Prop testing on a 27 Eliminator Fun Deck
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Prop testing on a 27 Eliminator Fun Deck

  1. #1
    In the hunt! rsscoggins's Avatar
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    Default Prop testing on a 27 Eliminator Fun Deck

    I have a "new to me" Eliminator Fun Deck with a 525 with a Bravo XR drive with 1.5 gear ratio. Previous owner stated that he had it set up with a higher than usual x-dim which I believe because if you trim it too high, the drive shower will contact the underside of the swim platform.

    The boat came with a 26p Bravo 1 4 blade prop. With the stock 26p prop, I thought that planing was a chore with a lot of bow rise. Pulling my kids on the tube at slow speeds was challenging as well.

    Tonight I tested with a 24p Maximus 5 blade. All testing with both props was done in 100 plus temperature with 3/4 tank of gas on the left and 1/4 on the right. Speeds are from an Autometer GPS speedo.
    26p Bravo I 4 Blade (all stock 15 1/4 diameter)
    NOTE: Getting on plane with more than 3000 rpm and the prop will blow out - 2500 would allow it to plane at about 1/2 throttle. This prop needed much less trim than the Maximus. At 2800 - 3000 rpm seems like the prop is slipping or cavitating as the boat feels loose and RPMs will fluctuate.

    Time to plane: ??? (will get on Sunday)

    RPM Actual Speed Slip Comments
    2500 22 46% WaterSports
    3000 36 27%
    3250 40 25%
    3600 51 14%
    4250 62 11%
    5000 74 10% Gets to 5000 quick


    24p Maximus 5 blade (all stock 15 5/8 diameter and full diffuser ring)
    NOTE: needed more trim with this prop to break the hull loose and obtain speeds. On plane 2200 rpm is all she's got - wide open.

    Time to plane: 9 to 10 seconds
    RPM Actual Speed Slip Comments
    2200 22 34% Watersports
    2500 30 21%
    3000 41 10%
    3500 49 8%
    3750 53 7%
    4000 57 6%
    4500 63 8%
    4800 68 7% 4800 max RPM - Slow to get there

    Calculated slip numbers are lower with the Maximus - some look almost too low.

    With the 26p Bravo, getting on plane is a chore. 2500 to 3000 1/2 throttle, bow rises high, s-turn and she rolls over. With the Maximus, bow doesn't rise as much but full throttle and 2200 rpm is all its got. I need to get the time to plane with the 26p Bravo.

    With the Bravo, I needed minimal trim 3 to 4 on the indicator to obtain speeds. The Maximus required much more 6 to 7 or more to obtain the speeds. Bravo pulled quicker to 5000 RPM than the Maximus did to 4800 rpms.

    The Maximus seems more stable at all speeds and eliminates the rpm fluctuation between 2800 and 3000 that I get with the bravo which is due I am sure to the Bravo just not hooking up and slipping at this speed.

    Not sure how the larger diameter of the Maximus factors in - it is definitely a bigger prop as I was initially worried about it hitting my water pick up for the drive shower. The Maximus has the solid PVS plugs - I am tempted to yank them to see how it responds with none. I just noticed on Mercury's website Maximus® | Propellers | Mercury Racing that it says that the 15" diameter is for "the awesome performance Cats and go fast party boats" so I guess the diameter could be part of my problem. The website also says "The shortened exhaust tube (some people refer to it as the diffuser ring or barrel) settles the stern of select hulls, resulting in a 2-4 mph increase in top-end speed. " This is consistent with what I have been told about removing 5/8" off of the diffuser ring.

    I am going to run the Maximus tomorrow and then put the 26p Bravo back on Sunday to get back to back testing. More to come.
    Last edited by rsscoggins; 08-12-2011 at 10:03 PM.
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    Numbers look good. Based on the numbers I don't think your "x" is to high, it is not uncommon for the drive with a drive shower installed to hit the swim step, install some trim ram spacers to limit the trim rams and you will not have to worry about crunching the drive into the step. This is easy and very inexpensive.

    The maximus is a big heavy prop, 9-10 secs to get on plane is along time, take out your PVS plugs and try it again. This will allow some slipping and get you more RPM'S and into a better power range.

    As for the cutting the defuser ring, I have found the best results on boats with some sort of setback, ITS, NXT or a BOX. It will allow the boat to settle and carry the nose better. On a Magic deck boat with a Merc 700 NXT package 1.50 gear 30p Maximus boat runs 88-89, but very "squirrly" on top end. Trimmed off the defuser and gained 3-4 mph and the boat was on rails !!

