Drilling Hole to Add Vents To Non-Vented Propellers

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Author Topic:   Drilling Hole to Add Vents To Non-Vented Propellers

R T M posted 01-01-2010 06:52 AM ET (US)
This post was copied from another boating site. This is a topic I know nothing about but the info could be useful as I need all the [acceleration from a standing start] I can find in my 25-HP Mercury-brand Tohatsu-made 4 stroke powered 13 footer.
How [do] the three 7/32-inch drill holes on the propeller help [?]
I was reading a [Seloc] repair manual, and it stated that...drilling three 7/32-inch holes, one behind the base of each blade of the propeller at 5/8-inch back from the inner lip would help exhaust gasses to bleed onto the propeller blades causing controlled ventilation during the acceleration period; this action will allow the motor to turn at a higher [engine speed] under acceleration providing more power to plane the boat faster.
Has anyone [tried] [drilling holes in a propeller hub to add vents to a non-vented propeller]? Does [drilling holes in a propeller hub to add vents to a non-vented propeller] work [to improve acceleration from a standing start]? I'm almost going for it but not 100% sure YET!!
rich/Binkie

Russ 13 posted 01-01-2010 10:52 AM ET (US)
Yes I have used it on several Whalers. It works. I have a 13-foot boat [with] a Yamaha 40 two-cycle engine spinning a 15p stainless Stilletto. It made the [acceleration from a standing start] the same as running a 13p--I tried both props before having the 15p vented. Placement of the holes is important. I would start with small holes and run the boat. You can always enlarge them, if you need more slip. Found out about the vent idea many years ago when I was searching for a good stainless prop for an outboard powered ski boat, needed a good [acceleration from a standing start] for wakeboarding. Mercury had a prop called the [LASER II], that was made with vents. Great [acceleration from a standing start] and no loss in top speed.
contender posted 01-01-2010 03:39 PM ET (US)
Russ I would like to see some pictures if possible, Thanks
Russ 13 posted 01-05-2010 08:11 PM ET (US)
I don't have any prop photos here. But a shot from Mercury or Stilletto stainless catalog, would show the general hole placement. Some of the Mercury props use a rectangularly shaped hole that can be filled with a rubber plug, if you don't want to run it vented.
[Later] Checked out Mercury's outboard web site. In their propeller section they show a prop called FURY. The vent holes are shown in detail there. One nice looking stainless prop, probably expensive. Holes, Holes. Good for the cheese, good for the propeller. Bad for the boat.
jimh posted 01-10-2010 01:37 PM ET (US)
I have not tried drilling holes in the hub of a non-vented propeller to improve acceleration from a standing start. I have observed that on some non-vented propellers I see circular reliefs in the casting in the hub area where a vent hole could be located, and I make the inference from the presence of these circular reliefs on the the propeller hub casting that one could drill holes there for the purpose of venting the propeller. Whether or not that would improve the acceleration from a standing start would have to be determined by testing.
Russ 13 posted 01-10-2010 03:27 PM ET (US)
I have used props with holes on many Whalers.
(Not to be confused with Whalers with too many holes,a different topic, covered in the repair section)
Always have experianced a LARGE IMPROVEMENT with hole shot.
No bad side effects, no loss in speed, no loss in grip when up on a plane, no loss in grip in rough water.
I would reccommend your local propeller repair shop, or
Burris Propeller in Cape Coral, Fl. (239-772-3222)
They have vented several props for me, all with great results. And it is not very expensive, for small props.
For large props, I would look for one manufactured that way, many larger stainless props are available vented.
It roughly improves the hole shot, equal to running one prop size smaller, Ie 15p. to 13p. For hole shot, with no reduction in top speed.
Russ
R T M posted 01-10-2010 05:07 PM ET (US)
If this winterlike below freezing weather leaves Central Florida, by next weekend, I will drill some 1/8" holes at the required places in the prop of my 13 footer, powered by a '08 25hp 4 stroke Merc/Tohatsu, and run some tests at the AOMCI meet next Saturday 1/16. and report back. I`ll keep opening the holes(making them larger) and see if acceleration improves. This boat-motor-prop combo suffers from sloow holeshot, and probably needs less pitch. (using 11" now), although top end speed and rpm are normal, The motor runns on a 6" setback jack plate and the cav. plate is slightly above the surface at "high" speed.
rich/Binkie
Russ 13 posted 01-10-2010 11:04 PM ET (US)
Yes, the weather has not been good for boating.
