So I'm not crazy... too much stern lift for my liking!
So I'm not crazy... too much stern lift for my liking!
Allison XB21 Prosport Mercury Racing 250XS with a 1.75 Sporty
You can watch the pitch value from both runs. Running really flat in the first video with my standard trim value. Much higher in the second part of the video after giving it more trim. My stock promax accelerates and has more top end at the first trim setting. Agree, the flare ring makes a difference.
Allison XB21 2+2
Mercury 300R
That is so awesome !!
Is the pitch and roll part of your GPS ?
Geoff can drive the snot out of an XB21 as can a few others I've talked to. And I greatly appreciate the fact that he was wiling to put it to the test and evaluation.
So now the question is do I have some of the flare removed or all of it removed??
What are some experiences of XB21 owners who have a favorable opinion of the Promax and use it as their everyday and/or full load prop? How is hole shot with your particular prop with or without a flare ring?
Another question I have for discussion is how do some of the XB21 owners get their particular rig up to WOT top speed? Do some take a "set it and forget it" approach meaning JP is at a set height and max trim is achieved in a very short time and left there or is it a progressive process?
2013 Allison XB-21 BasSport Pro
2023 Mercury Racing 300R
Bravo FS 30P
ProMax 30P
The flare ring on this Promax prop is quite large compared to the original one that you and Robbie welded on the early models. The welded flare ring back then did indeed improve the hole shot substantially over stock on my particular rig.
I have a single 32LB lithium battery up front for my TM. In fact, I recently replaced my 80 LB AGM cranking battery from behind the passenger with a 25 LB lithium and replaced my 63 LB MK Ultrex (24V) with a MK Ultrex (36V) beast which I did not weigh. It is way heavier than the 24V. So if I remember correctly listening to Mr. Allison a few years ago at a rally if weight is removed from one side of a boat and placed on the opposite side it actually has an affect of doubling the weight. I also added another inch of setback for a total of 10.5".
I asked Geoff to test this prop because of his experience with the Promax. I didn't know he never ran one without a flare til we got to talking about it. My boat as described above does not run nearly as well as it did before I made those changes with either my 28P XOB nor this Promax. I could not understand why my XOB didn't perform because I didn't make any changes to that prop. I thought to myself there is no way the changes in TM and battery could have done this. However, it does run similar to the Promax. The Promax pushes the bow down and takes forever for the boat to free up. The XOB is doing the same thing but not quite as bad. And it takes trimming into the upper 8's on the Merc Monitor at max speed to feel the hull lift. Neutral trim with the 1" wedges is 7.5. And as I ran more and more draining the fuel tank below 1/2 made it worse!!
Geoffs boat, looking at his pics-and he can tell us more about what he has on it, looks to be heavier in the rear than mine. I think I lightened up the rear of my boat way too much. I figured the basics of a fulcrum by moving my motor back another inch would help bow lift but removing the extra weight of the AGM defeated that. And adding more weight to the bow with a heavier TM added to that. Now run a prop with a flare ring to produce lift and I've killed performance. The XOB ran 6-7 MPH slower at Hartwell a few weeks ago than a quick run I made at home last year on my local lake with 9.5" setback (no wedges), AGM cranking battery, 24V ultrex, full fuel and normal load running the same engine height and way less trim. I had a lot more running room and time to try to get the same speed as last year but couldn't do it. The Promax was about 10 MPH slower. I ran 92.7 last year with ease in a very short distance with little effort.
Bottom line is these boats are extremely weight placement sensitive (which we already knew) and set up dependent (which Tim Powell has proven) and do not like extreme stern lifting props (duh)
2013 Allison XB-21 BasSport Pro
2023 Mercury Racing 300R
Bravo FS 30P
ProMax 30P
Good stuff right there !
Yep, Well said about the weight sensitivity. Thats why I have put my XB-2003 on a serious diet. The 3.0 liter plus all the batteries and troller was killingthe topend performance. I went to 30#'s of lithiums, replaced a 52" fortrex with a 45"Terrova. Took out the 30# dual pro charger. I have effectively removed 150#'s from mine. Add the 25#'s Ive personally lost since August to the total lost and 175#'s out of the total boat weight has been removed. Next I am gonna replace the 70# Cranking AGM with a 30# Lithium and that will put my weight loss at over 200#'s. That will put me within 75#'s of what it weighed when I ran a 200 2.5 liter, two 27 series batteries and a small hand controlled trolling motor and would run 87 loaded with just me in it.
So bottom line, in my case at least, is that a Bassport Pro loaded by a fisherman for fishing needs a certain amount of weight in the back end of the boat. I forgot to mention that when I was having this trouble getting speed and the nose up I started adding as much stuff as I could in the boat to the back port compartment where the cranking battery was. Speed did increase a bit
2013 Allison XB-21 BasSport Pro
2023 Mercury Racing 300R
Bravo FS 30P
ProMax 30P