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Propeller Replacement question

Discussion in 'Technical Discussion' started by seajewel, Dec 30, 2008.

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  1. seajewel

    seajewel New Member

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    Dec 27, 2008
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    Location:
    De Anza Marina, Newport Beach, CA
    I am in the process of trying to have extra props and in need of replacement. I received great advice from senior members about a mishap I experienced as a new boater. I have been reading Chapmans like a bible!! Advice I get from the book about different props is basically left to personal preference.
    I have a Carver 33SS (38 LOA) with twin 6.0 mpi crusaders that comes with standard 22X 22 nibrals. I found 2 different deals for brand new 21X22 and 21 X 24 nibrals ( obvious difference is diameter and pitch). It would make sense to go for the 21X24 to reduce rpm load on my engines ( with regular gas andf less heating that way?) and maybe enhance gas mileage?? Also -- having a higher pitch when I put the boat in gear without using the throttles, what does that do to my idle speed ( go higher I would guess) ( but a smaller diameter might make it negligible)..
    I am just trying to process all this wonderful new boating language!
    Thanks for all your help.
    Hisham :)
  2. Capt Bill11

    Capt Bill11 Senior Member

    Joined:
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    Location:
    Sarasota/Ft. Lauderdale FL
    For the time being, and if your boat is running up to spec with your original props, I would stick with spare props that are the same as your originals.

    Props can be tweeked later after you get more time under your belt running the boat. You might try talking with some folks on a Carver owners forum and see what changes they have made to their props. As well as talking with a prop shop.

    And quite frankly, unless you find a killer deal on a used set of props, I wouldn't be in a big hurry to get a spare set.

    To learn more about props, take a look at:

    Propeller Handbook : The Complete Reference for Choosing, Installing,
    and Understanding Boat Propellers

    by David Gerr

    International Marine Publications Systems
  3. seajewel

    seajewel New Member

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    Location:
    De Anza Marina, Newport Beach, CA
    Thank you Capt Bill -- good advice!
    I received another message from Nicholas on another thread --basically - I just need to speak to a prop shop and get familiar with my boat's personality as I am sure even two of the exact same boats may have different traits on the water! I will for sure try to get that book by this week-end!
  4. CODOG

    CODOG Senior Member

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    Location:
    Bournemouth, southern England
    Sorry to state the obvious but double-check the number of blades, shaft diameter and taper / keyway spec before you buy replacement props. Decent suppliers will ask these questions at point of order, others will just send you what you order. There is a difference, as a few have found out.
  5. TedZ

    TedZ New Member

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    Clayton, NY 1000 Islands
    Gerr is excellent but his info is dated. Four was rare and 5 bladed technology was not available in small (our size) props when his book was written. If money is no object talk to the prop manufacturers. you should be able to improve both mid-range and top speed with increased efficiency (MPG) at all speeds (i know not possible but, in fact, it is being done all of the time) with modern props. Drawback is they are expensive so the payback is protracted.

    My $02.

    Ted
  6. Capt Bill11

    Capt Bill11 Senior Member

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    Good point Ted. But it is the best book I've seen on props.

    And if you do go with new props, look very closely at Veem's.
  7. hookumup

    hookumup New Member

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    Feb 1, 2009
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    Location:
    jacksonville fl
    props

    my experience is to check with the boat manufacturer and compare to what you have. An objective of propping is to control engine load so that the max mfg engine rpms are obtained. regardless of what is accomplished by tweeking propellers it all comes back to the engine.

    tweeking has only to with increaseing the propeller efficiency while it is doing it's job. that said you can spend a ton of money chaseing margines particularly if your boat is near its hull speed. Truly, you can tweek to your crusing rpm which for a gas engine is 65 yo 70% of max rpm, very generally speaking. At least on diesels the fuel burn curve is predictable by the engine maker

    i would grease the shafts where the prop slips on and make sure the shaft zincs are near a strut. on our stuff, we have the propeller hub taped so that a piece of metal can be placed over the end of the shaft with bolts passing thru which screw into the propeller hub as avery neat way to pull the propller off

    I would suggest you read up on the relationship among diameter, pitch and cup
  8. anthony m

    anthony m New Member

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    Location:
    West Palm Beach, Florida
    does anyone out there own a carver 33ss, 35ss or 36ss with 8.1 engines? I just repowered my carver 35ss ( same boat as 33ss and 36ss) and I upgraded the engines from the crusader 6.0 crusader to mercuiser 8.1s. the original props were 22x22. they did not work. I am in playing the guess a prop game and already purchased uses 22x28 and 22x26. neither are getting me up to rpm past 4200. I really need to know what the boat came with when 8.1s were factory installed. please help..
  9. Capt Ralph

    Capt Ralph Senior Member

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    What did the 22 x 22s spin @ WOT?
  10. anthony m

    anthony m New Member

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    Thank you for responding, the 22 x 22 spun out like an egg beater. Rabbit up to 5000 RPM And could not get on plane. Up to 12 mph.
    Then I bought a pair of 22 x 28 and was able to get up to 22 mph but would only turn 3200 rpm wot.
    Now I bought a pair of 22 x 26 and boat gets up to 30mph but wot is 4000 rpm.
    I am not sure if I should invest in 23 x 24 or 22 x 25. This prop thing is a pain in the ass and very costly. Thank you for your help
  11. Capt Ralph

    Capt Ralph Senior Member

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    Prop shops can usually offer suggestions. Carver still answers the phone.
    Beat 2 inches out of those 26s.
  12. Pascal

    Pascal Senior Member

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    Talk to a good prop shop, give them the specs on your boat, engines, etc they can calculate what you need and adjust the pitch on your props if they re close.

    This will save you a lot of time and money
  13. anthony m

    anthony m New Member

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    Yes thank you for the response. I really wanted to find someone with the same carver that had 8.1s factory installed.
    Btw- there is a huge difference in torque going from the original 6.0 crusaders (320hp) to my new 8.1s. (380 hp)
    Although gas consumtion is worse, I no longer have to worry about too many people or too much weight.
    My carver was a slug with the original 6.0s and 6 people on board with 1/2 tank of gas. I abused and burnt out those 6.0s. Good engines for a midsize cruiser but they do not belong on a 35ss carver.
  14. dsharp

    dsharp Senior Member

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    lake jackson, tx
    Check the installation notes and see what mercruiser wants the wot to be with a full load. Did you use the same gears? They used to wheel them at 4400. As previously stated , take 2” of pitch out of the 26” wheels and you will pick up the 400 rpm. If you don’t let the engines reach the rated rpm you will likely have issues with detonation and cause internal damage. Are you running a 3 blade or 4?
  15. anthony m

    anthony m New Member

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    Yes I am taking them off this week and having them dying down to 22 x 24 . Does anybody need a pair of 22 x 20 to 1 1/2 inch bore or 22 x 28 one and three-quarter inch bore . Please make me any offer so I can get them out of my garage.
  16. Fishtigua

    Fishtigua Senior Member

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    Mick's props are pretty identifiable. Micks props.jpg Micks props.jpg

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