AT4 is no different than any diesel when it comes to rpm’s, try running a
Yanmar as a direct drive with no reduction gear-you’d have the same problems. I
have a 2:1 reduction A4 in my 38 and it does as well as or better than all of
the reports I’m reading in these posts, although I will say I burn a little
more fuel to do it. Not enough to ever pay to compensate for the expense of
swapping to a diesel. The key is to match the prop to the engine and to run the
engine in the rpm range that maximizes the power/efficiency ratio. For my boat
with an A4 that means 2800 rpms (making about 23-25hp) at 1.1 gph which gives
me 6.4 knots with a clean bottom and smooth water. To punch into waves I put
the main up (with a reef if needed) and can make about 7 knots in any condition
that I have come across. That includes motoring into a 28 knot head wind with
4-6 ft waves that were about 20ft apart (water depth <15ft). Took a lot of
waves over the bow and got very wet on every wave, but went through it like a
champ! No engine that you could possibly fit in the boat would have pushed
through those waves, but the sail and engine combo....
James
S/V Delaney
1976 38
Oriental, NC
From: Dennis C. via CnC-List
Sent: Monday, January 12, 2015 8:40 PM
To: Josh Muckley ; CnClist
Subject: Re: Stus-List C&C 37+ engine size
Also remember Yanmar wants to sell more (i.e., bigger) engine. :)
Dennis C.
On Mon, Jan 12, 2015 at 7:12 PM, Josh Muckley <muckl...@gmail.com> wrote:
37+ = 16700lbs
1.5 per 1000 = 25hp
1 per 500 = 33.4hp
Remember the 3HM35F has funny ratings. IIRC they call it a 30hp engine but
at 3400rpm it's actual output is ~32hp and at 3600rpm it puts out ~34hp.
Josh
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
Sent: Saturday, January 10, 2015 3:41 PM
To: Danny Haughey ; 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
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