knows how many bass boats running 50 through 135 hp of which I am aware, can run without it without problems.