I believe the holes in my small prop, for the 50hp. are
3/8 inch. in size, one hole at the base of each blade.
I think you will be please with the results.
R T M posted 01-11-2010 07:12 AM ET (US)
Thanks Russ, I`ll start with 1/4" holes instead of 1/8" and work up. Plan on drilling the holes today, but right now it`s 20 degrees in Spring Hill, 40 miles north of Tampa. Hard to believe, must be a record. I lived in Ft. Myers for 30 years and saw temps at 29 degrees, once back in the 70's.
rich/Binkie
contender posted 01-12-2010 09:04 PM ET (US)
I would drill a large hole and thread it, then you can try different size threaded plugs with different size holes in them to find the correct hole size you need. If it does not work you can plug the hole with a solid plug...
15ft90hp posted 01-13-2010 12:40 AM ET (US)
Use these...
http://sites.mercurymarine.com/portal/page?_pageid=126,50050,126_50060&_dad=portal&_schema=PORTAL

Buy them here...
http://rainboat.com/performanceventplugs.aspx
Russ 13 posted 01-15-2010 07:16 AM ET (US)
R T M any progress with the "holey prop"??
R T M posted 01-18-2010 12:50 PM ET (US)
Hope the weather improves soon, so I can get out and do some testing. Its either to cold or too windy.
rich/Binkie
Russ 13 posted 01-19-2010 03:07 PM ET (US)
AHH yes, the fun of winter........but no snow!
Let me know how your testing goes.
R T M posted 01-21-2010 01:01 PM ET (US)
I brought a prop in off my race boat yesterday to get reworked, and I mentioned venting to my prop-guy, and he said that venting won`t help a 25hp motor, and if I did drill holes they should be angled inward toward the exhaust. I already drilled the holes, and I think I will re drill them on an angle like he suggested. We will see if he is right.
rich/Binkie
L H G posted 01-21-2010 01:57 PM ET (US)
Mercury makes no vented props using their patented PVS System of interchangable plugs, for engines less than 75 HP using a 4-1/4" diameter hub, and generally not for boat speeds less than 40 MPH. Nor do they use them on any aluminum props, or the Vengeance line of SS props. So what does that tell you?
Evidently, this means the performance/prop experts at Mercury are telling us for engines 60 Hp and less, venting makes no sense.
Generally, vents are only used in agressively raked props that give high top end, but where the design would suffer in acceleration. Props like the Laser II, Trophy Plus, Tempest Plus, Revolution 4 and higher pitched Mirage Plus, can all benefit from venting.
Russ 13 posted 01-23-2010 11:18 PM ET (US)
Well for all the " experts " who have not tried venting.
I had a stainless stilletto prop vented for a 50 hp.
And it made a HUGE improvement in the boats hole shot.
The principle is the same, reguardless of de HP.
So far 6 props on 6 different boats: All vented--All better
hole shot, with NO negative side effects....
IT'S A BIRD, IT'S A PLANE, IT'S BETTER THAN
SHAM-WOW......UNBELIEVABLE!! ONLY $ 39.95 plus S&H.
R T M posted 01-24-2010 07:14 AM ET (US)
Russ, I agree with you, its logical to assume that a small amount of exhaust exiting from behind the blade will cause cavitation, and make the prop spin faster on acceleration. the question is how big a hole for each setup. I think this can only be determined by testing, and I would tend to agree with you that it would help holeshots on just about all boats.
rich/Binkie
Russ 13 posted 01-24-2010 11:20 PM ET (US)
I measured the prop on the 50 HP. the three holes are 3/8 inch in diameter. One at the base of each blade.
I agree, a smaller prop may require smaller holes, to slip
properly. Let me know how your testing goes.
footsie posted 02-05-2010 10:48 AM ET (US)
RTM, I am very interested in the test results of your drilling experience on your prop. What size holes and the angle of drilling are of specific interest as are the performance changes. Did you do it to your aluminum 11" pitch prop?
