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Bertram 43' Sportfish Repower

Discussion in 'Bertram Yacht' started by tmcgee57, Aug 13, 2010.

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  1. tmcgee57

    tmcgee57 New Member

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    Hey all,
    This is my first post!
    Need help with info on repower of a 1989 43' Bertram Sportfish, power on board is (2) 6-92TA Detroit Diesels, 550HP when new. What are the problems associated with this type of project? What engines do you recommend? Any help is appreciated.

    Thanks
  2. chesapeake46

    chesapeake46 Senior Member

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    Are the existing engines not worth rebuilding ?
  3. Pascal

    Pascal Senior Member

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    "What are the problems associated with this type of project?"

    COST! while older Bertrams or Hatteras are probalby the most worth of a repower, the costs are very high. If you intend on keeping the boat for a long time it will be worth it but otherwise you'll never recover the cost when it comes time to sell.
  4. tmcgee57

    tmcgee57 New Member

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    I don't know at this point. We were considering fuel efficency and cruise speed as one reason to repower.
  5. tmcgee57

    tmcgee57 New Member

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    That is one of our main considerations, don't know how long we will keep the boat. The hull and the rest of the boat are in very good shape though. Thanks guys
  6. greg807

    greg807 New Member

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    I also have a Bertram 43 with DD 6v92's and have been considering repower. As pointed out earlier, cost benefit analysis is big question. Looks like the Cummins QSC at 600hp is the best alternative. There is a 43 in Puerto Rica currently being repowered with Cat C15. Check out boatdiesel.com for information and pictures on the 43 in Puerto Rica. Dont know how to resize pictures for posting, but I have pictures of Cummins QSM repower of 43 by Unlimited yacht Services in Florida... if you are interested send me a private message.
  7. dockeffer

    dockeffer New Member

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    reopower 43

    I have seen 43 get 8 cylinder mans. The neg on the mans is they are expensive to maintain, tend to smoke at idle. I think the best choice would be the 8.3 liter c series cummins at 540 or 600 hp. The new common rail mans make more hp. but are expensive.
  8. Jack D

    Jack D New Member

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    How did you make out? I just did my 95 43 with 680 hp QSM 11's and are very happy.
  9. Capt J

    Capt J Senior Member

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    What performance numbers are you getting out of her? What gear reduction, and props are you running? Fuel burn?
  10. Breckster

    Breckster New Member

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    That’s a beautiful blue 43 Jack. Do you still have the 6v92’s?
  11. PierFection

    PierFection New Member

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    Just about to finish up a repower of my 1988 Bertram 43 with QSC 500. SeaBoard Marine is doing the install. I will post up more information when we finish and sea trial.

    Here is a little information on what has been done so far.

    We removed the old Detroit Diesel 6V92’s rated at 550hp. Had to strip them completely down to short blocks in order to get them out the salon door. The salon door is 28 inches wide and with the motor strip to short blocks the 692s were 26 1/2 inches wide. Otherwise we would’ve had to cut the whole rear wall to take them out. Removed the Alison MH 1.5 transmissions. Had to replace the 2 1/4 inch shafts. The original shafts would be about 6 inches too long when installing the in-line 6 QSC. The shafts might have been able to been machine, however it would have been very difficult because of the threaded keyway and tapered shaft of the shaft design, Also there was a little bit of a problem with the old couplings fitting to the new ZF transmissions. It was determined to be easier to just replace the shifts that were 30 years old. The bulk head in front of the engine needed to be trimmed to allow front access to the motor, and all of the front pulley‘s. Tony added his double double fuel system with priming pump. The transmission selected was the ZF 286A at 1.75.

    With the boat fully stripped down for a sea trial prior to the engines being removed she would do 2350-2400RPM and 27-28kts. Burning 30-32 Gpm. this was with empty holding tank empty water tanks, 100 gallons total fuel, and most supplies removed. I got to experience firsthand what the chine walk is. The boat was so lite and going so fast, that it would fall to one side of the deep V and ride on that side. No amount of trim tab would roll it back up straight. However if you slow down or turned the other direction it would ride up on the other side of the V. This led me to believe that anything over 600 hp would just be either a waste of money or let you just cruise your motors at a much lower RPM. These boats do not need more than 500 to 550 hp max to run. It looks like about 24 to 26 kt is the fastest my boat should cruise. At least when it’s that light in weight. Which is another factor. With the QSC re-power, my boat will be about 3000 pounds lighter in the engine room. To compensate for this I removed the four 8D batteries from under the lazaret. We moved two of the 8D batteries into the engine room as a house bank, and put for group 27 batteries for engines only divided into two groups of two batteries. I’m going to have built-in fish holds below cockpit where the batteries used to sit. This boat never had any fish holds.

