Josh pretty much restated my argument for repowering from an AT4 to a diesel. My main reasons were flatter torque curve and better fuel economy. The gasoline flammability issue had very little to do with my decision.
Punching into a seaway with an AT4 sucks. To generate the horsepower, an AT4 needs rpm's. The 1:1 drive just results in making bubbles. A diesel with a flat torque curve, a reduction gear and a big pitched prop takes a bigger bite without cavitating. Blenders are great for frozen drinks but not for driving a boat through waves. The admiral and I spent a couple hours punching dead upwind in a narrow channel one day in 3-4 foot seas and mid-teens on the nose. Sucked. Sitting back in Mandeville was a brand new 25 hp diesel and all the parts to repower. We just didn't have time to complete the swap before that trip. As for the original thread, Yanmar, I think, recommends 1 hp per 500 lbs displacement. I think that's a bit light. I seem to recall Nigel Calder recommends 1.5 hp per 1000 lbs. Dennis C. Touche' 35-1 #83 Mandeville, LA On Mon, Jan 12, 2015 at 5:46 PM, Jake Brodersen via CnC-List < cnc-list@cnc-list.com> wrote: > Josh, > > > > Great reply with good detail. I’ve had my share of bashing into heavy > seas and with just the engine, it can’t be tough going. My 30hp Yanmar > maintains a steady 3000 rpm, regardless of speed in these conditions. > Heck, we could be sliding backwards and the engine won’t slow down. Gotta > love diesel torque. > > > > I find it easier to motorsail when conditions get extreme. The ride is > easier and you do go faster. The heel stays fairly constant too. > > > > Jake > > > > *Jake Brodersen* > > *“Midnight Mistress”* > > *C&C 35 Mk-III* > > *Hampton VA* > > > > > > > > *From:* CnC-List [mailto:cnc-list-boun...@cnc-list.com] *On Behalf Of *Josh > Muckley via CnC-List > *Sent:* Monday, January 12, 2015 10:46 AM > *To:* DJ Hawk; C&C List > *Subject:* Re: Stus-List C&C 37+ engine size > > > > When you are experiencing heavy currents and can only go 3 kts to round > the mark. Is that 3 kts being measured by the gps or is it 3 kts measured > by the speed log? It sounds to me like it is 3kts by gps and if so then > from all of the other listers comments and my own experience a larger > engine would only allow you to proceed at 4kts. > > When people experience a mismatch between boat size and drive train > performance it is most often experienced in heavy chop. I believe there > are two main factors at work in these "under powered" cases. > > The first is the diameter of the prop. Smaller engines = smaller props = > less bite in the water and when things get sloppy the prop slips and > cavitates more. > > The second part is prop speed. In order to use a smaller engine to do the > same job the designers will gear it to gain mechanical advantage. The prop > will have to spin faster than its higher powered counterparts. Faster > prop=less bite and closer to cavitation. > > When these two factors are at play the speed log will slow > disproportionately to the gps speed. Everyone has probably experienced > plunging the bow into a breaker and seeing the boat speed come down. The > question is how long does it take go recover. These smaller props spinning > at higher rpm slip and cavitate more so speed recovery is longer. If the > next breaker gets to you before the speed recovers.... > > Remind me, your boat, Lolita?, has an A4 right? Is it direct drive? If > my recollections are correct then you have a couple of things that set your > experiences apart from what you could expect from a larger diesel powered > boat such as a 37+, 38LF, or a 40. Forgive me if my recollections are > incorrect. > > First is that the gas engines don't have as much low end torque so when > those breakers come and the boat needs to make up, the engine has a harder > time coming back up to speed. > > Second, the direct drive (1:1) means that right from the start the prop > has to spin much faster and an increase in load at the prop is directly > felt as an increase in load at the engine. There are no gears to help in > having less low end torque so the prop pitch is much less as well, again > meaning more cavitation. > > Third, being a shorter and lighter boat means that the breakers will cause > the boat to hobby-horse around a lot more and also push the bow off > requiring more helm. > > All of these factors make for a less comfortable ride and slower progress > in the thick stuff. > > Good Luck, > > Josh Muckley > S/V Sea Hawk > 1989 C&C 37+ > Solomons, MD > > On Jan 12, 2015 7:10 AM, "Danny Haughey via CnC-List" < > cnc-list@cnc-list.com> wrote: > > I think my point is; > > > > Where we sail there are some pretty good