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Thread: What lower drive is this??

  1. #46
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    having a prop or two on hand is all part of Donzi Classic ownership, the hulls are very prop sensitive. I forgot about your altitude you numbers are close to mine but I am around 240-250 ish HP and a much bigger boat. If you like fast and loose the 22 ultra may be a prop to look at Hill also makes a prop for the AQ .

    Woobs has a good idea if there is a shop that will help you for a sale that is the way to go.

    when looking for a prop your idea of handling and slip are the big factors. usually 10% slip is the target number I have run faster props than the solas but could only take advantage of that extra speed for seconds in the right conditions and could not keep tract of all the handling quirks.

    run your numbers thru the prop calc the ultra runs at about 15% slip and can go higher the faster you spin it. I would think going up to a 22 ultra would keep you around the rpms you are now maybe a bit lower I would say no lower than 4800. the bow will come up it will ventilate in harder turns and rough water but when you can find calm flat water you can fly the boat it will be fast and loose. I ran a 22 and 24 ultra on my 16 and it wasn't a bad prop but was a handful when pushing it or when having to make quick adjustments.

    not knowing your motor and the altitude going to a 21 solas may put your rpm down to low 4500 or so
    When the sky is grey,look out to sea.
    When the waves are high and the light is dying,
    well raise a glass and think of me...
    When I'm home again,
    boys, I'll be buying!

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  2. #47
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    I know you are looking for a magic prop to give you 3-5 mph more but those gains are usually with a shorty drive or HP

    take the worst case in going to an ultra 22 -600 rpm for the jump of 3 inches of pitch ( 200 per inch) + 200 for the smaller diameter puts you at -400 rpm to 4600 rpm on your setup with 15% slip guess what you are right back at 50 mph

    take the worst case in going to an solas 21 -400 rpm for the jump up in pitch and a push on diameter, turning a more efficient prop that 4600 rpm at 8% slip gets you to 52

    again just a guideline and not taking in the thin air

    and this is all about WOT not taking into account for mid range cruise and ride.
    When the sky is grey,look out to sea.
    When the waves are high and the light is dying,
    well raise a glass and think of me...
    When I'm home again,
    boys, I'll be buying!

    My Ride

    Come Join Us on The Queen Of American Lakes



    Contact Us

    www.lgdonziclassic.com

  3. #48
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    I had my buddy talk with the shop that rebuilt his engine.
    They said it was beefed up to 350 HP
    I am guessing the 19 may have been too small?

    I wish we had a prop shop close enough where we could test some different ones.

  4. #49
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    Assumptions; an 18 with the same drive/engine will be 2-3 mph faster than a 16.

    I did extensive testing with Solas props, running a 19" and 21" on my 16 Ski-Sporter with a 260 hp 350 Chevy and a Volvo 290 with power trim.

    Several things you said don't match my personal experience at all.

    1. Both the Solas 19" and 21" functioned at around 3% slip.

    2. The Solas prop was the most "hooked up" prop I have ever run.

    3. Ventilation is NOT an issue, with 15-5/8" diameter, and huge blade surface, I would believe it virtually impossible to ventilate on a stern drive.

    4. The Solas is the least sensitive to trim of any round ear prop I have run. Trimming the drive up makes very little difference in the boats actual ride attitude.

    5. The Solas is designed to run the boat very flat, with very minimal bow rise.

    My 260 hp engine turned to 19" Solas to 5,000 rpms, and 53.7 GPS mph. The 21" Solas brought the rpms down to 4,750.

    When I replaced the engine with a 430+ hp 409 monster, it would turn the Solas 23" to 5,300 rpms at 65.3 GPS mph. I have heard that strong engines in 18 Donzis running over 5,000 rpms with the Solas 23" put them over 70 mph. I ran an Ultra 26" with this engine, which ran to 5,800, but 64.7 mph.

    The Ultra 24" prop also ran the 260 hp engine to 5,000 rpms and 57.3, but it was a total handful, with a ton of bow rise to minimize wetted surface. It was faster, but almost nowhere near as efficient at cruise.
    “Oh right, because you walked into strippers discount warehouse and said ‘Help me showcase my intellect.’” - Archer

    Bill
    Grand Rapids, Michigan
    1985 Donzi Criterion SS
    1967 Donzi 16 Ski Sporter, C16-409, Has a new home!
    38' Carver Aft Cabin
    1968 Sea Ray SRV 180 w/1975 70 hp Evinrude
    10" RIB w/15 hp 1984 Evinrude

  5. #50
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    you put a 409 430HP in a 16? Holy crap that must've been quite a ride.

