Click for YFYS Click for Nordhavn Click for Yacht Lettering Click for Walker Click for Lurssen

Propping a 58 Viking

Discussion in 'Viking Yacht' started by incoming, Feb 1, 2022.

  1. incoming

    incoming Member

    Joined:
    Jan 14, 2021
    Messages:
    51
    Location:
    Deale, MD
    My new to me 1998 58 Viking is currently propped with 30x46x4 wheels

    the motors are 1200hp Mans, 2:1 zf gears

    The PO reported the original props being damaged by electrolysis, and the boat being about 2 knots slower after getting new propellers.

    According to my research and confirmed by Viking, the original wheels were 31x46x4

    the boat makes almost 2400 WOT loaded. So I’ve got a little bit of room to prop up, maybe.

    wondering if it’s worth the expense to have 31” wheels made for it? I expect I’ll have to come down an inch in pitch from the original spec to account for the age of the motors and all the stuff on the boat.
    So I’d be going up an inch in diameter and down an inch in pitch. Is that likely to net me a noticeable improvement?

    I hate leaving any performance or efficiency on the table, but also have plenty of other things to spend money on…
  2. RER

    RER Senior Member

    Joined:
    Jan 20, 2009
    Messages:
    1,472
    Location:
    Newport Beach CA
    That’s gonna be a considerable stack of dough just to see what might happen. What about adding some cup to your existing wheels at the next haul out. You can get feedback from the prop shop once they’ve got ‘em.
  3. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    10,717
    Location:
    Satsuma, FL
    Diameter makes a world of differences that most folks can not apprehend.
    A quality (real world) can reason it out but why try to re-invent a wheel, the factory has already done so much for you.
    You think these guys just guess and install a set of wheels for you to live with?
    I'm sure hundreds of hours were spent to get a good, starting sized wheel installed to deliver.

    What is the factory spec?? Call them up and ask about improving, per your use what way you can go.
    BUT, The factory spec is always where to start from.
  4. RER

    RER Senior Member

    Joined:
    Jan 20, 2009
    Messages:
    1,472
    Location:
    Newport Beach CA
    Almost anytime I’ve seen diameter added to props the result is overloaded motors. Of course as Ralph points out it depends on where you start from.
  5. incoming

    incoming Member

    Joined:
    Jan 14, 2021
    Messages:
    51
    Location:
    Deale, MD
    So in my case I’m currently 1” diameter below factory spec, and the pitch is the same as spec’d. I have no idea why the PO did this, or if it was even on purpose. The question is whether I’ll get significant (or even noticeable) improvement by adding an inch of diameter.

    The Viking engineer advised that the factory spec prop often needs to be pitched down slightly on a boat of this age to account for added weight (I have a tower and run with a dinghy on the bow) and the engines tiring a bit.

    So, everything I’ve read suggests diameter is critical for efficiency and to swing the biggest wheel the boat can handle (clearly 31” will work since that’s what was spec’d). But if I go up an inch in diameter, but have to drop 1-2” in pitch to keep from overloading, am I really gaining anything?
  6. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,115
    Location:
    Fort Lauderdale
    No, just add pitch to your existing wheels.
  7. RER

    RER Senior Member

    Joined:
    Jan 20, 2009
    Messages:
    1,472
    Location:
    Newport Beach CA
    Are those 2300rpm motors? You say you’re almost at 2400 so that’s less than 100rpm to burn. If that’s the case there’s no way I would increase prop diameter. But based on your last post you look like you’ve already made up your mind. Good luck.
  8. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    10,717
    Location:
    Satsuma, FL
    I'm into diameter and blade area. I have lots of past personal projects where I have proved this to myself.
    A little more blade surface = more traction.
    You just want to eat up 100 rpm, ad pitch.

    Do you have a set of spare wheels? Do you need a set?

    Your operating well now and in no hurry.
    Just keep a new set of wheels on your x-mas list and ask around the real prop shops. They may share some thoughts and a loaner prop set to experiment with.
  9. mapism

    mapism Senior Member

    Joined:
    Aug 9, 2008
    Messages:
    1,716
    Location:
    Sardinia
    Let's say you do, and you get those 2 knots max back. That's what, 1 knot at cruising speed? Probably less.
    I wouldn't lose any sleep over that, let alone money.
    And that's without considering if you must shorten the pitch to avoid overload, 'cause in that case you can forget getting back the 2 lost knots.
    In fact, you said that you're almost making 2400, and 2350 is what you should really aim at, not 2300.
    So, the room you can actually play with is how much, 30 rpm?
    Be happy with what you've got, I say.
    Most 24 years old engines around would tell you they are envious of yours, if they could talk!
  10. incoming

