Fuel Consumption? 1985 Nanni Kubota 4 cyl 30 hp Boat Diesel

How much fuel does an old diesel burn?  Aboard Winterlude motorsailing we burn somewhere around  .7 gallons per hour at roughly 2600- 2800 rpms.  When we did the passage from the San Blas Islands to Cartegana, Columbia, there was very little wind and although the sails were up, we could barely claim to be motorsailing and we measured the .7 gallons an hour.  Keep in mind, Winterlude doesn’t go very fast under power – we’re a 12 ton boat with a 30 horsepower diesel — putt-putt, sip-sip!  Somewhere around 5 -6 mph is about the fastest we can go.  Frustrating when you’re cruising with lighter boats with bigger diesels!  But always being the tortoise isn’t all bad.  We could be REALLY fast like the power boat next to use at the fuel dock when we were bringing the boat south from Annapolis to Ft Myers, FL … as I went in to pay my $70 diesel tab, the meter for the power boat was up over several thousand dollars.  When I mentioned it, the cashier laughingly told me that was a small power boat!  Yikes.  This year at the fuel dock in Marathon, we watched as a beautiful yacht sat for hours fueling up – I want to say upwards of $5K … then the owner informed us that tank would get him from Marathon to Ft Lauderdale.  WHOA!!!!!  Obviously there are some very very rich people in the boating world!

Dolphins Play with the Bow on Passage, No Wind!

Dolphins Play with the Bow on Passage, No Wind!

Before last winter’s refit, we sailed from Providencia, Columbia to Port Royal Roatan, Bay Islands, Honduras.  The weather forecasts were continually wrong and the wind seemed like it was always on the nose.  Motorsailing for the better part of 5 days, we arrived in Port Royal with literally 8 gallons of diesel fuel!  Winterlude carries about 60 gallons of fuel in two tanks – one centerline and an added tank under the quarterberth, aft starboard.  In addition, we had 2 jerrycans full of diesel, which added another 10-12 gallons.  So a total of just over 70 gallons of diesel and we had 8 left at the end of the week.  Good thing I didn’t know that, I’d have been worried sick the entire last day!   Luckily that last day the wind gods finally smiled on us and we got to shut the diesel off and sail past Guanaja, Barbareta and on to Port Royal.

Winterlude does not have a tank fuel indicator gauge, we simply gauge our fuel by the manual dipstick in the tank inspection hole method.  Luckily there’s no reason to check it for awhile so that if the boat’s bouncing along the diesel doesn’t slosh out the top while we’re checking the levels.

Motorsailing in a Dead Flat Calm, Isla Mujeres to Charlotte Harbor, FL

Motorsailing in a Dead Flat Calm, Isla Mujeres to Charlotte Harbor, FL

Then on our Isla Mujeres, MX to Charlotte Harbor, FL passage, we had a dead flat calm passage … 4 days, blowing 20 when we sailed out of the anchorage at Isla Mujeres, then the wind switched and was finally taking us to the south coast of Cuba (our original cruising destination when we started that season, but we could never get the wind to get there, so it was ironic that the final sail of the season, FINALLY the wind wanted to blow us where we wanted to go six months earlier).   So we had to motorsail to get closer to the wind which ended up dying less than a half day later.

Friends on the SSB were worried we’d run out of diesel and advised we should put our jerry cans in the main tanks as soon as there was room – putting diesel into deck fill tanks under rough sea conditions can cause a multitude of severe problems – salt water in the tank being just one example.  So we filtered the jerry can diesel into the starboard quarterberth tank as soon as it would hold it.


Man O War Jellyfish Drifts By Winterlude in Dead Flat Calm, Motorsailing from Isla to Charlotte Harbor, FL

Man O War Jellyfish Drifts By Winterlude in Dead Flat Calm, Motorsailing from Isla to Charlotte Harbor, FL

So how’s your fuel consumption?  Share how many gallons you burn an hour – along with a bit of info on your diesel by leaving a comment below!  THX!  Jan



  1. Jim Shell says:

    Phantom is a Pearson 365 ketch, 9 tons. The auxillary is a Westerbeke 35Dthree, 31 hp. The engine uses abut 0.5 gph at 1750rpm, which is about 6mph, a nice and economical speed for our cruising. At 2400rpm the engine uses about 1.0gph and the speed is about 7mph. We have a motoring range of 500 miles at 1750 rpm and a range of 300 miles at 2400 rpm.

    • Nice! Thanks for the info. Wish our NANNI Kubota would go 6 at 1800 rpms. How much does your Pearson weigh? We’re both around 37 ft.

      • Jim Shell says:

        Phantom is a Pearson 365 ketch, 18,000 lbs. We repowered her in 2005 with a smaller engine (37hp down to 31hp) but used the v-drive and transmission to reduce the rpm (and increase the torque) to the propeller. We then increased the diameter and pitch of the propeller for the effect we enjoy. Our cruising is in the Texas ICW and the effecient engine rpm and speed is very nice. Pure sailing in the ditch is pretty much out of the question.

  2. Jim Shell says:

    I recently recalibrated my tachometer and determined that the tachometer was reading 128 rpm high. So My fuel usage is better than I reported. The data was an estimate from the engine manufacturer’s manual. I like these revisions.

  3. We have a Yanmah 27 hp on our Prout Event 34 catamaran. At 2500 revs I estimate that we use 1 litre per hour. On calm seas we travel about 6 nm in that time.

    • We have a Pearson 365 ketch with a 31 hp Westerbeke. We use about 1/2 gallon of diesel per hour at 2000rpm (3000rpm max) for 5.5 – 6 kts.

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