"Venting" my prop good or bad?

[snowthrower]

I read an article about drilling a small 1/4" hole at the leading edge of the blades through the hub. The idea was to allow exhaust gases to pass through the onto the blades allowing it to slip a bit off the line. <br /><br />I have a 1967 seaswirl w/120hp merc I/O, and what I can only guess to be the original prop which is in good-far condition.<br /><br />My question is does this modification realy help out with hole shot? It's one of those things that just seems to easy.

 

[snowthrower]

Re: "Venting" my prop good or bad?

Here is the article that I was refering to: Venting your prop article <br /><br />I don't know if this helps but the theory seems good and my boat would fall under the hard to plain catogory.

 

[Scaaty]

Re: "Venting" my prop good or bad?

Could not get the article, but I remember some of us doing something similar back in the 70's when we all had fast boats with big pitch props and everybody leaning on the deck to get on plane......can't see how it would hurt (you can always get a new prop), and at speed will not matter. Go for it

 

[Chris1956]

Re: "Venting" my prop good or bad?

Snowthrower, The venting is used during holeshot to allow the prop to slip a bit, and achieve a higher RPM sooner, thereby getting into the powerband of the motor sooner. At high speed, the vent does not have any effect.<br />The question for you is whether your sterndrive will benefit from more prop slippage? I chose to plug the holes on my factory vented prop for my Mercruiser, since I did not think there was an advantage. Maybe I was incorrect. I did drill holes in the prop on my Merc. outboard, since I know it has a "peaky" powerband.

 

[snowthrower]

Re: "Venting" my prop good or bad?

OK I fixed the link, now you should be able to view the page. <br /><br />My boat does well at speed, I am just looking for as much "out of the hole" power as possible. The added RPM's would help for sure, I just didn't know if the whole thing was a load of bull or a valid modification.

 

[sangerwaker]

Re: "Venting" my prop good or bad?

Very valid modification. Why would so may props come with vent holes? Most of the Quicksilver, Turbo, Stilletto, etc. all come with factory vents. They act kind of like a stall speed converter on a drag car if you know what those are. My first stainless prop was a Ballistic that came with no vent holes. I took it back to the shop and had them put in 1/4" holes. Eventually, I increased the sizes to 5/16. Man, what a difference! My boat nearly jumped out of the water!<br /><br />Use the above link (thanks snowthrower). It should help locate where to drill the holes if you are going to do it yourself.<br /><br />EDIT: I forgot to mention, this will not add any performance improvement unless you have through hub exhaust. If your exhaust goes through the hull, don't bother venting the prop.

 

[JasonJ]

Re: "Venting" my prop good or bad?

I run a vented prop and the improvement over my non-vented prop was quite noticeable.

 

[snowthrower]

Re: "Venting" my prop good or bad?

Yes I have through hub exhaust. <br /><br />I think I will get the the drill out tonight. My boat does very well once it's on plain but it seems the motor is laboring more then it should (like if you took off in second gear in your car). I will start with a 1/4" hole and work my way up. <br /><br />We use the boat for towing and it just doesn't pull hard enough off the line.

 

[phatmanmike]

Re: "Venting" my prop good or bad?

DO NOT START WITH 1/4 INCH HOLES !!!!!!!!!!!<br /><br />start with 1/8 and go up from there, enlarging one hole at a time... and going up in size 1/16th at a time. the difference is quite large, so to have TOO big a hole would cause slipping in corners such as it did in my merc 115hp. i did mine at 5/16 and its fine untill i try to turn. just a thought<br /><br />measure twice, cut once<br /><br />mike

 

[RatFish]

Re: "Venting" my prop good or bad?

The Hustler Aluminum Props sold here on iboats are vented.

 

[snowthrower]

Re: "Venting" my prop good or bad?

DO NOT START WITH 1/4 INCH HOLES !!!!!!!!!!!<br />

OK, I was only going to start there because that is where the arcticle said to start. I think they state 6mm which is very close to 1/4.<br /><br />

The Hustler Aluminum Props sold here on iboats are vented. <br />

Thank you, but if I had the money to buy that I don't think I would have such an old boat.

 

[snowthrower]

Re: "Venting" my prop good or bad?

BTW thanks to all for the input. I will let you know how well/if it works. It may be some time before I can get her back out to the water but I can't wait and I have not even drilled it yet.

 

[snowthrower]

Re: "Venting" my prop good or bad?

Well, I no longer think I need to do this. I was cleaning my carb the other day, and was looking for any thing that might make more power. Low and behold I pulled the number one plug wire and got Zero drop in RPM's, checked the other three and got a noted drop in RPM. Well I pulled the plug out of number one and the center electrode was fried off. Call my dad ( who I bought it from ) cause he said he "just" put new plugs in it, well after some chit chat I find out that "Just" was two years ago. The whole time he owned the boat the tune up specs where way off. Any way I threw in four new plugs, rechecked my timing, point gap, and idle mix, then headed to the lake in the rain. <br /><br />Man was I suprised how well it ran, more top speed and I can now yank a skier out of the water in no time at all. I will hold off on the "venting" for now, but thanks huge for the advise!!!!