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3 blade vs 4 blade props on 54' Bertram

Discussion in 'Bertram Yacht' started by bluesuit, Aug 3, 2015.

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  1. bluesuit

    bluesuit Member

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    I own a 1990 54' Bertram with 12V92 TA engines (non ddec). I have a pair of S & S 4 blade wheel 30 inch diameter with 30 degree pitch. I cruise at 25 knots @ 1950 rpms burning 80 gph. 2250 @ wot. I understand the boat shipped from Bertram with 3 blade 30 x 31 wheels of which I still have in storage.
    Question: If I go back to the 3 blade wheels, could I get more speed or should I leave well enough alone?
  2. PacBlue

    PacBlue Senior Member

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    Short answer - 3 blades MAY get you a little more top speed but subject to the following:
    If 2250 is WOT, you are about 50 - 100 rpm short, may be carrying a little extra pitch, if bottom is clean, engine is in tune and everything is in working condition. 4 - blades are a bit smoother and will probably give your best cruise. So you are slightly over-pitched by about 1/2", but you can continue to run, keep it below 2200 rpms so as not to overload the engines. I would leave it well alone for now, use them as emergency spares. Factory propeller selection can sometimes lean towards better top speed for best advertising position, but conducted at lighter loads, not true outfitted weights. I bet she is pretty responsive while docking and maneuvering with the 4-blades as well.
  3. Capt J

    Capt J Senior Member

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    I went through this on a Hatteras......but the 3 blades will give you better top end and probably better cruise speed, about a knot. You may experience a little more vibration with 3 blades, but they handle around a dock better, boat will turn more when bumped in gear or fishing. 4 blades will carry a heavier load better, get on plane better, and be smoother, and possibly maintain a more even speed in a rough sea state...........You can always try them.

    I agree you're a touch overpropped and would rather see a little RPM's over 2300 than under.
  4. DOCKMASTER

    DOCKMASTER Senior Member

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    Agree with the comments above. You are a bit overpitched. You want to see 2300 when the boat is loaded with fuel, water, etc. My 54 Donzi with 12v92's (DDEC) will get to 2300 even when fully loaded.
    Also curious if you always cruise at 1950 ? If I'm fully loaded with fuel, water and gear and turn on my engine load % 1950 would have me bumping above 80%. Of coursse I'm pretty conservative so usually run 1850- 1900 and keep it in the mid to low 70% range. I'm also not sure how the weight of your Bertram compares to the Donzi or the conditions you run in. I have a lot of current and wind often. Lots of contributing factors to consider.
  5. bluesuit

    bluesuit Member

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    I
    I almost bought a 54 donzi! Roscioli builds some fine boats! Send me some pics maybe it was the one I passed on. I think the Bertram is a little heavier than a Roscioli. What do you cruise at?
  6. DOCKMASTER

    DOCKMASTER Senior Member

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    I bought mine in Newport Beach, CA in early 2012. Was named Tiger Shark II but I changed name to Vigorous. If I run at 80% and not into a 2+ knot current I run about 26-27 knots. My typical cruise is 23-24 knots at 73-75% load. WOT is 31-32 knots. With heavy fuel and water I'm about 80k pounds.
  7. bluesuit

    bluesuit Member

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    I cruise 23-25 knots @ 1950. i think I'm over wheeled though. best thing to do is haul out and let an old time prop man tweak them. I'm in new orleans. my boat has been in the gulf coast area since new.
  8. DOCKMASTER

    DOCKMASTER Senior Member

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    Sounds like a good idea. Before you haul out make sure you take and record some good data on RPM's, conditions, boat loaded/unloaded, etc so your prop guy knows what you need. You may want to have them scanned as well to make they are true to what you think they are.
    Personally, I would stay with the 4-blade. Having had boats with 3 and 4 the 4-blades run smoother for sure. I'm happy to give up a little speed for less vibration but I'm not certain I'm even sacrificing any speed.