Will do!

I only got to run WOT once this year before I noticed the fuel press issue. I have to get it done, but then agian, maybe not having tje fuel systemset up for WOT is a good thing....

Diffuser rings were designed to dissipate exhaust gasses away from the high pressure side of the blades. I doubt your running the exhaust through the out drive.

Diffuser rings help getting on plane whether you have through hub exhaust or not. I have tested many a boat with and without the diffuser ring and those that have a difficult time getting on plane with the ring have an even harder time without the ring.

The diffuser ring is not just keeping exhaust gasses from getting into the blades. If you have through hub exhaust the exhaust port on the drive should allow for air to pass through the drive and exit the drive through the prop. So in this case there is air going through the prop even without through hub exhaust.

If the exhaust port through the drive is closed there is a vacuum and the flare ring helps to prevent the cavitation behind the prop from entering the blades.

If all I had to do was cut the flare ring off to pick up 1-2 mph I could save myself a lot of time working props and just cut flare rings off all day. Expect a negligible increase in speed by cutting off the flare ring, less than 1mph. You may also lose some cruise speed if the flare ring is cut off.

Matt

I expected a response from you Matt.

First, I agree that boats having a hard time getting on plane due to prop ventilation while buried, not from surface air, do benefit from retaining the diffuser flair.

Yes some residual air can pass through the hub and ventilate the blades. Thats why I asked when the ventilation was occurring and suggested if it is bad we should look to other options. In this case the blow out never happens throughout. This application does experience venting from 2200 to 3000, then hooks up. This sounds more like a normal hydrodynamic issue with the hull design aerating the the high pressure side of the blades for a short time as the attitude of the boat changes. Many performance boats experience this as the boat breaks over. Therefore, removing the diffuser may or may not effect holeshot.

Agreed, if all you had to we had to do was cut the ring to increase speed, we'd all be doing it all the time. I know from years of testing also, we have seen MORE than your stated "less than 1 mph increase". We have cut the diffuser rings off every B1 prop we sell to Spectre for years. Both at Mercury Racing and at BBLADES. We tested it over and over. I'm not sure where you get the notion it depletes cruise speed either.

Now, all that being said, it doesn't work on every boat. That has to be clear. But, if your boat gets on plane easily, why add additional drag by changing the water flow? Especially if your surfacing the propeller, you are creating a down ramp effect across the bottom of the propeller that lifts the stern and drops the bow. hmmmm.

Its interesting the Hydromotive engineers have elected to omit diffuser rings on Intimidator Q4's with a blade geometry that extends well beyond the hub length. What about the rest of the lines they offer.

This response is not intended to make waves, only to suggest removing diffuser rings does have a place in fine tuning propellers. When and where is the big question. The flare is there for a reason. But look across the propeller options you have, they certainly don't all have flares.