[C320-list] Engine noise

[Kirk McCullough]

Jeff

This makes sense to me. Plus at higher RPM you get there faster and run up 
fewer engine hours.

Kirk McCullough
Boomerang #124

----- Original Message ----- 
From: "Jeffrey Hare" <Catalina at thehares.com>
To: "'C320-List'" <c320-list at catalina320.com>
Sent: Tuesday, July 17, 2007 6:49 AM
Subject: Re: [C320-list] Engine noise


> Hi Brian,
>
>  As usual, I summarized in a way that isn't completely accurate.  There 
> are
> a lot more factors, and many of them I don't yet understand.
>
> Specifically, I should have said that motoring to a *specific destination*
> at 1000RPM will typically take more fuel than motoring to that same
> destination at 2900RPM.  The exception here might be if you have an 
> autoprop
> that self-pitches, or a Gori and can motor in overdrive, but the research 
> I
> was reading didn't address that.
>
> I'm still studying this, but from what I understand so far, if you 
> decouple
> the engine from the prop and just look at fuel consumption over the RPM
> range, lower RPM burn less fuel than higher RPM as you would expect.  But
> that doesn't tell the story.
>
> When looking at HP transmitted to the water, lower RPM burn more fuel per 
> HP
> transmitted to the water because (as I interpret it) the propeller curves
> and engine curves  are only optimal around the engine's "sweet spot". 
> Which
> is ~2900+ish for the Yanmar 3GM.  As you go outside that sweet spot with
> lower RPM you're burning more fuel/HP transmitted to the water.
>
> So... It seems that you do indeed burn less fuel at lower RPM, but getting
> to a specific destination may require a little more fuel if you motor 
> there
> at low RPM.
>
> This may account for why some people say the yanmar burns ~.5 gal/hr and
> others say they use ~.7 gal/hr.  Different props, different RPM used on
> average, etc...
>
> If anyone out there has read the prevailing research and understands it
> better, chime in.  :)  Typically you find this research when attempting to
> compare the efficiency of diesel/electric vs. plain diesel drive systems.
>
> -Jeff
>
>
>
> -----Original Message-----
> From: c320-list-bounces at catalina320.com
> [mailto:c320-list-bounces at catalina320.com] On Behalf Of Amirault Family
> Sent: Monday, July 16, 2007 5:51 PM
> To: c320-list at catalina320.com
> Subject: [C320-list] Engine noise
>
> Jeff:
>
> The diesel giving higher consumption at lower revs IS counter intuitive.
> Could you give a brief overview of the theory? It has me curious and an
> understanding my lead me to begin using higher revs.
>
> Brian Amirault
> 797 Waltzing Bear, too
>
>
>
>
>
>
>
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