    Anyways I will post more information when we complete the project. If anybody is looking to do a QSC re-power I will have a lot of information for you.
  12. Capt Ralph

    Capt Ralph Senior Member

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    Please keep us ole Bertram fans up.
    ,rc
  13. PacBlue

    PacBlue Senior Member

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    Nice of you to post, looking forward to the sea trial results with new power.

    Regarding the chine walking - with no water and 100 gallons of fuel, the shift of the center of gravity was too far forward. The Bertram hull wants to have the center of gravity aft to prevent chine walking, which in your case was probably attributed to the forward planing sections being too 'engaged".

    This is your challenge in the repower - keeping your center of gravity aft even though the engines are lighter, etc. There are several Naval Architect topics on the subject matter.

    Note that your 43 Bertram Hull running surface is identical to the 43 Cabo with the exception that Cabo did not use the running strakes. They have higher hp and do not chine walk.
    Last edited: Mar 22, 2018
  14. Capt J

    Capt J Senior Member

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    I agree with this. I also would leave the batteries in the factory location right now. You lightened the motors but also sounds like they moved forward. Take good pictures of the water line and measurements at several points fore and aft, then do it again with the new motors. Sportfish that cruise 25 knots and faster, like the weight aft, you can always get the bow down with the trim tabs and pickup more stern lift at the same time. You can always move the batteries later, if the trim is too far aft, I wouldn't do it now as the motors are close to balance point.
  15. PacBlue

    PacBlue Senior Member

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    I believe the OP experience chine walking in a light load condition with the original 6V-92's on one last trip.

    I would be concerned with moving any Batteries from their Aft location to a forward location. Would at least compensate with robust fish holds that weigh as much as the 4 x 8D batteries that are scheduled to be removed from the Lazarette.

    The balance game is tricky when you do not have a Naval Architect and a lines plan that is entered into a stability software program like Rhino or others. The weight shifts we are talking about are all in relationship to the physical center of gravity and the vessel's center of buoyancy. The Chine Walking takes into consideration the Planing Area and those locations.

    Donald Blount has a good article on the topic, google "Dynamic Stability of Planing Boats" for a NA's perspective of the issue.

    Here is a the classic diagram for starters, it is assuming that the LCG and LCB are in the same location, i.e., the boat is level as it sits in the water with all gear and full fuel/water onboard:

    upload_2018-3-23_8-31-37.png
  16. Timm

    Timm New Member

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    When I worked in engineering for Bertram in the late 80's, we had this issue with the then new 50. We traced it to the trim tabs mounted under the boat. They seemed to be unloading the chines back aft and because they were further inboard, the hull essentially had less beam back aft when on plane to support all that weight aloft. We moved the tabs aft so they were halfway past the transom and it seemed to fix the problem. The 43 was introduced while I was there and in our testing ran beautifully and didn't exhibit the same issue as far as I know. We normally ran with more weight on board though. I agree with leaving the batteries back aft, although I disagree with calling it chine walking. Chine walking is usually when the boat skips from side to side at high speed, like on a small runabout with too much power. Falling over to one side isn't the same. These hulls as well as the 37, 50 and 72 all had straight sections in the bottom from the inner chine to the keel. They seem to be quite happy to run on that long flat surface when they "fall" over. I don't know if the bottom shape has anything to do with it, but I am curious.
  17. PacBlue

    PacBlue Senior Member

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    Good point on the chine walking description, what the OP experienced when the boat (unexpectedly) leaned to Port and stayed there or to Stbd and stayed there as well is classic Dynamic Instability. Chine walking would be a continuous Port / Stbd oscillation with a lack of correction by rudder input, resulting in a feeling at the helm of a lack of control. Usually corrected by pulling back the throttles.

    It would be interesting to hear how the OP's repower is going?
  18. Capt J

    Capt J Senior Member

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    Or giving it even more throttle. The Donzi classics would chine walk from 45-60mph, but get them over 60 and they’d straighten out.
  19. chesapeake46

    chesapeake46 Senior Member

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    This can also lead to the feeling you need to change your shorts.

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