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Old 04-09-2016, 01:28 PM   #1
City: Owensboro
Country: USA
Join Date: Apr 2016
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Best cruising/fuel economy

Fairly new to 2007 430 Mainships Trawler with 540hp Cummins. Requesting info on best fuel economy/cruising speeds. Thanks

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Old 04-09-2016, 02:57 PM   #2
djmarchand's Avatar
City: Essex, Ct
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Vessel Model: Mainship Pilot 34
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Here is a test performed by Cummins on that boat with the twin 540s:

Scroll down until you find the 43/45 numbers.

As you can see, fuel economy improves as rpm and speed drop, all the way to idle. So you have to be more specific. I don't think you want to run at 5 kts at idle even though you are getting 5 NM/gal..

Also you probably don't want to run lower than 1,200 rpm for any length of time to keep the engine loaded decently. See the tedious/nauseous thread "Under loading" for enlightenment on this issue.

Finally, those tests are somewhat optimistic as they are done with limited fluids, people and gear. You can make an approximate adjustment by taking your actual wot speed, ratio that to the Cummins wot speed and apply that factor to all of the data.


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Old 04-09-2016, 03:19 PM   #3
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I probably would not run it below 900-1000 rpm for long distance cruising, especially if engines are not yet broken in. If not broken in, I'd run as much as you can around 2000-2200 and get the rings seated in.

If already broken in, 1000rpm is fine, but a couple times a day run it up to 2200 for maybe ten minutes.

That boat has A LOT of hp for it's size.
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