Should I drill holes in my prop?

[Nick1818]

Just wondering if it pays to drill holes in the prop and where would I drill them?

 

[Texasmark]

Re: Should I drill holes in my prop?

dhadley has a diagram. You only use them if you have a lard arse boat that you want to get outta da hole fast but don't want to affect the top end by using a lower pitched prop. Or if you want to get those skiiers up faster without affecting anything else.

Size matters also.

If you have a light boat you don't want/need them.

Mark

 

[Ron G]

Re: Should I drill holes in my prop?

nick give us the run down on your boat and motor.type of boat,size and year of motor what prop your running now and wot numbers and what ya trying to achieve.

 

[Nick1818]

Re: Should I drill holes in my prop?

I have a 79 Starcraft Questar 170 fiberglass 17ft with a 79 Johnson Javelin 100hp. 13.5x15p prop. 5400 rpm 40mph +/-. I would like to get more hole shot not so much for me but my friends when we are out wakeboarding. It pops me out no problem but takes 15 seconds for guys over 200 pounds. I built a 5 ft ski bar, made a big difference but still looking for more answers to get me through the year. Also my engine being a '79, What would the actual hp be? I heard the rated them different back then.

 

[Ron G]

Re: Should I drill holes in my prop?

this from another member here on ib.

 

[tmh]

Re: Should I drill holes in my prop?

OK, something I don't get about drilling holes in props..... if there is no downside, and the hole shot is improved, why don't they come with holes in them? Centuries of prop design and they don't have holes "stock"...or DO some?

Any downside?

Thanks

 

[kenmyfam]

Re: Should I drill holes in my prop?

That is a very good question. I look forward to an answer.

 

[crunch]

Re: Should I drill holes in my prop?

this from another member here on ib.

OK, I'll bite...what is it?

 

[imported_HammerHead1]

Re: Should I drill holes in my prop?

Traditionally, props vent exhaust through the center of the hub to ensure undisturbed water delivery to the blades. Vented props allow a limited amount of exhaust to pass into the blade area through holes drilled in the outer hub. This aerates the water and reduces drag resistance on the blades. As the boat accelerates, the vented prop turns easier, allowing engine rpm to rise more rapidly for quicker hole shots. This means that vented props are hole-shot specialists. Once a boat is planing, water passes over the vent holes so fast that the holes effectively become ineffective and only minimal exhaust slips through. With the blades operating in solid, non-aerated water, there is no effect on top-end speed.

hope this helps
T.A.

 

[crunch]

Re: Should I drill holes in my prop?

So the diagram shows a 5/8 hole at the leading edge of each blade?... Do you have to take it to a prop shop or can you DIYS with a drill press?

Thanx TA, I was thinking holes in the blade itself which would cause cavitation... a no-no as far as I know 8)

There are 4 spellings of 2....
To,Too, Two...., and Tu Tu.

 

[imported_HammerHead1]

Re: Should I drill holes in my prop?

study the diagram above, start with a 3/8" hole, looking @ the prop from the gear case side 90 degrees from the center line and 5/8" in from the prop step, I like to trail chamfer, it has suprizing results with some props, but we can get into that later, first and formost be sure your set up is correct before modifying your prop...

T.A.

 

[crunch]

Re: Should I drill holes in my prop?

LOL... I'm still trying ( in another thread) to find out where the numbers are ( dia. and pitch) on a prop.

By the time I'll be worried about hole shot advantage from drilling holes in my prop hub... well, I just can't imagine 8)

Call it idle curiosity... interesting concept, but not conducive to puttering around on the lake with the family, but very interesting concept...

Thanx again,

 

[Ron G]

Re: Should I drill holes in my prop?

TA is right on there.and most stainless props do come with holes in them and also you can start plugging the holes to even finner tune it.

 

[Crownie2]

Re: Should I drill holes in my prop?

I think the vent holes have become more popular in recent years for two reasons:

1) High HP outboards often make a lot of HP at higher RPM's but not very much at low RPM's. The vents help the engine spin up quicker and this creates more available HP at lower speeds.

2) More recent bass boats are getting heavier and heavier and need a little help in the acceleration department. For the reason stated above the vents help bass boats a lot.

Note: the vents don't help nearly as much on a I/O because the engine already produces good torque at low RPM's. In fact, too big a hole will create so much slip that acceleration can actually be worse. For this reason, vent holes have to be approached very carefully on an I/O.

Bob

 

[Texasmark]

Re: Should I drill holes in my prop?

Answer to question as to why this late in the world of boating? Maybe guys like OEM racing teams, Kenny, dhadley and co, and guys like BAM are always diddling with their setups to get more out of it. Maybe prior to now, they just didn't think of that trick......but baby, it sure makes a lot of sense.

Since HP is tied to rpm's, if you can get your rpm's up, your hp is up and hp is what turns props.

Thru hub props didn't come out till about '65 so that's not that big a part of boats from day 1 and venting does nothing for you if your prop is not flow thru.

Totally agree on boats getting heavier.

Know that if you are a basser in a tournament, gotta have both fast hole and fast WOT if you want to have a chance at winning.....who doesn't? Hard to get both with one prop.......but can do with ports in it.

And for skiing, can't beat it if you want a lot of top end when not skiing and don't want to be changing props all the time. BTDT

My 2c,

Mark

 

[cgBosun3]

Re: Should I drill holes in my prop?

Just be careful about hole size...a prop shop put the vent holes in my wheel before I bought the rig to improve acceleration with a big pitch (24" on a 20 ft boat) for top end. The holes are too big; the prop just ventilates in any chop at all and slips so much it couldn't push the boat out of the hole unless its just me in it! It's great going nearly 70mph with only 150hp, but not if it takes a mile to get on top! My advice is start small; hard to put stainless steel back in a hole!!

 

[tommays]

Re: Should I drill holes in my prop?

Well i can tell you that a 1/4" hole does a LOT and is a good place to start


Tommays

 

[tmh]

Re: Should I drill holes in my prop?

Is this technigue only applicable to SS props or can it be done with aluminum?

I HATE giving up much top end but certainly need hole shot for skiing/tubing, etc. I'm willing to spend to have the vent holes put in, and would pay for the SS prop also, but I'm not comfortable with SS due to many, many folks saying it can ruin your gears, etc. Not sure if THAT is legit as some say it's hogwash, but I'm afraid to risk it. My boat isn't worth the fix job if that problem occured!

Thanks.

 

[Nick1818]

Re: Should I drill holes in my prop?

Thanks guys for all the input. My prop is aluminum. I am wondering the same thing as tmh, Does it only work with SS? I can't figure out why it wouldn't work for aluminum also.

 

[vipzach]

Re: Should I drill holes in my prop?

Tommays has posted pics before of his prop that he drilled, if I remember correctly, it was aluminum. I see no reason for not trying it on aluminum. Start with the 1/4 inch, study the diagram and enjoy your improved hole shot.