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post #1 of 7 Old 08-03-2018 Thread Starter
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Prop "sea Trial"

I thought someone might find this useful or interesting. Recently performed a “propeller Sea Trial Test” that I got from Bruntons, the maker of our 3 blade Autoprop. Our bottom had just been cleaned. 3 cylinder 32hp Westerbeke with a ZF Hurth V drive. 37’ double ended hull probably pushing 20,000# with all the stuff in her. Did two runs on a fairly calm river, one up and one down. 10-14knt wind on the beam, so speed might be a little high. This is the average of speed over water. Max rpm at idle is 3600 which matches the engine specs. I’ve sent the data to Bruntons for their opinion. Just curious what they think.

Rpm Speed (knts)
1000 2.3
1500 3.9
1800 5.0
2100 5.3
2400 5.9
2700 6.4
3000 6.7 (engine maxed out here, wouldn’t do more rpms)

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post #2 of 7 Old 08-03-2018
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Re: Prop "sea Trial"

Was this engine only?

Good post.
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Re: Prop "sea Trial"

You can get a fuel consumption /rpm curve to help decide best rev to run.
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post #4 of 7 Old 08-03-2018 Thread Starter
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Re: Prop "sea Trial"

yup, bare poles but probably got a little lift from the wind on the hull

where would I find fuel consumption /rpm chart? I'll look at the westerbeke spec but I don't remember seeing that.

btw, before getting the hull cleaned she max'd at 2700rpm. Only about 4 months sitting in the marina. Really surprised me to get 10% from the hull cleaning.

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post #5 of 7 Old 08-04-2018 Thread Starter
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Re: Prop "sea Trial"

Can't find a fuel consumption/rpm chart for my engine. Is there any rule of thumb for optimal fuel consumption? Like rpm at max torque? Some % of max rpm?

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Re: Prop "sea Trial"

Most engine data sheets include RPM /HP and torque and fuel consumption There may be a sweet spot.
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Re: Prop "sea Trial"

I look at it as 2 sweet spots.

One you like the fuel consumption...and can live with the speed.
One you like the speed..and can live with the fuel consumption.

From the figures you posted i would check consumption at 1800...5 knots is a decent working speed imo.

The great variable will always be conditions.
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