1982 Cherubini w 12 HP Yanmar - Hull Speed?

Discussion in 'The Cherubini Hunters' started by polarbear, Jun 25, 2018. Add this thread to a FAQ

  1. polarbear

    polarbear

    Joined Sep 16, 2014
    18 posts, 0 likes
    Catilina 22
    US Onekama
    Bought a 1982 Hunter Cherubini with a Yanmar 12 HP engine. Have not sailed her yet. Just wondering what cruising speed might be if just motoring. Thanks
     


  2. Ron20324

    Ron20324

    Joined Jan 22, 2008
    6,836 posts, 856 likes
    Beneteau 323
    US Annapolis MD


  3. polarbear

    polarbear

    Joined Sep 16, 2014
    18 posts, 0 likes
    Catilina 22
    US Onekama
    What I'm wondering is if 12 HP is enough to push boat along at say 5 knots?
     


  4. MikeHoncho

    MikeHoncho

    Joined Dec 28, 2015
    294 posts, 119 likes
    Laser, Hunter H30 Standard
    Un Tacoma
    What size is your boat?
     


  5. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,590 posts, 2,533 likes
    O'Day 19
    US Littleton, NH
    weight, waterline length, bottom and keel shape all determine how hard your boat is to push. 12 HP should push a typical 30 footer at about 5-6 knots or better.

    -Will (Dragonfly)
     


  6. HarrisOutdoors

    HarrisOutdoors

    Joined Jun 8, 2018
    32 posts, 10 likes
    Hunter H27
    Wanderer US Bay St Louis, Mississippi
    9.9 yamaha outboard will push my 1980 Hunter Cheribuni 27 at 6kts which is just under hull speed (6.2kts)
     


  7. MikeHoncho

    MikeHoncho

    Joined Dec 28, 2015
    294 posts, 119 likes
    Laser, Hunter H30 Standard
    Un Tacoma
    My 78 H30 with a Yanmar 2gm20f (16hp) will push mine 6 knots at the top end of rpm limit.
     


    Last edited: Jun 26, 2018
  8. Roland5048

    Roland5048

    Joined May 12, 2004
    1,184 posts, 381 likes
    Hunter Cherubini 30
    US New Port Richey
    My '77 h30 came with a YSB12 Yanmar, 12 hp. Was twenty years old at the time. Hours unknown. You probably have the YSM12. Not sure what the differences are. After tranny rebuild and some engine redoing, (not a total rebuild) could push her 5 - 5.5 kts. Not so much into a strong wind or current. Those 12 horses may only be 8-10 at the prop. Replaced with a 3ym20, (21 hp) 10 years ago. Can do 6-6.5 kts and over 5 in a strong breeze or current at 3K RPM. Max is 3600. Not suggesting you do that. Only mentioned for comparison purposes. Also, 2 or 3 bladed prop? Let us know what you find out when you take her out.
     


  9. Roland5048

    Roland5048

    Joined May 12, 2004
    1,184 posts, 381 likes
    Hunter Cherubini 30
    US New Port Richey
    Afterthought: I'm assuming you also have a h30 as they put the 8 hp YS series engine in the h27.
     


  10. pateco

    pateco

    Joined Aug 12, 2014
    2,201 posts, 643 likes
    Hunter 31 (1983)
    US Pompano Beach FL
    My 1983 H31 has a 2gm 13hp Engine moves her just fine.
     


  11. polarbear

    polarbear

    Joined Sep 16, 2014
    18 posts, 0 likes
    Catilina 22
    US Onekama
    Sorry. Left out that its a Hunter 33. If the engine is too old or bad in some way, can it be replaced by the Marina boat yard?
     


  12. Benny17441

    Benny17441

    Joined May 24, 2004
    5,744 posts, 415 likes
    CC 30
    US South Florida
    The Cherubini models came in various boat lengths, 25', 27', 30', 33' and 37'. The longer the waterline the higher the speed for a displacement hull. While a 12HP might propel a 25 or 27 beyond its theorical limits it would hardly be adequate for the larger models. Boat speed can be measured in two ways, over water or over land (bottom). Speed over water gives an indication of how efficient the boat is moving while speed over land is an indication of how fast you are moving towards your destination. When measuring speed conduct two runs one upwind and the other downwind and average out the results to try and eliminate the effect of currents and wind. Boat speed over water is mainly used to compare performance while boat speed over land is more used for cruising in calculating ETA, fuel range, distance travelled, velocity differential between tacks and navigation data.
     


  13. Benny17441

    Benny17441

    Joined May 24, 2004
    5,744 posts, 415 likes
    CC 30
    US South Florida
    Sorry missed your reply to boat size. I would say a 33' with a Yanmar 12 is going to be somewhat underpowered. I would estimate top motoring speed over water at 4.5 knots.
     


    MikeHoncho likes this.
  14. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,590 posts, 2,533 likes
    O'Day 19
    US Littleton, NH
    This quote from a yacht brokers sight for a 2005 Hunter 33, "Yanmar type 3YM30 engine with 28 hp (20,58 kW), built 2005 with number E-03380, sail drive, speed approx. 6 knots"

    - Will (Dragonfly)
     


  15. Benny17441

    Benny17441

    Joined May 24, 2004
    5,744 posts, 415 likes
    CC 30
    US South Florida
    The question is about a 1982 33' with a 12HP engine; what's the point?
     


