[Lex81]

Dear All,

This week i'll be trying out an Michiganwheel Apollo 4 blade 14x22 on my Mariah sx20/22 5.0mpi bravo 1. 1.65

It should be pretty fast on top and midrange. Talked to two people who were running this prop on the same set-up.

Persone 1:
- Speed 103KMH on the GPS but moderate holeshot. (Looks a bit high,a top of 103KMH or about 65MPH...)
Persone 2:
- Speed 94KMH or 58MPH on the GPS also moderate holeshot but good midrange and top. He was hitting top at about 5100RPM's.

I was debating... To improve holeshot in some situations, Mercury marine has the PVS system. Basicly some holes in the prop... variating the sizes with plastic plugs.... The theory with the exhaustgases passing by at the blades is clear and sounds logical.

Is this system also possible on other prop's? I mean, when I have a metal worker produce these same diameter holes with care and craftmanship on the same positions as with for example the Revolutiong 4 from mercury marine, so that also the plugs will fit. Wil this damage the structural power of the prop?

I just want it to be able to rev-up a litle faster at holeshot so to create maximum rpm's and possible torque...

Regards,

Lex

[mikeyt]

I have to admit that i know very little about the subject of drilling vent holes in props but there is quite a bit of info out there on other boating sites. Here's one to look at...

Propeller Venting

ps... i'm just a little dubious about the results of "Persone 1" I cant see anything like that being achieved with your Mariah and a 5.0.

[ColoradoDiablo]

Guess you could try this.

Propeller Venting

[ColoradoDiablo]

Your killin' me Mikey!

[gahooligan]

That seem like a lot of work just to ruin a perfectly good prop. Especially.when the correct prop and a set of trim.tabs will get the best performance. A 5.0 in a 20-22 ft boat is what it is. You are only going to get so much out of it and you can't have bottom and top end performance. It's one or the other or a compromise on both...

[mikeyt]

I dunno but from what i've read there is evidence that drilling the props like they suggest can help in some situations. And, i know that a number of new props already have holes like this that are filled with plugs that can be removed. I also know it used to be a trick used by the outboard bass boat guys to get a little more hole shot yet retain their top speeds. It has no effect on the middle to upper rpm range though. And its kind of questionable as to whether it will work in the OP's situation. And yes, that's the limit on what i know....

[Motoxxx43]

As it was described to me at the prop shop customers say its like putting headers on the motor. Whatever that means...

Sent from my DROID RAZR HD using Tapatalk

[Lex81]

Thank you guys for the info! And thank you for the links!! All seems pretty clear. As far as I can see, if done correct it either has no effect or a good effect..

Motoxxx43: Not sure what you mean by "putting headers on a motor"... is that the same meaning as an improvement? Tried to google it but don't have a clue. In car engines it has to do with the exhaust... Sorry, not a native English speaker.

[Lex81]

So, I found my prop and so far from mid to top I am appy with it! I reach 87KM's at 5100 RPM's. It is a michigan wheel Apollo 4 blade 14x22.

Now back to the venting.

When I'm dead in the water and give full throttle, the holeshot is not bad but I think it could be a litle better. The engine rev's up to 3000 RPM's. Isn't that a litle low?

I tried a Revolution 4 ones and with 4 closed ventplugs the holoeshot was "not acceptable" and reached about 2900 rpm's at full throttle from still stand. I removed 2 plugs and it reved significantly more and the holeshot was a lot better!! I believe it reved up to about 3200RPM's.

What to do,... What would be a good RPM range to hit when giving full throttle to get in plane? Would it be around 3500? 4000? I could start drilling with small holes, say 2 4mm holes to start with. But what RPM's should I aim for?



Best regards,