Crusing RPMs on a Cummins 210

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Crusing RPMs on a Cummins 210

Postby ajgraham@sbcglobal.net » Mon Sep 17, 2018 5:58 pm

My boat is a 1990 GB 32 (829) with a Cummins 210. Everyone at the marina has been telling me to cruise at no more than 1,700 RPMs but in the Cummins engine manual the cruising RPM is listed as 2,300. Now I understand at 1,700 I burn about 3 -4 gal. an hour and the manual indicates at 2,300 RPM the burn rate is 10 gal per hour. The manual indicates the top RPM is 2,400 RPM. Any insight is greatly appreciated.
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Re: Crusing RPMs on a Cummins 210

Postby Cruising » Wed Oct 31, 2018 8:11 pm

We cruise at 1600-1700 rpm in our 42E. We have twin Cummins 210’s
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Re: Crusing RPMs on a Cummins 210

Postby Cruising » Sun Feb 24, 2019 12:15 pm

Max torque on a decidedly is typically 75% of max rated rpms. So based upon this calculation 1800 RPM would yield max torque. But since our boats are a semi displacement hole and we typically run in displacement mode the max torque is not required as we don’t lift the boat to plane.

We have a 42E w/ Cummins 210’s as well and cruise at 1650 rpm. At this speed be burn 4-4.5 gph. Upping the rpm’s by 100 ever so slightly lisp fits the boat (pre plane) and increases the burn rate to 5.5-6.0 gph.

At 1800 RPM the boat is cruising at 9 1/2 kn, the bow lifts slightly and just staring to plane. It takes a lot of energy now to lift this 20 ton boat and the max torque required @1800 rpm is at the perfect spot. Just a coincidence? Based on my experience with I Grand Banks, I think not. Probably the most well-designed boat I have ever had the pleasure to own.

When we purchased our boat about a year and a half ago and had a Cummins rep do the survey. His comment about this engine and rpm speed was illuminating to me. The 6BT5.9 210hp engine is a proven workhorse and since the 210 hp is not a “pushed” (shaved head and intercoolers, etc) engine you could actually run this engine full throttle 24 hours a day without issue. While I don’t operate our boat in this manner it’s good to know that one can.
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