I am considering implementing this process on 15" SS props for my 30 hp Nissan that is 5.5" setback on my 11' Super Sport.
R T M posted 02-05-2010 12:27 PM ET (US)
Footsie, the weather here on the west coast of Central Fl. is not what I would want for any kind of boating, cold, rainy, or windy,or all of the 3 since December. Hoping to get the opportunity to test my vented 11" prop at some point. My prop guy told me not to expect any difference at all. I drilled 1/4" holes at the base of each blade, and angled the holes in as much as possible, not much. Prop guy also sold me a 9" prop, at about half price, that was tested once, so I`ll try that one too, but I don`t expect to have to vent the 9" prop.
rich/Binkie
footsie posted 03-30-2010 05:43 PM ET (US)
RTM Surely It's been warm enough in Florida to determine if your "prop guy" was right or wrong..???? What's the status?
jimh posted 03-30-2010 10:31 PM ET (US)
R T M won't be answering you here. He has been banned. He was banned because he repeatedly registered with multiple user names, and repeatedly posted offensive material. He posted what I consider to be the most offensive and inexcusably poor taste article in the history of this website, which resulted in my irrevocable decision to ban him from further participation. The few on-topic boating articles he contributed were insufficient to balance his otherwise unwelcome behavior.
Russ 13 posted 04-01-2010 12:23 AM ET (US)
Well I guess my "holey" pun should have been thought out
by RTM. I don't get the negative bashing, when we are
talking about the fun hobby of recreational boating.
.....
To those interrested, most small boats running the correct
pitch propeller for their engine/horsepower combination,
will benefit from exhaust hub vent holes.
I recommend getting advice on this from your local prop shop.
pcrussell50 posted 04-03-2010 01:07 AM ET (US)
OMC has a line of stainless steel props called Rakers. They have ventilation holes already drilled in them. They are highly regarded in the "fastboat" community, for the same reasons put forth here... namely, good acceleration from a standstill, with enough pitch to allow for high speed.
OMC's own site, for refernce:
http://www.evinrude-parts.com/raker_propeller_evinrude.html
-Peter

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Author	Topic: Drilling Hole to Add Vents To Non-Vented Propellers
R T M	posted 01-01-2010 06:52 AM ET (US) This post was copied from another boating site. This is a topic I know nothing about but the info could be useful as I need all the [acceleration from a standing start] I can find in my 25-HP Mercury-brand Tohatsu-made 4 stroke powered 13 footer. How [do] the three 7/32-inch drill holes on the propeller help [?] I was reading a [Seloc] repair manual, and it stated that...drilling three 7/32-inch holes, one behind the base of each blade of the propeller at 5/8-inch back from the inner lip would help exhaust gasses to bleed onto the propeller blades causing controlled ventilation during the acceleration period; this action will allow the motor to turn at a higher [engine speed] under acceleration providing more power to plane the boat faster. Has anyone [tried] [drilling holes in a propeller hub to add vents to a non-vented propeller]? Does [drilling holes in a propeller hub to add vents to a non-vented propeller] work [to improve acceleration from a standing start]? I'm almost going for it but not 100% sure YET!! rich/Binkie
Russ 13	posted 01-01-2010 10:52 AM ET (US) Yes I have used it on several Whalers. It works. I have a 13-foot boat [with] a Yamaha 40 two-cycle engine spinning a 15p stainless Stilletto. It made the [acceleration from a standing start] the same as running a 13p--I tried both props before having the 15p vented. Placement of the holes is important. I would start with small holes and run the boat. You can always enlarge them, if you need more slip. Found out about the vent idea many years ago when I was searching for a good stainless prop for an outboard powered ski boat, needed a good [acceleration from a standing start] for wakeboarding. Mercury had a prop called the [LASER II], that was made with vents. Great [acceleration from a standing start] and no loss in top speed.
