Will venting a prop help hole shot during water sport?

[MercFan]

Hi guys,<br /><br />As you probably know my '70 Merc 1150 is a bit over propped at the moment. I can get a skier out of the water and pull a tube without hassles. But a 3 person worm is a hassle. I cannot get the worm to plane. I just can't get the rpm above 2500.<br /><br />Will venting my prop help a bit with this till get the bux together for a lower pitch prop?

 

[Laddies]

Re: Will venting a prop help hole shot during water sport?

It should help

 

[WillyBWright]

Re: Will venting a prop help hole shot during water sport?

It's worth a try. But ventilating doesn't work so well in pulling situations. Once the boat is on plane, the vents essentially close. It's sub-planing speeds where you'll have a problem because you need bite to pop up a skier. You'll be pushing foam until it planes. A water toy should be easier, so it may work for a toy. But I doubt it would help pulling out a skier.

 

[Clams Canino]

Re: Will venting a prop help hole shot during water sport?

Exactly... better to drop the pitch to where it belongs and be done with it - since you know you're overpropped.<br /><br />-W

 

[MercFan]

Re: Will venting a prop help hole shot during water sport?

The 17 is brand spanking new. Bought it last month for 300USD, which, once translated to South African rand is more than 1/10th of my salary!<br /><br />I would've just swopped it, but Dad sanded it on his first try out. So I'm a bit stuck for a while.<br /><br />But as I said, I can pull a skier without hassles, but that worm is bloody heavy!

 

[Laddies]

Re: Will venting a prop help hole shot during water sport?

In the USA we could take it to a prop shop and have a couple of inches of pitch knocked out of it

 

[emckelvy]

Re: Will venting a prop help hole shot during water sport?

?????? I've ventilated quite a few props for inlines and they've worked quite well for getting a better hole shot for slalom skiing etc. The key is to not get the hole too big, otherwise the prop'll over-ventilate.<br /><br />I recall one prop where we drilled very large holes (about 3/8") and put it on my brother's M1000 hung on a 17" Apollo runabout. It was like having an auto tranny or slipping clutch, spun up real tight and little grab. <br /><br />But 5/16" holes in my old 700E Dockbuster gave it a killer hole shot for skiing, on a 13.5" Sea King boat it'd just about rip your arms out! My skiing buddy did a beach start one time and took too many coils (these Dudes on the beach were laughing at our old rig, you see!), afterwards he said his head was spinning from the acceleration. BTW the Dudes weren't laughing so much after that!<br /><br />If you're going to drill, make sure you lay it out evenly on all (3) blades and start with only about 3/16" (4.7625MM) holes. Don't go more than 1/4" (6.35MM) as you may risk overventilating the prop. Of course you can always plug the holes afterwards, but that kinda defeats the purpose.<br /><br />I think Clams may have links to an illustration of how to lay out the holes???

 

[MercFan]

Re: Will venting a prop help hole shot during water sport?

Thanks Ed!<br /><br />I found the original OMC Service bulletin on DIY venting, with a drawing. It's basically 16mm x 16mm behind and above the exposed rib of the hub and above the leading edge looking at the boat from the right.<br /><br />Thanks for the size recommendations! I'll start out with a 4.5mm, test drive, go up 0.5mm, test again. If the change is pronounced I'll give the worm another go.

 

[Texasmark]

Re: Will venting a prop help hole shot during water sport?

My 2c<br /><br />Had one "ported" prop on an 17' Ranger with a 115 towered Merc. Having been my first prop of that sort, I was amazed at what it did for my hole shot with the skiier, beins the boat was a deep V padded and really liked to drag it's ***.....till it got hooked up.<br /><br />Mark

 

[Clams Canino]

Re: Will venting a prop help hole shot during water sport?

In a perfect world, what you're trying to achieve by venting a prop, is a situation where the venting allows the motor to spool up faster to hit its powerband and then as soon as it does, hook up and allow max bite. It can indeed be done.<br /><br />That said, because of the low tolerance the inlines have for being over-propped, I'd rather see a better hole shot appear by dropping a pitch or two.<br /><br />-W

 

[Motor Boater Bill]

Re: Will venting a prop help hole shot during water sport?

Would this same principle apply to a smaller motor (20 hp) on a 14 foot fishing boat? What I'm wondering is if this would solve the problem of the boat/motor/prop combination that works great for 2 fishermen but bogs down and won't plane with a third man on board.

 

[studlymandingo]

Re: Will venting a prop help hole shot during water sport?

I just put a Rapture prop on my 18' CenterConsole. It is a 14.25 X 21 on a 150 Mariner. The prop already has holes in it that are plugged, I have yet to take them out, but this is my next step. The 21 prop is right on the verge of being too much. I'm at 5100 WOT and the boat noses up a little coming out of the hole. I am interested to see what removing the plugs will do for the hole shot, I just got the boat, so I'm going to play around with things before tuning the prop back. The original 17 that was on the Mariner was definitely not enough, WOT wanted to go above 5600.

 

[MercFan]

Re: Will venting a prop help hole shot during water sport?

I'm very satified with the results from venting my prop. Acceleration is a lot better than it used to be. I can actually feel when the holes close and stop venting and the prop really starts biting. All in all a worthwhile mod for me.