When starting out with a new prop. If you have 8 holes where do you start plugging them? Do you start plugging holes next to the gear case or away from the case. I have always heard plug the ones next to the case first and work out but I was just told that's not correct by the guys that know. What's your thoughts?
It does change how the prop vents across the blades.
I have always started plugging the ones farthest from the case first. Not sure what the official rule of thumb is but mine launches pretty well.
Jay McDaniel
2003 Allison XB21 BasSport Elite 2+2
2019 Mercury Racing 300R
Interesting I have done the opposite but may change now
The holes farther from the case ventilate the prop more than the closer ones, if that helps.Originally Posted by hooken203
Yes it does thanks Lee. I think where my thoughts come from on this is the days where we only had 4 holes they obviously went in next to the case. So I just stuck with that.
So I put 4 large hole plugs in the holes furthest from the gear case. Now have a fair hole shot with RPM jump to 3500. I would like it to closer to 4000. But now I get a bad blow out when the boat is about half way up. Vibrates the boat real bad and the engine surges until it's all the way up and it hooks up and goes. Adding more plugs is the simple answer but I don't want to lower my initial punch RPM but I want to stop the blow out. Running the engine lower at take off doesn't seem to help. Suggestion?
Have you tried your hole shots with the engine 3/4" over pad?
Yes even and up the blow out is worse. What I did was start out all the way down with the plate moved it 1/2 each time until I was 2 inches above.
If you remove more plugs (add venting) it should spool up higher, not sure what it will do to blow out. It may also help with the surging. I run hydro q4xob's with 4ea 1.25 x 1.125 slots and 4 pvs holes/no plugs and have also removed the 3/4" flair ring. Spools up to 5000 rpm and goes. I know the hulls are different but that's what I ended up doing.
If I did that Strokerdean my boat wouldn't get on plane. When I had just two solid plugs it would have a good initial jump then blow out go to the rev limiter at 5200 and plow water for 10 seconds or more before it finally got on plane. Right now with 4 large hole plugs in the holes away from the gear case and the ones closest to the gear case all open. It goes to 3500 you mash it hangs there for a few seconds then blows out to the limiter for 5 or 6 seconds until the boat gets flat and away you go. It's a 31 pitch prop so I know it's going to pull hard but I need to get rid of the blow out.
I have a skid planner that's cut so it's flush with the back of the boat I am going to put on. My idea is that the stock planner sticks out past the rear of the boat 2 inches and I think it opening a hole about the time the boat breaks over and makes the prop cavitate.
I do have one of cbailey's hole shot plates on my Stroker which lets it get on plane with any prop I have with the 1.62's or 1.75's. Prop range is 28p to 34p. With out the plate I would just do donuts with the 1.62's and a 32 or bigger prop. You might consider sending your prop to have it worked for the hole shot.
Yep I have talked to Thom at Hydromotive about reworking the prop. Right now I need to figure out how to tame down the blow out it does as the boat breaks over on to plane. Anybody have any success with installing PVS plugs to back that off?
My 30 is my next one to get tweaked for better holeshot. I do not get blowout at all. I must trim all the way down to get on plane which it does well. But I have enough PVS plugs in it that it will just bog if I don't trim down and it noses over well if I trim all the way down. Doesn't seem to matter the weigh in the boat with current configuration, it acts the same with just me or with 5 aboard. I think this may be due to the foreard seating of the 2+2 though, typically, when adding a passenger I gain better holeshot, and lose acceleration. I want to have it tweaked so that it will tolerate a little more initial venting without blowing out.
I have not run it since I moved a battery forward, but I can only believe that will improve it further.
Was able to find a happy medium. - By adding one more plug at a time until it quit the half way out surging. they also make plugs that still have a smaller hole.
Any more discussion on this subject? I'm trying to get my XOB to stop the extra rpm's just as its about to take off.
2013 Allison XB-21 BasSport Pro
2023 Mercury Racing 300R
Bravo FS 30P
ProMax 30P
Craig, my 30 XOB has been to Roys, it is making a quick stop at river rockets and triton1before coming back to St. Louis. Some drastic measures were taken. All of which I hope don't effect topened.
Cupping profile was changed, some even ground off, and some pitch had to be removed in order to roll the blade as he described for best holeshot. It addition to biting better out of the hole I was looking for the nose to pop sooner.
Not sure I understand all I know about this PVS system. Both of the props I have were the same bad blow out as the boat breaks over. If you plugged them off enough to stop this you killed the low end jump to 3500 rpm. One prop a Croxton 4XL 28 pitch the other a Hydromotive XOB 31 pitch. Thom/Todd have been helping me out on their prop and I sent it back to them the other day. Croxtons prop I got back a week ago. Not sure what he did to it but it's a lot better. But part of what he did was make the holes closest to the case 7/8 of an inch I thought for sure this would make my blow out problem worse but no now this prop will run with no plugs in it and have a pretty good hole shot. Has me scratching my head!
Yeah, like what river rocket posted about adding bigger and more holes to a promax prop I'd have put money on the table it would have blown out worse but he said it cured the problem. I don't get it either.
So my question is; if I have 8 PVS holes on a 28P XOB and right now have one solid plug in only one hole on the second set (those furthest from the gearcase) and initial throttle the prop takes off and as the bow drops it overrevs enough to keep it from being a good hole shot. It's about 5 seconds as is and I know that if the extra revving were not there it would be about 2 to3 seconds.
What say ye?
2013 Allison XB-21 BasSport Pro
2023 Mercury Racing 300R
Bravo FS 30P
ProMax 30P
Oh, and where can I get some plugs that have different size holes?
2013 Allison XB-21 BasSport Pro
2023 Mercury Racing 300R
Bravo FS 30P
ProMax 30P
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