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  1. #1
    Member fishnfireman's Avatar
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    Question cavitation plate foil ?

    Anyone have experience on the 21' hulls with a holeshot foil ??
    Results ?
    Comments?
    Thoughts ?

  2. Member tritontr21's Avatar
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    #2
    Just added one of the CB Marine custom cavitation plates (foil) on my boat a month ago. I get less bow rise, ability to stay on plane even slower, quicker holeshot especially running big over the hub props and biggest thing no loss of speed on top. Also since I do not nomally run XOB's I have not had any quirky handling issues at all.
    Last edited by tritontr21; 11-09-2017 at 04:39 PM.
    Jay McDaniel
    2003 Allison XB21 BasSport Elite 2+2
    2019 Mercury Racing 300R

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    #3
    I had one and took it off....when running Hydromotive X-O/B's my boat drove like crap and lost a solid 6 mph.

    They work as advertised, everything Jay mentioned above.
    Fastbass Marine LLC
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  4. Member tritontr21's Avatar
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    #4
    For the record I am having to retune both my bravo and my promax pvs holes as adding the foil put a slight bog in them but I opened 1 hole on my promax and the bog was gone more or less the same on my bravo. It basically requires adding a little ventilation on my setup. Your 300 will definitely need 2 or 3 times the venting in my opinion. Geoff may have further calculations to back this up! I do not have any experience with elevation. Or a 300/1.75 combo but I expect it to be somewhere between a 250/175 and a 300/1.62 requirements!
    Jay McDaniel
    2003 Allison XB21 BasSport Elite 2+2
    2019 Mercury Racing 300R

  5. Member tritontr21's Avatar
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    #5
    I tend to launch my rig at higher rpms than some like! 4500-5000 is where I keep mine!
    Jay McDaniel
    2003 Allison XB21 BasSport Elite 2+2
    2019 Mercury Racing 300R

  6. Member River Rocket's Avatar
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    #6
    I added mine on the last run of the season. I ran it with my overhub prop that already launches Really good and it was 34 degrees that day. I didn’t do any 5-85 passes. As Jay and Tim have said my bow rise was much better. I didn’t see any negatives and ran it up just under 95 and didn’t notice an issue. I ran 70 miles that day and had heavy chop at times, cruiser waves, boat traffic, smooth water, and tight turns. It was a river run so I was passing boats and jumping wakes. I felt like I tossed a lot of conditions at it that day. I also had a 250 plus lb passenger ride with at one point and it got both of us out without issue. Right now I’m running flat outside edges. I will be Testing flat vs downturned edges sometime this winter. My promax will be a better test prop. Never got a chance to run up in the high 90’s but I don’t think it will be an issue. I’m going to keep it as it’s designed to be a step for the kids to use to get in the boat.
    Allison XB21 2+2
    Mercury 300R




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    #7
    I had the allison foil on my 250XS/xb21 Pro and kept breaking off the small SS bolts that held it on. And yes you guys are correct it requires changing PVS plugs due to how it changes the water flow around the prop. It did, however, greatly reduce bow rise on hole shot and made it a bit quicker

    Also, I removed some of the aluminum material in front of the side gearcase bolts to reduce its overall length which improved hole shot and reduced the amount of bolts breaking. scj should have some pics on here somewhere on an old post
    2013 Allison XB-21 BasSport Pro
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  8. Member fishnfireman's Avatar
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    #8
    Thanks for the replies.
    Have been hesitant to put one on this boat based on the results I had with my old 2003 when running the 225 Promax... It was great for hole shot and slow planning speeds. But did have some high speed handling quirks at times. The biggest killer for that rig was running big waves--Anytime you nailed the throttle to pick the nose up to keep from stuffing a wave it did what it was designed to do which is push the bow down. After a couple of trips where I submarined some waves-- I took it off. Guess the only way to find out for sure on this bigger hull is to try it.

  9. Member tritontr21's Avatar
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    #9
    If running in extreme big waves I suspect it would require less negative trim with a foil to keep the bow up more. I had no issues in some pretty nasty stuff on my 2.5xs with a foil but try to avoid the nasty stuff if possible. I will say that with engine in full tuck it still wets the carpet but I'm almost never tucked except holeshot and only for a split second!
    Jay McDaniel
    2003 Allison XB21 BasSport Elite 2+2
    2019 Mercury Racing 300R

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    #10
    With the foil I could launch with the trim up on 3.5, that was nice when I had wedges because it helped keep the bow up.

    I have to say, when I ran the foil, I was only running even with the pad, now I've made several changes and can run 1" above but I have not tried the foil again. I am a little gun shy, plus I gave it away
    Fastbass Marine LLC
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    #11
    Barrow it back for a little testing.
    Quote Originally Posted by Tim Powell View Post
    With the foil I could launch with the trim up on 3.5, that was nice when I had wedges because it helped keep the bow up.

    I have to say, when I ran the foil, I was only running even with the pad, now I've made several changes and can run 1" above but I have not tried the foil again. I am a little gun shy, plus I gave it away

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    #12
    What jay and Tim said is accurate

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    #13
    Quote Originally Posted by Strokerdean View Post
    Barrow it back for a little testing.
    It is still local but he had to trim it so it would fit a wingmaster gearcase.
    Fastbass Marine LLC
    We specialize in NEW and USED ALLISON BOATS, Blazer Boats, Platinum Mercury Marine Repower Center, AquaTraction Flooring, and custom marine electronic installations on beautiful Kentucky and Barkley Lakes.

    2022 Allison XB-21 BasSport Pro Elite
    2022 Mercury 450R

    2012 Bullet 21ss
    2005 Mercury 300X

    https://youtu.be/FOnAGNWOgZ0