    If you do not have trim tabs I would NOT suggest cutting the ring, that little lip does alot to help the boat get on plane, the boat may not even get on plane with a standard gimble package. If your " one of those" that just has to try it, cut the ring off clean with a cutting wheel it can be welded back on if you don't care for the results.

    All of this is based off real actual experience and seat time !! I hope this helps.
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    In the hunt! rsscoggins's Avatar
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    Removing the PVS plugs (all 5) had no impact - still 2400 wide open is all she's got until it rolls over. I think the larger diamet and additional grip of the 5 blades is killing the ability of the engine to spool up.
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    Try removing or you can cut the exhaust bellows, this will allow air to be drawn through the hub and across the prop. This should be done anytime your not useing thru hub exhaust.
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    So I put the 26p Bravo 1 back on today. WOW - it is way better getting on plane than the Maximus - 5.5 seconds although the bow rise is a bit much, it doesn't last long. Planing was the main reason for looking for something other than the 26p Bravo 4 blade and possibly the ability to run at a slower speed down low.

    The 4 blade seems to be more sensitive to weight placement than the 5 blade. If I have people shift side to side with the 4 blade, it will list to the side with the most weight. With the 5 blade, it didn't really matter where folks sit.

    You will notice in the charts below that from 2500 to 4000 rpm the Maximus carried a higher speed at the same RPM than the Bravo which is interesting but above 4000 the Bravo was faster. Based on the testing this weekend, I don't know if it is worth jacking around with a 5 blade to get it to perform. I will talk with some prop guys but I am thinking that the 4 blade might be the best setup.

    26P Bravo 4 Blade
    Time to plane:
    5.5 seconds
    Drive Ratio RPM Pitch Actual Speed Slip Theo Speed
    1.5 5000 26 74 10% 82
    1.5 4750 26 70 10% 78
    1.5 4500 26 66 11% 74
    1.5 4250 26 60 14% 70
    1.5 4000 26 56 15% 66
    1.5 3750 26 53 14% 62
    1.5 3500 26 43 25% 57
    1.5 3250 26 40 25% 53
    1.5 3000 26 36 27% 49
    1.5 2750 26 30 34% 45
    1.5 2500 26 22 46% 41



    24p Maximus 5 Blade
    Time to Plane: 9-10 seconds
    Drive Ratio RPM Pitch Actual Speed Slip Theo Speed
    1.5 4800 24 68 7% 73
    1.5 4500 24 63 8% 68
    1.5 4250 24 59 8% 64
    1.5 4000 24 57 6% 61
    1.5 3750 24 53 7% 57
    1.5 3500 24 49 8% 53
    1.5 3250 24 45 9% 49
    1.5 3000 24 41 10% 45
    1.5 2750 24 35 16% 42
    1.5 2500 24 30 21% 38
    1.5 2200 24 22 34% 33
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    Junior Member FlyinBrian's Avatar
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    Maybe I can get some hlep here - Sounds like the Eliminator may be fairly close weight to my boat, I have a 28ft LaveyCraft Party Prowler w/ 525 merc, Bravo III XR with 25 props. With full tanks, 2 riders I am lucky to see 62 mph @ 5400 rpm? Been contemplating on going to Bravo I XR with 25 or 26 prop. However dont want to lose the hole shot as I can pull skier / wakeboard with no problem. Have trim tabs to help plane faster and control... but I want it all !! Quick out of the hole, handling and get more mph. Any suggestions ?
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    Senior Member EdonShano's Avatar
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    Quote Originally Posted by blp View Post
    Maybe I can get some hlep here - Sounds like the Eliminator may be fairly close weight to my boat, I have a 28ft LaveyCraft Party Prowler w/ 525 merc, Bravo III XR with 25 props. With full tanks, 2 riders I am lucky to see 62 mph @ 5400 rpm? Been contemplating on going to Bravo I XR with 25 or 26 prop. However dont want to lose the hole shot as I can pull skier / wakeboard with no problem. Have trim tabs to help plane faster and control... but I want it all !! Quick out of the hole, handling and get more mph. Any suggestions ?
    ADD the Whipple or put in a bigger motor (more HP) put in a upgraded XR then you can go with a bigger prop...good luck...
    Formally know as UNFORGIVEN...
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