contender	posted 01-01-2010 03:39 PM ET (US) Russ I would like to see some pictures if possible, Thanks
Russ 13	posted 01-05-2010 08:11 PM ET (US) I don't have any prop photos here. But a shot from Mercury or Stilletto stainless catalog, would show the general hole placement. Some of the Mercury props use a rectangularly shaped hole that can be filled with a rubber plug, if you don't want to run it vented. [Later] Checked out Mercury's outboard web site. In their propeller section they show a prop called FURY. The vent holes are shown in detail there. One nice looking stainless prop, probably expensive. Holes, Holes. Good for the cheese, good for the propeller. Bad for the boat.
jimh	posted 01-10-2010 01:37 PM ET (US) I have not tried drilling holes in the hub of a non-vented propeller to improve acceleration from a standing start. I have observed that on some non-vented propellers I see circular reliefs in the casting in the hub area where a vent hole could be located, and I make the inference from the presence of these circular reliefs on the the propeller hub casting that one could drill holes there for the purpose of venting the propeller. Whether or not that would improve the acceleration from a standing start would have to be determined by testing.
Russ 13	posted 01-10-2010 03:27 PM ET (US) I have used props with holes on many Whalers. (Not to be confused with Whalers with too many holes,a different topic, covered in the repair section) Always have experianced a LARGE IMPROVEMENT with hole shot. No bad side effects, no loss in speed, no loss in grip when up on a plane, no loss in grip in rough water. I would reccommend your local propeller repair shop, or Burris Propeller in Cape Coral, Fl. (239-772-3222) They have vented several props for me, all with great results. And it is not very expensive, for small props. For large props, I would look for one manufactured that way, many larger stainless props are available vented. It roughly improves the hole shot, equal to running one prop size smaller, Ie 15p. to 13p. For hole shot, with no reduction in top speed. Russ
R T M	posted 01-10-2010 05:07 PM ET (US) If this winterlike below freezing weather leaves Central Florida, by next weekend, I will drill some 1/8" holes at the required places in the prop of my 13 footer, powered by a '08 25hp 4 stroke Merc/Tohatsu, and run some tests at the AOMCI meet next Saturday 1/16. and report back. I`ll keep opening the holes(making them larger) and see if acceleration improves. This boat-motor-prop combo suffers from sloow holeshot, and probably needs less pitch. (using 11" now), although top end speed and rpm are normal, The motor runns on a 6" setback jack plate and the cav. plate is slightly above the surface at "high" speed. rich/Binkie
Russ 13	posted 01-10-2010 11:04 PM ET (US) Yes, the weather has not been good for boating. I believe the holes in my small prop, for the 50hp. are 3/8 inch. in size, one hole at the base of each blade. I think you will be please with the results.
R T M	posted 01-11-2010 07:12 AM ET (US) Thanks Russ, I`ll start with 1/4" holes instead of 1/8" and work up. Plan on drilling the holes today, but right now it`s 20 degrees in Spring Hill, 40 miles north of Tampa. Hard to believe, must be a record. I lived in Ft. Myers for 30 years and saw temps at 29 degrees, once back in the 70's. rich/Binkie
contender	posted 01-12-2010 09:04 PM ET (US) I would drill a large hole and thread it, then you can try different size threaded plugs with different size holes in them to find the correct hole size you need. If it does not work you can plug the hole with a solid plug...
15ft90hp	posted 01-13-2010 12:40 AM ET (US) Use these... http://sites.mercurymarine.com/portal/page?_pageid=126,50050,126_50060&_dad=portal&_schema=PORTAL Buy them here... http://rainboat.com/performanceventplugs.aspx
Russ 13	posted 01-15-2010 07:16 AM ET (US) R T M any progress with the "holey prop"??
R T M	posted 01-18-2010 12:50 PM ET (US) Hope the weather improves soon, so I can get out and do some testing. Its either to cold or too windy. rich/Binkie
Russ 13	posted 01-19-2010 03:07 PM ET (US) AHH yes, the fun of winter........but no snow! Let me know how your testing goes.