    I don't know what to say about it. That is the way it rode. I loved it, my buddy hated it. Part of this is for testing the prop for my boat as well. I will not be pushing 350 HP and my boat is a Barrelback (which I heard was lighter than the x18s.)

    The outdrive trim bolt is in the 3rd position all the way out. Does that make a difference?
    Holding the steering wheel also is a bit of a challenge. It cranks the boat to the left hard. You really gotta hold on.

    He is afraid he is going to bury the nose as well as the prop really lifts the back end puts the bow down.


    I guess we will keep trying to dial it in.

  6. #51
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    It was a handful only because of the inherent looseness of the Volvo helmet style steering, and because I had a traditional cable system, rather than hydraulic.

    I suggest you try the Solas in the middle pin hole. The Solas is designed to make the boat run flat. They don't like to be trimmed up. That could be the source of the instability. They run very counter-intuitively. I have pretty decent seat time in many fast outboard and stern drive boats, and that experience made running the Solas MORE difficult for me to get the most out of because the "normal" rules don't seem to apply.

    If your friend is used to having to trim a drive out to the max to get the best top speed, he is going to have to erase that thinking with the Solas props. Part of the reason they made the 16 more manageable, is because they were designed to run the boat flat; there was more hull in the water, adding to the stability at perhaps a slight loss in top speed because of the increase in wetted surface.
    “Oh right, because you walked into strippers discount warehouse and said ‘Help me showcase my intellect.’” - Archer

    Bill
    Grand Rapids, Michigan
    1985 Donzi Criterion SS
    1967 Donzi 16 Ski Sporter, C16-409, Has a new home!
    38' Carver Aft Cabin
    1968 Sea Ray SRV 180 w/1975 70 hp Evinrude
    10" RIB w/15 hp 1984 Evinrude

  7. #52
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    One last thought regarding the steering wheel torque. I had an advantage because of the power trim. I found that at almost any speed, except wide open, I could tap the trim button and find a setting that resulted in no wheel torque. The drive trim was ever so slightly different at different speeds. What was perfect at say 40 mph, was not good at 30, or 50 mph.

    Too much trim at WOT is going to create a torque monster at the steering wheel!
    “Oh right, because you walked into strippers discount warehouse and said ‘Help me showcase my intellect.’” - Archer

    Bill
    Grand Rapids, Michigan
    1985 Donzi Criterion SS
    1967 Donzi 16 Ski Sporter, C16-409, Has a new home!
    38' Carver Aft Cabin
    1968 Sea Ray SRV 180 w/1975 70 hp Evinrude
    10" RIB w/15 hp 1984 Evinrude

  8. #53
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    kinda hard to test props on two different boats with different HP and Different bottoms

    i would move closer to the sea 350 hp down here is a high 50s low 60s classic
    When the sky is grey,look out to sea.
    When the waves are high and the light is dying,
    well raise a glass and think of me...
    When I'm home again,
    boys, I'll be buying!

    My Ride

    Come Join Us on The Queen Of American Lakes



    Contact Us

    www.lgdonziclassic.com

  9. #54
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    I think we will try to move the trim pin to the middle and see how that goes. On my XK22 I just moved the trim bolt to the 3rd position and it now has a lot of wheel torque. I am going to move it back.

    I know Matt you are right. Originally when I thought we had very similar HP motors is what I meant. I didn't know his was beefed up so much.

    Tough to move away from the cleanest nicest lake in the world for a few MPH

  10. #55
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    when I did most of my prop testing and purchasing/ collecting I used the donzi community as a resource plus I had a friend who had a 19 cig with a volvo 270 so we went partners on most of the props . he had a LT1 CC sbc putting out around 350 hp and I had a 351w and a 250 volvo at around 310 hp. so we were close the 16 and the cig 19 are basically the same bottom. when it came to the larger props 24-28 pitch my ford with its low end torque could get up on plane but couldn't turn them at higher rpm the LT1 seems to have more ballz at the higher rpm band. after testing all the round ear , clever ,chopper, and ultra props we settled on a 22 ultra for me and a 24 ultra for him then the solas came out in 2005 or so we had a prop fire sale and i went with a solas 21 and he went with a solas 23 which put both of us in the high 50's and would hit 60 in the right conditions

    things to keep in mind like Bill said if there are any issues with slop in the steering the solas is going amplify them I never had a torque steering issue with my solas but my steering was pretty tight

    I did run a 25 chopper that made my right arm twice as big as my left
    When the sky is grey,look out to sea.
    When the waves are high and the light is dying,
    well raise a glass and think of me...
    When I'm home again,
    boys, I'll be buying!

    My Ride

    Come Join Us on The Queen Of American Lakes



    Contact Us

    www.lgdonziclassic.com

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