Propeller vents?
 

Can someone give me the low down on what vents do on props? I know the newer ones come with the vent system with a selection of plugs. Do vents only work with thru hub exhaust?

I have thru hull exhaust so would vents benifit me? What I am trying to do is with a 4 people in the boat it takes awhile to get on plane because my motor doesn't start making torque till around 3000 rpm. So I am thinking with the vents in a prop that it will allow the prop to cavaitate and bring my rpms up so my torque is usable to get me on plane faster without having to go WOT and smoke my alpha.. I know our hydromotive came with instructions on how to drill vents in the prop... So i think I can do it to any prop i choose to run..

any opinions?

Thanks

Travis they are mostly for outboards from what I know. They allow the motor to spin up to get more into their power band. Not sure that it will help you.

Jon

sure.. for outboards LOL! damn eggbeaters :p Its exactly what i need to get into the powerband.. or maybe just your 400 lbs girl freind on my bow :p :p

Audio is right in that they allow the prop to spin up, but I think they'll work on any appication that has through prop exhaust.

Sounds like a dead end for that idea.. I guess my boat just became a 2 person boat LOL! me and my little lady for evening adventures :D :D :D :D :D

The vent holes allow the prop to cavitate and spin up to higher rpms faster. I think you can get them on a lot of Merc props. The REV4 I tested last year had them and I have also seen them on newer Mirage Pluses.

The holes allow engine exhaust to ventilate the prop so it can spin up more easily, allowing the boat to plane faster. When the boat attains planing speed the water moving across the prop "seals" the vent holes. Mercury offers different size plugs.

I tried using the vent plugs on my Mercury Offshore prop. The prop ventilated so much I could not get the boat on plane!

P. S. The ventilation system is ineffective on boats running thru-hull exhaust. You need exhaust gas through the outdrive for the vents to work.;)

Traviss,
I had vents on the prop on my last boat. The prop was a Laser II, the boat was a 350 Mag with an alpha. I tried them every different way it found it was best with the vents plugged. I also had thru hull. Boat was still pretty slow out of the hole no matter what plug i put in, just ran a tad better top end with them plugged.

Scott

Traviss,

The newer Mirage Plus props have vent holes in them between each blade. Merc has a part number for plugs with various size holes in them. They do have a significant effect even with through hull exhaust. On the 25 MP if you remove them completely the boat will not even come on plane. I experimented with them some and found that the smaller holes did allow the prop to spin up before really hooking up but decided that I did not really need them.

You could probably drill a non Merc prop to the same size hole and use their plug kit. If you decide to go that route let me know, I can find the P.N. for you.

Tim T.

NOT TRUE !!
 

I have through hull exhaust and tried removing one plug at a time, when I took out the third plug, the boat would not even get on plane.. I now have two of the three plugs removed and it does make a difference, allowing the prop to cavitate ever so slightly to get into the meat of the power band quiker..

Huh??
 

Now I am confused. According to Mercury, the purpose of the vents is to allow exhaust gases to ventilate the prop. If no exhaust gas is present (thru-hull exhaust only), how can the system work:confused:

hmmm this is getting interesting :D :D go on boys :D

Chris,
Do you have dedicated thru-hull exhaust only or some kind of switchable like corsa Q&Q or captains call?

Some switchable systems like the one I have(corsa) will always bleed some exhaust gases through the prop even with the valves open to the thru-hulls.

i know this isnt an answer but... I demoed a rev 4 and the holes were open. Seeing I was using thru hull I thought it wouldnt matter. The boat would barely get on plane and would hardly accellerate at low speed. I duct taped the holes off from the inside of the prop and things were fine after that. Anyone got an answer?????

I had a 27" Mirage Plus with the vent holes on a boat with through transom only. I removed the y pipe and bought the block off plate and installed it. I also removed the exhaust tube bellows because it was no longer needed and the dealer said to remove it. With the plugs out the prop would cavitate badly and could not bring the boat on plane. I think that air from where the exhaust tube (bellows) used to be was being drawn in to the prop. I dont know if the same thing would have happened with an exhaust tube or an exhaust bellows installed.

Ron

I believe rjcardinal hit the nail on the head. I was told that with out the bellows removed it caused a suction creating a great deal of drag. That being the case if the bellows is removed, the air would be sucked into the lower unit and allowing bubbles to vent across the blades. Thence letting the motor to wind up, grab some torque and goooooooo!!!

Travis you can drill any thru hub prop for the same effect. Start with a small hole and make it bigger. If it doesnt work out.. you can use bondo to plug the holes..or use a wire welder with SS wire and plug them with out any problems..

PS. I need to converse about hooking up next week.. I will be headed out on Monday morning and it looks like return on Thursday nite.. sen me a number I can reach at..

Dick

no CC no corsa no bellows no nothing......
 

just straight through transom exhaust...

I removed all three plugs and could NOT get on plane it cavitated so badly... I put one plug back in and shazam,,, I cut my planing speed,,, this has been discussed before.. They DEFINITELY work on through hull..