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Viking 53' Convertible

Discussion in 'Viking Yacht' started by Lunderic, Jan 11, 2021.

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  1. Lunderic, Jan 11, 2021
    #1
    Lunderic

    Lunderic Member

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    I recently purchased a 53' Viking with MAN 2840LXE 820 HP. I'm going through all systems repairing and updating as needed. I was wondering what cruise others are getting with the same engines. At sea trial with full fuel/water, 6 guys, dirty bottom, barnacles, and about 20 years of chipping bottom paint boat made about 26 knots @2340 RPM. At 1950 she was making 22 knots. Engine surveyor recommended running at 1950 (they felt it was best). They also told me it was at 80% load at 2150 but I'm not exactly sure what they were measuring. I cruised for about 7 hours at 1950 and it burned approximately 53 GPH.
    I prefer to keep it propped conservatively so just wondering what to expect after I blast and barrier coat.
  2. motoryachtlover, Jan 11, 2021
    #2
    motoryachtlover

    motoryachtlover Senior Member

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    I have a 95 Viking 54’ sport yacht (read MY). I have the 820s and my numbers are similar to yours. I run with a dinghy on the bow and usually atleast start out with full fuel and water is full. At 2050 I am right around 22 knots and burn 60 an hour with the genset running. I am propped conservatively as well. I cracked a case on one of the ZF 350s and ZF no longer makes them so I had both replaced with ZF 360s that come with a slightly lower gear ratio then the 350s so that has dropped my top end a touch. 27 knots is the best I will see. I am running 5 bladed Veems. I had my bottom blasted and re painted. I did not notice much difference. My experience thinks if you are reaching 2340 your bottom and running gear are pretty clean. I don’t think you will get much more than what you have. Mine won’t plane if it has barnacles on the wheels. Hope I am wrong but I don’t think you are far off. Others with more knowledge than me will respond.
  3. Lunderic, Jan 11, 2021
    #3
    Lunderic

    Lunderic Member

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    Thanks and I'm fine with the speeds I'm getting. When I pulled the boat the shafts were loaded with barnacles and props had a few. I always see them listed with a claimed cruise of 26 knots and top 30 but I never really expected that. I would imagine I'll get another 20-30 RPM with clean shafts/props but maybe not. Do you cruise at 2050?
  4. motoryachtlover, Jan 11, 2021
    #4
    motoryachtlover

    motoryachtlover Senior Member

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    Yes I do cruise at 2050. Boat seems to run better there. I am propped to reach 2400 fresh out of haul out. Wouldn’t surprise me if some experts think I am pushing to hard.
  5. Capt J, Jan 13, 2021
    #5
    Capt J

    Capt J Senior Member

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    It's impossible to say, because HOW dirty was the bottom, it's something that's impossible to measure. I soda blasted one yacht about 6 years ago, a 2007 62' Predator.......clean bottom before or after we made 2360 rpms full fuel/full water....... after soda blasting we did pick up 2-3 knots at 80% and WOT. 820's at 80% will burn about 60 GPH.
  6. Lunderic, Jan 19, 2021
    #6
    Lunderic

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    T'hanks, I'll report back in the spring when I relaunch. Personally I'm not worried about top and I'm unlikely to cruise much higher than 1950.
    1950/22 knots seemed to be a nice "sweet spot" for the boat. I would like to be able to turn 2350+ to make sure I'm conservatively propped.
  7. Capt J, Jan 19, 2021
    #7
    Capt J

    Capt J Senior Member

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    The rpm/speed that seem like the sweet spot now will be irrelevant after you soda blast the bottom and put paint on it. MAN's LOVE to run at 80% load as they don't make the brute torque the CAT's do and rely on HP and BOOST to keep even load factors.
  8. Lunderic, Jan 27, 2021
    #8
    Lunderic

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    Capt J Thanks so much for sharing your expertise. I know on previous boat I was underpropped and cruised at a little higher rpm and Pyro's were much lower. Would I be better of cruising at an RPM higher than 1950 with the 820's assuming all other issues are addressed? Surveyor stated the engines were at 80% at 2150. When I get time to use the boat in spring I'm sure I'll be more dialed in
  9. Capt J, Jan 27, 2021
    #9
    Capt J

    Capt J Senior Member

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    YES. Man’s don’t make the brute torque that cats do. The higher rpms, the motors make more boost, more hp, and don’t deal with as much varying load factors. Man recommends running at 80%, but I’d experiment a little and see where they seem to sound the best and run the smoothest......
  10. mapism, Jan 28, 2021
    #10
    mapism

    mapism Senior Member

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    God only knows how.
    With your engines, it's impossible to tell what the load is, at any given RPM.
    The best you can get is an estimate, based on actual fuel burn.
    But only as long as the boat has the equipment to measure it in real time, like the Floscan or Maretron flow sensors and instruments.
    And you should reverse the logic, sort of: check the fuel burn first (which tells you how many hp the engine is producing), then compare it with the fuel burn at 100% load at the same RPM (as reported in MAN specs).
    That's a half decent estimate of the load - anything else is just BS.

