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35 Bertram w/Cummins 6BTA 370Hp

Discussion in 'Bertram Yacht' started by boattc, Oct 14, 2011.

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  1. boattc

    boattc New Member

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    Is anybody on the forum running these engines in their 35? If so, what props are you running? Finishing a repower and looking for some prop clues.

    THANKS

    -Daryl
  2. RER

    RER Senior Member

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    21 Dia x 24 Pitch - 4 blade
  3. dsharp

    dsharp Senior Member

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    Gear ratio would need to be known before you compare
  4. Capt J

    Capt J Senior Member

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    Contact a good propellor shop such as Frank and Jimmy's in fort lauderdale, they should be able to get you really really close. Have the specs of the origional engines, gear ratio and size, as well as the new gear ratio.
  5. boattc

    boattc New Member

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    gear ratio

    sorry bout that ratio is 1.5-1

    Thanks Daryl:confused:
  6. dsharp

    dsharp Senior Member

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    I ran the numbers through a prop calculator and the rec. was 22 X 23. An inch of diameter is roughly the same as 2" of pitch, so the 21 X 24 is close to the same blade area. It's not unusual to have to drop an inch of pitch of a recommended prop since boats tend to weigh more than advertised. With the deep v Bertrams aren't the easiest boats get through the water. Try to keep the boat as light as you can.
    Last edited: Oct 16, 2011
  7. dsharp

    dsharp Senior Member

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    Did the boat have 3208 Cats originally? I think those used to run a 19" prop. What do you have to start with?
  8. boattc

    boattc New Member

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    props

    the boat had 555 cummins 2;1 gears 23-23 wheels.

    Thanks Daryl
  9. Capt J

    Capt J Senior Member

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    Why would you want to increase diameter at all? Diameter doesn't give you any speed, you just need enough of it to get the boat on plane and such, wouldn't it be quicker to just keep adding pitch if the factory diameter was sufficient for the hull, and the boat weighs the same or less. The cummins should weigh less than the old 3208's.
  10. dsharp

    dsharp Senior Member

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    I don't think he wants to increase diameter. He's going from a 555 with 2:1 to a 370 hp with 1.5:1 . I would be tempted to run what you have and see where you are. It sounds like you're going to have to cut the wheels down a little. I would agree that you would be better off to cut the wheels down an inch rather than take out a couple of inches of pitch.
  11. Capt J

    Capt J Senior Member

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    Well according to your calculations and prop size you recommended, his origional props look to be fairly close and are worth trying to get a baseline and see where it's at.

    Was this 35' Bertram with 555's out of Pompano Beach, FL a few years ago and named "Scorpio" or something like that? With a davit and dinghy on the bow? I was involved with that boat and it ended up going to Texas when it was sold.
  12. boattc

    boattc New Member

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    confused

    We run what we started with I ran the prop calculations & came up with the same results that the 23-23 was close port motor has hig ex temp the rebuilder said to much prop so we cut them down to 23-21 same results talked with a cummins tec he said cut diamater so we had them cut them down to 21-21 still had high ex temp port rpms a little low put on a set of 20-22 off another 35 that we are repowering with 370 cummins also still high ex & rpms are low by 25 stbd & 40 port. This is why Im trying to reach out & find somebody that is running these motors in a 35 bert. I think we have a problem with the motors but I need to exhust all posibiltys of props. Here's one thing that is got me confused the other 35bert that we are repowering had 3208's at 260hp 1.5 gears 20-22 3blade props. Another customer 35bert is running 3116 cats 300hp 1.5 gears & 20-22 3 blade props. :confused:

    Thanks Daryl
  13. boattc

    boattc New Member

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    Capt J I'll ch and see what the name of the boat was It did com from Fl about 10 years ago.
  14. dsharp

    dsharp Senior Member

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    If you have had to take out 2" of pitch And cut the Diameter 2" how much has the rpm's changed? What's the story on the engines? something doesn't add up. Are you running the rec. exhaust piping and mufflers?