[C320-list] Normal Performance Limits?

[Robert Seastream]

I cut all the leading addresses (for brevity), but left the authors  
signatures.

Brian (797), I have a 2002 with the 3GM30F Yanmar with a fixed three  
blade prop.  I typically run it at 2500-3000 RPM, easily making hull  
speed within that range.  Yanmar specifies 3200 as the continuous  
rating, 3600 as the max/one hour rating.  I've heard 2400 is best fuel  
economy (half gallon per hour) rating.

My knotmeter always reads lower than my GPS whether under sail or  
power, even around slack water times.  I've put it down to seaweed,  
barnacles, whatever restricting the paddlewheel assembly.  I've  
cleaned it at spring launch, to no avail and have gone with GPS  
readings since.  I'm not usually in such a hurry that speed knowledge  
matters.

Jack (947), is it the flex hose leading up to your pullout faucet/ 
sprayhead in the head sink that's leaking, or something further  
upstream from it?  Where are you located?

Our haulout is 10-13-08.  I love NH in particular, New England in  
general, but the sailing season is way too short.  With 11 years to  
retirement, I often (around fall, how odd) consider transferring as  
far south as would permit year round sailing, probably the Virginias  
or Carolinas.  I'd like to cruise the Bahamas on our own bottom  
someday.  Sigh.

Bob Seastream
Intuition # 906

>

> Sounds like the knot meter has a problem. If it was current, then at  
> some point in your travels you would have contrary current and your  
> knot meter would read higher than your SOG.
> You can calibrate the knot meter on a measured course or use the GPS  
> reading at slack tide conditions to get it reading more accurately.
> I can't comment on your water problem.
> Kirk
> #124
>>

>> Bert:
>>
>> I understand the analogy. But it seems to me that my knotmeter must  
>> be registering unrealistically low speeds when it always, and I  
>> mean always, shows one or two knots less than SOG.  And this also  
>> happens when running under power only. It seems doubtful to me that  
>> the difference is always current. Anyway, I consider this to be  
>> more a situation than a problem to be solved.
>>
>> The leaking fresh water connector under the head sink, on the other  
>> hand, is a problem.  I'm not getting any takers on that one.  
>> Apparently no one else has had the same experience.
>> jack
>> sure bet #947
>>>

>>> Jack,
>>>
>>> Using speed over ground is fine for determining when you'll get  
>>> some where.
>>> However, it tells you nothing about  how your engine is  running  
>>> as far as
>>> speed is concerned.  If an airplane is flying at 200  knots, but   
>>> has a 50 knot
>>> headwind, it's only going 150 knots over the  ground...same with a  
>>> boat only
>>> the variables are wind, current, tide, etc.
>>> Bert
>>> At Ease
>>> #442
>>

>>> Monte  & Bert:
>>>
>>> My 320 is now on jackstands for the winter after another  short  
>>> New England
>>> season. Now I'm eager to get in the water in the spring  to see  
>>> how the
>>> engine sounds at 3000 to 3600. It has always seemed to me  that it  
>>> "sounds"
>>> like it is content at the lower  rpms.
>>>
>>> Additionally, I have always thought that the knotmeter reading   
>>> was lower
>>> than the actual speed of the boat through the water. It  regularly  
>>> records
>>> speeds  in the 3, 4 and 5 knot range when I'm  certain I'm going  
>>> faster than
>>> that by any visual estimate. That's why I  pay more attention now  
>>> to the SOG
>>> when I'm intent on getting where I'm  going.
>>>
>>> And, while I have your attention, has anyone read my earlier  e- 
>>> mail about
>>> the leaking fresh water connector under the head  sink?
>>> Jack
>>> #947
>>>>

>>>> I  have owned mine since new in 1999 and have accumulated about  
>>>> 750 engine
>>>> hours. For most of those hours I ran it very conservatively at   
>>>> 2500 RPM's
>>>> and not quite 6 knots. After reading the posts about  exhaust  
>>>> elbow coking,
>>>> I pulled my ex. mixing elbow and found  it to be quite coked but  
>>>> nowhere near
>>>> plugged as some have reported. I  now run it at 3000 and it is  
>>>> actually
>>>> smoother at that RPM and  obviously faster at the expense of a  
>>>> higher fuel
>>>> burn. I think Yanmar  calls for max RPM of 3600 and max  
>>>> continuous of 3400.
>>>> I have  come to believe that diesel's like to work near their  
>>>> design load
>>>> limit and at lower RPM and load tend to run rich and the lower  
>>>> exhaust  gas
>>>> temperatures cause exhaust component coking. I don't know how  
>>>> they avoid
>>>> this with automobile diesel engines but they are not designed to   
>>>> be
>>>> continuous duty cycle as these small industrial and marine  
>>>> engines  are.
>>>> Monte
>>>> Laima #620
>>

>>>> I've had my 320 since it was new in 2003 and I have  never run my  
>>>> Yanmar 27
>>>> much more than 2600 or, rarely, 2800 rpm. With  a three-blade  
>>>> prop, I'm
>>>> probably doing about 6 knots over the ground.  My recollection is  
>>>> that
>>>> those rpms are about what the engine  mounting plate and the  
>>>> Catalina manual
>>>> suggest. Am I right or  wrong?
>>>> Jack
>>>> #947
>>>>>

>>>>> I didn't disagree with Rod. I reiterate,  these instrument  
>>>>> systems (tachs)
>>>>> are poorly calibrated and if you  normally run your engine at a
>>>>> conservative RPM and  then firewall it you may expect to see  
>>>>> smoke just from the higher
>>>>> exhaust gas temp burning combustion deposits out of the exhaust  
>>>>> system.
>>>>> That having been said I would agree that prop  pitch controls  
>>>>> max. RPM.
>>>>> Monte
>>>>> Laima  #620
>>

>>>>> I agree with  Rod, low RPM and black smoke with clean bottom &  
>>>>> Prop means
>>>>> it is overpitched. Should run at 3600 RPM at Max  throttle.
>>>>> Joe Barrett
>>

>>>>> These boats  also have notoriously inaccurate tach,s, something  
>>>>> else to check.
>>>>> Monte Laima #620

>>>>>  It sounds to me that you are over propped. You should be able  
>>>>> to get up to 3400 RPM.
>>>>> Can you adjust  the pitch on the Kiwi? If so, just reduce the  
>>>>> pitch  and you should be able to get
>>>>> up to the full RPM
>>>>> Rod  Boer Odyssey, #688

>>>>> I had my boat on the water  yesterday afternoon for likely the  
>>>>> last sail of
>>>>> the season. Although the wind was 15-20 knots on departure it  
>>>>> had dropped to
>>>>> near nil by the time the crew decided to head for home. To   
>>>>> ensure we
>>>>> arrived at the dock before dark I slowly  pushed the throttle to  
>>>>> maximum. On still
>>>>> water this gave me revs  at 2900, knots at 6.75 and plenty of  
>>>>> black smoke.
>>>>> On easing the throttle back to 2500 revs I was able to maintain  
>>>>> 6 knots and
>>>>> eliminate the smoke. I have a Yanmar 3GM30, a clean bottom and   
>>>>> a Kiwi
>>>>> prop.  Is this approximately normal?
>>>>> Brian  Amirault #797 Waltzing Bear, too