  16. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,590 posts, 2,533 likes
    O'Day 19
    US Littleton, NH
    The question was whether 12 HP was enough to push the boat at 5 - 6 knots. The quote I posted shows that a Hunter 33 with 28 HP goes about 6 knots. That seemed relevant. The difference in year probably makes a difference in effect of force to speed, but I would think they would be within the same ball park. If it takes over twice the horse power to move a 2005 Hunter 33 at 6 knots, what speed will an '83 Hunter 33 move with its motor?
    Frankly, 28 HP is a pretty good sized motor and I can't believe that it doesn't push the Hunter beyond her hull speed. All this speculation and comparison is fine for getting an idea, but the only way to know for sure is to take her out and try it. My 19' sailboat achieves hull speed with only 3 hp. However, Mariners are very light boats with shallow draft. There is not a lot of resistance.

    -Will (Dragonfly)
     


  17. David in Sandusky

    David in Sandusky

    Joined Nov 8, 2007
    1,160 posts, 186 likes
    Hunter 27_75-84
    US Sandusky Harbor Marina, Lake Erie
    Our boat yard swapped out the original SB8 for a 1GM10 in our ‘77 h27. But you need to talk to your yard to find out if they are capable and have the experience. Some yards would not.
     


  18. kloudie1

    kloudie1

    Joined Nov 6, 2006
    8,287 posts, 753 likes
    Hunter 34
    US Mandeville Louisiana
    Most of the few Cherubini 33 hunters I knew had 20 HP or so..either a QM or a GM engine.. They did fine with that power .. I would think 12 HP would be underpowered for that boat. That being said, if the engine is only used for in/out marina and not on very rough days, it would be adequate.
     


  19. FastOlson

    FastOlson

    Joined Apr 8, 2010
    1,082 posts, 151 likes
    Ericson Yachts Olson 34
    US Portland OR
    Hull speed potential is a good (calculated!) starting point. After that you assess your particular boat's resistance to moving thru the water. Basically, the parts of the design that contribute to more interior "living" room slow the boat down and will require more HP to power it.
    It's best to remember that some hull designs are intrinsically more slippery than others. While a few Hunter hulls, like the original 25, were transitioned from faster-performing hulls, most of the shapes have been more dedicated to interior comfort.
    Your H-33 is long enough to maintain 6.5 continuously in smooth water. Your engine was probably a bit marginal when new, but still adequate. A new sailboat that size would have an aux. engine rated from 23 to 28 hp.
    Part of that is also because of evolving owner desires... for amenities... like a horsepower-consuming large alternator. :)
    For one data point, I have done a multi day delivery on a 33 foot offshore performance boat with the Yanmar YSM-12. That particular design (Yamaha 33) is a very slick hull form with a very efficient engine installation. We could do 6 kts for 24 hours in the ocean with that engine. It's a real good motor, even tho the 12 HP is likely closer to 10 HP at the shaft, as has been pointed out. It was also unexpectedly quiet considering that it's a big single cylinder. Parts are harder to find nowadays, but that's a challenge for most engines of that vintage.

    Further, and no, you did not ask... but... be Really sure that your boat has a correct size and pitch propeller. Most new owners take for granted that whatever piece of cast bronze is down there (out of sight) under the water must be OK, because it came from the factory or maybe some prior owner. This is seldom true.
    And getting whatever amount of HP you have delivered efficiently to the water is more than 50% of the problem.

    Does your boat have a "little bit" of slime or growth on the bottom? There goes another half a knot.

    Good luck in finding some more knots!
     


    Will Gilmore likes this.
  20. Scott T-Bird

    Scott T-Bird

    Joined Oct 26, 2008
    3,900 posts, 894 likes
    Starwind 27
    US Barnegat, NJ
    That HP is not enough for your boat. In the old days, they must have underpowered and/or the original buyer didn't want to pay for an upgrade.
    Onekama looks like a beautiful location! That's in the heart of arguably the most pleasant shoreline in the country! Are you on the eastern end of Portage Lake? If you have a 3-mile run by engine to get out into Lake Michigan, crawling along at less than 5 knots on a flat surface may seem really tedious. By now, you must have some knowledge about the top end speed with the old engine. I'd be surprised if you reach anything close to hull speed and I suppose that is why you are asking the question. A new engine and prop should be sized appropriately to reach hull speed at cruising rpm in my opinion.
    A new engine will give you higher amps for charging and heat exchange for hot water, which you may not have from your current engine. If you love your Cherubini, (and why wouldn't you? :)), you're probably thinking about re-power. If you have the wallet for it, then you won't be sorry.
    Check the footprint of the mounting feet for width and length and compare it to new engine models. You need the stringers/rails to accommodate the new footprint.Width may be more difficult to modify than length. Check all the clearances in the engine compartment. I had to modify mine and it was doable but led to a few minor complications. I did the compartment modifications but the yard did the engine install. Have it done by an authorized dealer of Yanmar or other brand that you select for warranty purpose. Remember that you probably can't move the engine back if the shaft position limits positioning. My new engine was 2 inches longer and the front end of my compartment had to be adjusted because I couldn't push the rear of the transmission any further back than original install due to shaft limitation.
     


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