currents and the chop picks up > quite often. Sometimes, you have to make it home heading into both. > That's when you want the extra hp. We sometimes have guests that get a > little nervous when the conditions get exciting and we try to get them in > as quickly as possible. Sure, you can move along at hull speed in > favorable conditions but, the only time I'd be able to notice that the > stern dug in a few inches would be in the harbour, sometimes. We almost > never experience flat water and are typically dealing with a 3 to 4 knot > current. Sometimes it is our favor and usually try to time our trips so it > is. But day sailing, I don't really care as much. I sometimes could only > get 3 knots under full power trying to round a mark to get into a harbour. > That can be a little unnerving. > > > > Danny > > > > > > From my Android phone > > > -------- Original message -------- > From: Chuck S <cscheaf...@comcast.net> > Date: 01/11/2015 11:45 PM (GMT-05:00) > To: Danny Haughey <djhaug...@juno.com>,"CNC boat owners, cnc-list" < > cnc-list@cnc-list.com> > Subject: Re: Stus-List C&C 37+ engine size > > ". . . bigger is better. . . "? Is a bigger booty better? Will a bigger > anchor make my sailboat go faster? > > What helps sailing is "no engine". Light means flight. > > Research the brochures and look to buy a boat with the "designed right > size engine", not bigger. An upgrade would be a smaller diesel w a turbo. > Just sayin. > > > > Chuck > > > > > ------------------------------ > > *From: *"Danny Haughey via CnC-List" <cnc-list@cnc-list.com> > *To: *cnc-list@cnc-list.com > *Sent: *Sunday, January 11, 2015 7:54:45 AM > *Subject: *Re: Stus-List C&C 37+ engine size > > > > Ok well, I guess it is adequate then. I just tend to see 40 hp engines in > most 40 footers. > > > > Maybe not be the ideal and will be a bargaining point if it comes to that. > > > > Bigger is better in this instance I think... > > > > Thanks for the insights guys! > > > > Danny > > > > > > From my Android phone > > > > > -------- Original message -------- > From: allen via CnC-List <cnc-list@cnc-list.com> > Date: 01/10/2015 3:53 PM (GMT-05:00) > To: Robert Abbott <robertabb...@eastlink.ca>,cnc-list@cnc-list.com > Subject: Re: Stus-List C&C 37+ engine size > > > > Our 30-2 has 20 hp Universal and easily reaches hull speed in light to > calm conditions. Originally it was powered by an 18 hp Universal that > netted 16. > > > > Allen Miles > > s/v Septima > > > > *From:* Robert Abbott via CnC-List <cnc-list@cnc-list.com> > > *Sent:* Saturday, January 10, 2015 3:41 PM > > *To:* Danny Haughey <djhaug...@juno.com> ; cnc-list@cnc-list.com > > *Subject:* Re: Stus-List C&C 37+ engine size > > > > Danny: > Some say if you have one hp per foot of boat, you are adequately powered > for a sailboat. A 35 hp diesel in a 37+ seems adequate to me. > > > > Rob Abbott > AZURA > C&C 32 - 84 > Halifax, N.S. > > > > > On 2015/01/10 12:30 PM, Danny Haughey via CnC-List wrote: > > Hi Guys, > > > > I'm eyeing a 1989 37+ but it has a 35 HP universal diesel. That, seems > kind of small for a nearly 40' boat. doesn't it? > > > > Danny > > > > > ------------------------------ > > _______________________________________________ > This List is provided by the C&C Photo Album. > > > > Please donate to the C&C Photo Album to keep this list free for all > subscribers. > > > > Email address: > CnC-List@cnc-list.com > To change your list preferences, including unsubscribing -- go bottom of > page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > > > > > _______________________________________________ > This List is provided by the C&C Photo Album. > > > > Please donate to the C&C Photo Album to keep this list free for all > subscribers. > > > > Email address: > CnC-List@cnc-list.com > To change your list preferences, including unsubscribing -- go bottom of > page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > > > > > > > _______________________________________________ > This List is provided by the C&C Photo Album. > > Please donate to the C&C Photo Album to keep this list free for all > subscribers. > > Email address: > CnC-List@cnc-list.com > To change your list preferences, including unsubscribing -- go bottom of > page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > > > _______________________________________________ > This List is provided by the C&C Photo Album. > > Please donate to the C&C Photo Album to keep this list free for all > subscribers. > > Email address: > CnC-List@cnc-list.com > To change your list preferences, including unsubscribing -- go bottom of > page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > > >
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