    Just as an example, if your boat would run exactly along the theoretical propeller demand curve, at 2000 RPM your engines should burn 28 GPH each (with an output of 573hp). At the same RPM and full load, they would burn 38 GPH each instead (with an output of 785hp).
    So, in this scenario, the engine load is 73% (calculated as either 28/36 or 573/785, which is the same, roundings aside).
    But if the boat doesn't have any real time fuel burn measurement system, that surveyor could only make wild guesses, at any RPM.
    Last edited: Jan 28, 2021
  11. Lunderic, Jan 28, 2021
    #11
    Lunderic

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    Mapism, Thanks and I agree. The only fact I have is that I burned 53 GPH for a 7 Hour cruise at 1950 with Generator running (probably 1 GPH). This trip started with full fuel and water. The only baseline I have now is about 26/Hour which seems to be dead on the MAN Fuel curve chart even though it had dirty bottom and barnacles on shafts. I will just have to use the boat and figure out what's best. I would like to add Pyro's to see what's going on as well. They seemed very valuable on last boat after I built a good baseline of data.

    On another note I really love this site and the willingness of the members to share expertise and experiences
  12. Capt J, Jan 28, 2021
    #12
    Capt J

    Capt J Senior Member

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    Pyros are a great idea. On the common rail displays they usually run 1225-1250F at 80% but I believe thats right after the turbo.
  13. motoryachtlover, Jan 28, 2021
    #13
    motoryachtlover

    motoryachtlover Senior Member

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    1996D5C3-85F7-4FFC-91F1-65C14B4F360C.jpeg 21668099-E7A4-4753-8A23-904369DACD58.jpeg
    Here is a picture of my pyrometer sensor (circled in red) and my pyro gauges(2 in the middle) that show my pyro temps. This is at cruise speed of approximately 2000 RPMs. Mapism in another thread recommended that I measure pyro temps from both banks of each engine. It would provide more info. I plan on doing this in the future. So think about that when you do yours.
  14. mapism, Jan 29, 2021
    #14
    mapism

    mapism Senior Member

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    Wow. If you are sure of that, you've got some cool running engines there.
    Though as I recall, in CRM engines the much higher numbers quoted by Capt J are due to the fact that the probe is before, not after the turbo.

    The suggestion of having the pyro on both banks is because it can allow an early diagnose of a faulty injector, in absence of any other reason why the readings shouldn't be consistent between each bank of the same engine.

    PS: just curious, what is the plate under the e/r ceiling in the first pic above meant for?
  15. Capt J, Jan 29, 2021
    #15
    Capt J

    Capt J Senior Member

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    Mapism the plate is polished stainless and acts as a mirror since the motors are so close to the ceiling, you can see down into the motor valley etc if there’s any leaks etc. also acts as a heat shield for the turbos.

    I’d be a little concerned as is because the pyro and boost is much lower on starboard engine in that pic. Are they running at the same rpm?
  16. motoryachtlover, Jan 29, 2021
    #16
    motoryachtlover

    motoryachtlover Senior Member

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    I think the plate is a heat shield. Just saw CJ’s post. I am not a mechanic so I look to you guys/others for answers. The engines have always had that difference. So that is not new. Come to think of it the starboard may not have quite as high of max load RPM as indicated by the helm VDOs. Before I had the turbos blueprinted if my memory is right the starboard took longer than the port to reach WOT. As always I want the forums input. But I am not worried about it as a true expert just did the 1000hr and other things and he sea trialed the boat twice and said she was running as she should.
    Last edited: Jan 29, 2021
  17. motoryachtlover, Jan 29, 2021
    #17
    motoryachtlover

    motoryachtlover Senior Member

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    2A130FB0-CF6B-4B25-855C-B20A5B003AD6.jpeg
    Here is a picture of the boost and pyro situation right after the turbos were blueprinted. The red marks were what it was before the turbos were blueprinted and the needles indicated what it was after they were blueprinted. I am not sure exactly what conclusions to draw from all of this but thought it might interest some of you.
  18. Lunderic, Jan 29, 2021
    #18
    Lunderic

    Lunderic Member

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    I was thinking about Turbocators to save real estate... Anybody have any experience or thoughts about these . I hadn't really thought about both banks on each engine but I would imagine that would be an added benefit

    [​IMG]
  19. Lunderic, Aug 13, 2021
    #19
    Lunderic

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    I realized I never followed up on the results. Bottom was soda blasted and painted, shafts and props cleaned. At 1950 Picked up about 1 kt to 23. What's interesting is it picked up 3 kts to 29 at WOT. I have been experimenting and a there seems to be a sweet spot at slightly over 2000 RPMs where she settles in at over 24 kts. (All are with full fuel and water). The boat seems much more responsive to the throttles (probably the barnacles on shaft and props). Works for me.
  20. motoryachtlover, Aug 13, 2021
    #20
    motoryachtlover

    motoryachtlover Senior Member

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    Good deal on the increase in speed. I did not get those results when I stripped my bottom paint. I have been told that the 820s seem to run better in the 2000 - 2100 rpm range (if propped conservatively). My boat does seem to run better in the 2050 range. The pyro temps stay the same and it seems to not struggle as much getting over the backs of the waves in a following sea. If your turbos have not been blueprinted you would likely get some more performance improvement. I did. Less black smoke and stronger hole shoot. Don’t recall any significant increase in speed.
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