R T M	posted 01-21-2010 01:01 PM ET (US) I brought a prop in off my race boat yesterday to get reworked, and I mentioned venting to my prop-guy, and he said that venting won`t help a 25hp motor, and if I did drill holes they should be angled inward toward the exhaust. I already drilled the holes, and I think I will re drill them on an angle like he suggested. We will see if he is right. rich/Binkie
L H G	posted 01-21-2010 01:57 PM ET (US) Mercury makes no vented props using their patented PVS System of interchangable plugs, for engines less than 75 HP using a 4-1/4" diameter hub, and generally not for boat speeds less than 40 MPH. Nor do they use them on any aluminum props, or the Vengeance line of SS props. So what does that tell you? Evidently, this means the performance/prop experts at Mercury are telling us for engines 60 Hp and less, venting makes no sense. Generally, vents are only used in agressively raked props that give high top end, but where the design would suffer in acceleration. Props like the Laser II, Trophy Plus, Tempest Plus, Revolution 4 and higher pitched Mirage Plus, can all benefit from venting.
Russ 13	posted 01-23-2010 11:18 PM ET (US) Well for all the " experts " who have not tried venting. I had a stainless stilletto prop vented for a 50 hp. And it made a HUGE improvement in the boats hole shot. The principle is the same, reguardless of de HP. So far 6 props on 6 different boats: All vented--All better hole shot, with NO negative side effects.... IT'S A BIRD, IT'S A PLANE, IT'S BETTER THAN SHAM-WOW......UNBELIEVABLE!! ONLY $ 39.95 plus S&H.
R T M	posted 01-24-2010 07:14 AM ET (US) Russ, I agree with you, its logical to assume that a small amount of exhaust exiting from behind the blade will cause cavitation, and make the prop spin faster on acceleration. the question is how big a hole for each setup. I think this can only be determined by testing, and I would tend to agree with you that it would help holeshots on just about all boats. rich/Binkie
Russ 13	posted 01-24-2010 11:20 PM ET (US) I measured the prop on the 50 HP. the three holes are 3/8 inch in diameter. One at the base of each blade. I agree, a smaller prop may require smaller holes, to slip properly. Let me know how your testing goes.
footsie	posted 02-05-2010 10:48 AM ET (US) RTM, I am very interested in the test results of your drilling experience on your prop. What size holes and the angle of drilling are of specific interest as are the performance changes. Did you do it to your aluminum 11" pitch prop? I am considering implementing this process on 15" SS props for my 30 hp Nissan that is 5.5" setback on my 11' Super Sport.
R T M	posted 02-05-2010 12:27 PM ET (US) Footsie, the weather here on the west coast of Central Fl. is not what I would want for any kind of boating, cold, rainy, or windy,or all of the 3 since December. Hoping to get the opportunity to test my vented 11" prop at some point. My prop guy told me not to expect any difference at all. I drilled 1/4" holes at the base of each blade, and angled the holes in as much as possible, not much. Prop guy also sold me a 9" prop, at about half price, that was tested once, so I`ll try that one too, but I don`t expect to have to vent the 9" prop. rich/Binkie
footsie	posted 03-30-2010 05:43 PM ET (US) RTM Surely It's been warm enough in Florida to determine if your "prop guy" was right or wrong..???? What's the status?
jimh	posted 03-30-2010 10:31 PM ET (US) R T M won't be answering you here. He has been banned. He was banned because he repeatedly registered with multiple user names, and repeatedly posted offensive material. He posted what I consider to be the most offensive and inexcusably poor taste article in the history of this website, which resulted in my irrevocable decision to ban him from further participation. The few on-topic boating articles he contributed were insufficient to balance his otherwise unwelcome behavior.
Russ 13	posted 04-01-2010 12:23 AM ET (US) Well I guess my "holey" pun should have been thought out by RTM. I don't get the negative bashing, when we are talking about the fun hobby of recreational boating. ..... To those interrested, most small boats running the correct pitch propeller for their engine/horsepower combination, will benefit from exhaust hub vent holes. I recommend getting advice on this from your local prop shop.
pcrussell50	posted 04-03-2010 01:07 AM ET (US) OMC has a line of stainless steel props called Rakers. They have ventilation holes already drilled in them. They are highly regarded in the "fastboat" community, for the same reasons put forth here... namely, good acceleration from a standstill, with enough pitch to allow for high speed. OMC's own site, for refernce: http://www.evinrude-parts.com/raker_propeller_evinrude.html -Peter