Professional advice on 8 PVS holes

[AllyFishing]

This question has always bugged me when setting up a new prop. And that is where to start adding plugs, back set of holes or front set and what size to use and should each hole have a certain size vs blocking off opposite holes etc.

I don't know if there is a general rule of thumb to go by or if it's specific to each bass boat brand. Of course some boats surface their props and others are buried.

Any help from professionals?

[21XDC]

I always suggest you start blocking exhaust ports farthest from the bow first. I also like to block them in pairs across from each other.

[Savage]

^^^This is how I do it also^^^

[AllyFishing]

ok so blocking off opposite holes on the outer holes closest to the blade tips? Do you start with solid opposite first? I have opposites outer hole (those closest to the blade tips) with small hole plugs and 2 opposite with large hole plugs closest to the gear case. I should move the ones closest to the gear case to the opposite holes of the outer ones? What effect is the exhaust gases have on each of the scenarios?

[AllyFishing]

Here's another question. I have a 29P hydro XOB with the flare ring trimmed a bit to help eliminate stern lift on my Allison; we don't need stern lift.. Why did that make this prop go from biting really well from first throttle til on plane to over revving and surging on hole shot? What are the properties affecting this and what changes should be made to the prop to get it hooked up right from the get go?

It is actually mimicking a stock ProMax prop on hole shot...hit the throttle, bow goes up while its going forward then as the bow begins to drop the prop over revs and surges til the bow is down and finally bites and goes. This is exaggerated with a second person sometimes taking more than 10 seconds to get going

[21XDC]

The flare is actually a diffuser... It directs the exhaust away from the tips of the blades. When shortened or removed, It allows exhaust gas to get on the tips of the blades and slip a lot.

Continue to block off holes until you get what you need... Leave front holes open, unless you still over vent.

[AllyFishing]

"Front holes open" as in the holes closest to the gear case, right?

Ok now I understand why it slips more now without the flare. Now my question is....what can be done to the prop/blades to stop that slipping? Or are you saying that keep adding plugs to outer holes to reduce slipping?? I did add a few more plugs but then it bogged down until it was able to hook up but then slipped

[21XDC]

Maybe add more cup to the trailing edge

[AllyFishing]

Mike are you familiar with the way a ProMax prop hole shots?

[21XDC]

Yes, I have owned many and still own one... I have had custom flares added, multi size cav rings made etc... Here are some pics.. I had dual pvs holes added later. Pics are from June 2013

[AllyFishing]

So how does that prop work now with the flare ring added? My most recent PM had a flare ring installed similar to yours and I could not free the bow up. I had that ring removed by a prop guy and he did something else to it to give it a better hole shot than what they experience stock. What ever he did it worked. Unfortunately that prop slung a blade recently.

I purchased a new one and this one hole shots great without all that over revving and sky high bow rise. Wonder if Merc did something different to them now? And I did notice that the barrel appears to be longer. I measured it and it is 7 1/16" long. What does your barrel measure on that prop?

[21XDC]

It’s still surged. I sold that prop years ago.

[AllyFishing]

Looking at your flare ring again I do notice that it's not as flared as the one I had installed on mine. Yours seems to be more of an extension than a lot of flare. That may be the difference. I know you've had experience with TXP OT4's too. that prop was always my all time favorite with my 225 ProMax on my Allison 2+2. I had gotten away from them and recently tried one again and I noticed it over revved too much with more bow rise than I remembered. And it just seems as thought the barrel looks shorter than what I remember. Any idea if they make them now with a shorter barrel?

[21XDC]

I have no idea. Now that Yamaha owns them, They can do anything they want.

[AllyFishing]

Another question Mike....the PM [prop I just purchased came with a ring to install on the hub. what will or does that do? I know it is to cut down on exhaust flow over the hub but what is the cause and affect?

[21XDC]

It makes it a full barrel prop as far as exhaust gas... Unlike a trophy that is an OT... Meaning "Over and Through" exhaust.

[AllyFishing]

So essentially it just sends the exhaust gases thru the hub rather than over and thru. Ok I knew that. But what, if any, affect does it have on hole shot and top speed? I've heard guys say that the ring will reduce speed on a prop with one added.

I understand that it accomplishes what adding plugs to holes does for hole shot but its more extreme and takes away from why a given prop has a smaller hub in the first place. CAn you (or someone) elaborate more on that?

Thanks!!

[21XDC]

I think it restricts exhaust flow and may show some speed loss on some set ups... I have not seen it personally.