Porting the prop

[the rebel]

I have heard this phrase used before but didn't know what it meant. I looked at a ported prop today and it appeared to have 3/8-7/16 dia. holes drilled into the prop behind the blades. I didn't have my calipers with me to measure them. Is the location of these holes(ports) critical? They look to be about 5/8-3/4in. from the edge of the prop(next to the foot) and the same from the edge of the back of the blade. What exactly does this do that would allow the engine to rev quicker? Is it letting more exhaust out or does it actually allow the prop to pull water into these ports for an anti cavitation effect? <br />Preciate it guys. BWJ

 

[papasmurf]

Re: Porting the prop

It allows exhaust gasses out from the prop, and causes a controlled ventilation during acceleration, which allows the boat to plane faster. The placement is very critical and the boat and motor must be throughly checked before drilling these holes..

 

[the rebel]

Re: Porting the prop

Hi papasmurf, do you have any specs or dimensions as to where these ports are to be drilled? I am a toolmaker by trade and the machine work won't be a problem. What exactly needs to be checked on the boat and motor before drilling these holes? Thanks for the info. BWJ

 

[the rebel]

Re: Porting the prop

^

 

[papasmurf]

Re: Porting the prop

There is a service bulletin on this matter. I'll see if I can locate it. An e-mail address would help.

 

[umblecumbuz]

Re: Porting the prop

Hi BWJ,<br /><br />Guess, like most of us, you've experienced prop venting before now, huh? - Where the engine races and the prop loses grip?<br /><br />That's what these holes do. They allow CONTROLLED ventilation, which causes the motor to rise up the rev scale more quickly. Faster the revs, the greater power the motor develops. This spins the prop faster on take-off, giving more power for quicker hole shot.<br /><br />The ventilation effect at higher boat speeds is minimal and doesn't lose performance.<br /><br />And yep - the hole size and position is important for the effect to work. I've got an OMC bulletin on this, which I'm searching for. When I find it I'll post back unless some expert beats me to it.<br /><br />I'm not a prop guru, but I have experimented by both cupping (and uncupping) my own props and drilling them (and then plugging them!). The system worked for me, and doing it my own way has taught me a lot.

 

[willamettejeff]

Re: Porting the prop

BWJ, you might want to do a search on this subject as I remember there being a lengthy and very informative discussion on it in the not to distant past. In the meantime though if you decide to do this, you will want to start with small holes about 1/4 to 5/16 inch and work your way up. As I remember, you probably don't want to go over 3/8 to 7/16 as you will kill your holeshot and noticably lose speed on the top end as various members discovered. I myself chose to go with Turningpoint's Hustler propellers that include factory designed ventilation holes. Holeshot and overall performance has been great with these props and I just don't seem to be able to wear the finish off, so they stay nice looking as well.

 

[bubbakat]

Re: Porting the prop

 

[umblecumbuz]

Re: Porting the prop

That's the one! Bubbakat!<br /><br />I drilled my holes oversize, then made up a bunch of plugs. I then drilled the plugs in threes, with different-sized holes, and experimented. I also drilled holes at differing angles, to see what difference - if any - the angle made.<br /><br />Eventually I got a set that suited my rig.

 

[the rebel]

Re: Porting the prop

10-4. Absolutely great. This is exactly what I am looking for. Thank you for bringing this to my attention guys. Bubbakat thanks for posting, is there more on that bulletin, or where can I locate these bulletins?<br /><br /> If you go back to my original post, my dimensions on hole placement were right on the money. Not bad for just eyeballing a prop on the shelf. Hehe. Man, now I got something to play with, awwh man this is great . Thanks everyone. BWJ.

 

[bubbakat]

Re: Porting the prop

Post your e-mail addy and I'll send you all I have on this.

 

[the rebel]

Re: Porting the prop

Originally posted by bubbakat:<br /> Post your e-mail addy and I'll send you all I have on this.

Thanks, but I would rather not post that on an open forum. I have not been able to send PMs for some reason. I am checking in to that now. Don't give up on me. I will PM you when I get it fixed. BWJ.

 

[Basscat 1]

Re: Porting the prop

Hey bubbakat, could you email me too? I am interested in this too. My email is: ************<br />It sounds like a solution to my semi-slow planing boat.<br />I have access to a machine shop, and could get it done if I decided to try it.<br />Thanks.

 

[bubbakat]

Re: Porting the prop

Basscat ck that addy again it came back to me.<br />Give it awhile I think I might have messed up while doing it. I have redone and resent<br /><br />BWJ e-mail me at<br /><br />I can always bounce ant unwanted mail that is not on my list and AI will leave a hole for you to get thru.

 

[Basscat 1]

Re: Porting the prop

Thanks bubbakat. Just to verify, I got two attatchments.

 

[bubbakat]

Re: Porting the prop

yep that would be it.

 

[the rebel]

Re: Porting the prop

Originally posted by bubbakat:<br /> Basscat ck that addy again it came back to me.<br />Give it awhile I think I might have messed up while doing it. I have redone and resent<br /><br />BWJ e-mail me at<br /><br />I can always bounce ant unwanted mail that is not on my list and AI will leave a hole for you to get thru.

email sent. Did you get it bubbakat?

 

[bubbakat]

Re: Porting the prop

YEP sure did.<br />Did I send you the bullityen or did I miss you.<br />Man I am ghetting forgetful

 

[the rebel]

Re: Porting the prop

Originally posted by bubbakat:<br /> YEP sure did.<br />Did I send you the bullityen or did I miss you.<br />Man I am ghetting forgetful

Nope, never got it. You musta missed me. BWJ

 

[bubbakat]

Re: Porting the prop

BWJ you have mail<br /><br />sorry about that man.