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Fuel consumption a linear function of engine RPM?

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
If worried about burning the minimum fuel, I slow down to where we produce very little stern wake, or about6 kts. We normally motor at 7.0, but there is a noticeable wake coming up behind the transom. If viewed from broadside, that is about the point where the sine wave starts at the bow, rises some, and dips in the middle of the boat's profile and rises again to a high point at the stern.

When we have a lot more wind-provided "horse power" to put into the hull, we have held onto 10 kts for hours, in open ocean, running in 24 kts true. That put some occasionally back wash splashes up thru the cockpit drains. Easy sailing and a gratifying reason to own an Olson.
:egrin:
 
Last edited:

goldenstate

Sustaining Member
Blogs Author
If worried about burning the minimum fuel, I slow down to where we produce very little stern wake, or about6 kts. We normally motor at 7.0, but there is a noticeable wake coming up behind the transom. If viewed from broadside, that is about the point where the sine wave starts at the bow and dips in the middle of the boat's profile and rises again to a high point at the stern.

When we have a lot more wind-provided "horse power" to put into the hull, we have held onto 10 kts for hours, in open ocean, running in 24 kts true. That put some occasionally back wash splashes up thru the cockpit drains. Easy sailing and a gratifying reason to own an Olson.
:egrin:
At what RPM are you operating when you think you have achieved optimum engine efficiency? Does it compare well to the maximum torque point on the curve for your Beta or some other manufacturer-provided data point?
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
At what RPM are you operating when you think you have achieved optimum engine efficiency? Does it compare well to the maximum torque point on the curve for your Beta or some other manufacturer-provided data point?
I used to cruise our Universal M25XP at the factory suggested "cruising rpm" of about 2400 to 2600 rpm , IIRC.
The Betamarine has a similar spec, but then it's also based on a Kubota engine.
That being said, you have to have the prop pitched for that speed also.
 

footrope

Contributing Partner
Blogs Author
Depends on what waters you are sailing in. In the Puget Sound, max miles/gal is achieved by drifting with the tide with the engine off.
If you put up a sail or two, sometimes you can go faster with the engine off. But sometimes faster is in the wrong direction.
 
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