Prop vents: To plug or not to plug?

[Joe S.]

I have a 16ft deep V runnabout with a 115 Suzuki on the back. I recently purchanced a Michigan Rapture SS (19 pitch) prop thats vented. My problem is that my top end decreased 2mph from my (19 pitch) aluminum prop. Would plugging the vents help performance at all? Anyone had any experience before and after plugging the vents?The SS prop is operating within the specified rpm range at 5100 rpm. Thought SS props were supposed to add performance not decrease it. Thanks!

 

[Joe Reeves]

Re: Prop vents: To plug or not to plug?

Joe S..... If when you speak of prop vents, you're speaking of holes that are drilled in the hub between the blades, they're there to fight cavitation/ventilation. Plug them, try it out. If performance increases, fine. If not, go accordingly.

 

[Dhadley]

Re: Prop vents: To plug or not to plug?

Most likely plugging the holes won't effect top end. They are there for venting on takeoff. The reason SS props increase preformance is that you can run them at a higher X dimension (reduce drag). Try raising the motor (watch your water pressure) and let us know what happens.<br /><br />Good luck!

 

[steve forsythe]

Re: Prop vents: To plug or not to plug?

When you all say they are there for venting on take off, what do mean? What performance benifit is there to have holes in the prop? Would pluging the holes get you up on plane faster or slower?

 

[Franki]

Re: Prop vents: To plug or not to plug?

As I understand it, at low rpm, the prop has less water to push as some goes though the wholes, so the prop can spin up faster resulting in faster holeshot..<br /><br />at high rpms the holes don't make alot of difference as they are spinning to fast for anything much to get through..<br /><br />sort of a cheap mans 2 stage prop.<br /><br />rgds<br /><br />Frank

 

[Dhadley]

Re: Prop vents: To plug or not to plug?

At low speed the exhaust partialy escapes through these holes and vents or airates the blades. This ventalation allows the motor to gain RPM quicker. Once you get past a certian RPM (somewhere around 1200 to 1500) all of the exhaust goes out the prop hub and the holes do nothing. <br /><br />Good luck!

 

[ODDD1]

Re: Prop vents: To plug or not to plug?

Have tried many different vented props on my I/O over the last couple of years...pluggable vented props are kinda neat....with all the plugs in, mash the throttle on take off and you will see maybe a 3000 rpm 'spool up' speed on the tach...the rpm will hang there until the boat gets on top and hooks up......by pulling plugs you can increase that 'spool up' rpm getting the motor farther into the power band and increasing acceleration....and the ability to yank a wide butt on a slalom ski....the down side is the ease at which the prop ventilates when on plane....

 

[jlemke]

Re: Prop vents: To plug or not to plug?

My fishing buddy just tried this, the result, no difference in top end. These props are designed like the others said, for better hole shots.

 

[daschtick]

Re: Prop vents: To plug or not to plug?

I noticed the exact same thing, which leads me to wonder why I bought a Stainless prop in the first place when my Aluminum outperforms it with identical prop size and pitch! I guess it looks cool, and now I have a spare prop, but I almost with I would have just bought a spare Aluminum instead of the high priced Stainless.<br /><br />-Nick

 

[Dhadley]

Re: Prop vents: To plug or not to plug?

Daschtick -- if your aluminum outperforms your stainless something is wrong. Most likely the set up could be improved for the stainless. We hear this same senario many times. It's like a boat that has a good 3 blade ss prop and is set up well. The guy will simply bolt on a good 4 blade and is disappointed. Yet if we spend a little time and dial in the set up, the 4 blade will most likely out perform the 3 blade. You have to maxamize your set up to the style prop you are running.<br /><br />Good luck!