    incoming Member

    Joined:
    Jan 14, 2021
    Messages:
    51
    Location:
    Deale, MD
    Good input all. This was the way I was leaning but it’s good to talk it through. I only got to run the boat a few trips before I had to put her on the hard last year. So I’m going to at least run her for a full season and monitor WOT RPM and fuel burn through the season with varying bottom growth, etc. Then, as suggested, will consider a 2nd set in the future (current props were the PO’s spares he out on when the first set were ruined by electrolysis). Also, fuel burn has seemed a little on the high side compared to the curves, but that’s just measuring it the old fashioned way running it and filling up a couple of times. A full season of use will provide more data to know where i am.
  11. motoryachtlover

    motoryachtlover Senior Member

    Joined:
    Jan 29, 2007
    Messages:
    503
    Location:
    smithfield, VA
    Don’t know if this comparison will help but with a 1995 54 Viking MY with 820 Mans with a dinghy, etc on the bow I burn 60 gallons an hour with genny at 2050 RPMs. This is at 21 knots or so. I had what I believe to be original wheels on it and replaced those with 5 bladed Veems from Black Dog in MD and I now turn 2400 on my best day (winter (cool temps) and fresh bottom). In the summer with shark skin on the wheels and higher temps I will lose 50 RPMs. I wouldn’t touch your props. You will lose your cushion. I am sure others will disagree but slightly underpropped I will run at the upper end of the cruise RPM knowing my engines are not stressed. I have been told more than once that properly propped MANs like being run at the upper end of the cruise RPM. If you want to help your performance my best money was spent blueprinting the turbos. You could feel the difference and see the difference (much reduced smoke). Of course that is assuming yours need it which based on my experience they probably do.
  12. incoming

    incoming Member

    Joined:
    Jan 14, 2021
    Messages:
    51
    Location:
    Deale, MD
    yeah I suspect you are right - there is documentation of at least 2 of the 4 turbos being replaced in the last several years but my man guy suggests baselining all 4 of them. Do you mind sharing what you paid roughly per turbo, who did it, and if you were happy with them (sounds like you were)? Can PM me if preferred.

    got my best fuel burn data on a round trip to VB late fall - about 0.3-0.31 nmi/gal at 2000 RPM cruise, which was 23-26 kts depending on wind and current (mostly 23-24). Suspect it would come down a bit in real offshore conditions, vs the bay.
  13. motoryachtlover

    motoryachtlover Senior Member

    Joined:
    Jan 29, 2007
    Messages:
    503
    Location:
    smithfield, VA
    No I don’t mind sharing at all. I will have to go home and look up the invoice. I don’t believe the invoice listed the blue printer but I am pretty sure he was in and around Palm Beach. Yes I am happy with the work. I will try to look it up tonight and get back with you.
  14. DOCKMASTER

    DOCKMASTER Senior Member

    Joined:
    Feb 26, 2012
    Messages:
    1,075
    Location:
    Ketchikan, Alaska
    You could always contact Veem, fill out their boat info/specs form and then see what prop diameter and pitch they recommend. You may find they don't recommend much different then what you already have. But as others have suggested, sounds like you're in a pretty good range already. Likely lots of other areas to spend those boat bucks :)
    Capt Ralph likes this.
  15. incoming

    incoming Member

    Joined:
    Jan 14, 2021
    Messages:
    51
    Location:
    Deale, MD
    actually did this a few days ago. Waiting to hear back. There’s an old power and motoryacht article floating around talking about propping this vintage 58 with some exotic props and getting a big performance boost, but the engineer at Viking wasn’t familiar with that particular history.
  16. motoryachtlover

    motoryachtlover Senior Member

    Joined:
    Jan 29, 2007
    Messages:
    503
    Location:
    smithfield, VA
    Back in 2014 the cost per turbo was $2,515.00. No freight or labor to remove and replace. I am not sure who did it. It is not listed on my invoice but I believe it to be DMS in West Palm Beach. I did not see a 2 knot difference about a knot faster, with much better hole shot, higher boost and lower pyro temps.
  17. incoming

    incoming Member

    Joined:
    Jan 14, 2021
    Messages:
    51
    Location:
    Deale, MD
    Ok cool. That’s super helpful. Thank you
  18. motoryachtlover

    motoryachtlover Senior Member

    Joined:
    Jan 29, 2007
    Messages:
    503
    Location:
    smithfield, VA
    Your welcome. Keep us posted
  19. LAM

    LAM New Member

    Joined:
    Nov 8, 2007
    Messages:
    3
    Location:
    MD
    Call Gene at Black Dog props over on Kent Island, used him for years and he is the best around and does a lot of Vikings props and Weavers. Ideally you want the engines to turn up to less than 50 rpm over rated WOT.

    Taking my Veems over to him to add a bit of cup to pick up a little more speed at cruise as think old owner had it slightly under-propped.

    Who are you using on your MANs? Think we met down at HHS on the fuel dock, we have a 2000 47 Viking

    Ryan
  20. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,115
    Location:
    Fort Lauderdale
    man’s are faster when they’re slightly under propped. Having them turn 2350 or even a little more is faster than barely hitting 2300. Mans rely on boost to make power and lack the brute torque of cats, faster you spin them, the more power they make both at cruise and wot. I wouldn’t add anything unless you’re over 2400