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Catalina/Capri 25/250 Sailor's Forums

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Miles per Gallon

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Bob3589
1st Mate

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31 Posts

Initially Posted - 08/19/2003 : 14:32:19

I will be taking my 83 TR/FK from Mobile, AL up the Tombigbee waterway to Tennessee (450 miles)in a few weeks and part of my preparation is determining how much gas to take for motoring between marinas that have fuel. Some distances could be 75 to 100 miles. I'll use sail power when possible but need to know approx miles per gallon, say at half throttle, normal/average current and water conditions. I have a 2003 Honda 8HP 4 stroke, elec start. Has anyone done a test or have a fairly accurate estimate ?? Thanks.

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 08/19/2003 : 15:42:01

As best I could determine, we've done about 1/2 gallon per hour at about 5 knots thru the water, so 100 miles would require a MINIMUM of 10 gallons. How about two six-gallon tanks in addition to your three-gallon OEM tank. BTW, Honda's six-gallon is much better than Tempo's (stronger, tighter, better guage, etc.), but costs about double. Since either can be stored upright, you could possibly lash one to the inside of the transom between the seats...

For economy, watch your speed... When you start to create a stern wake, you're pushing too close to hull speed, dragging the transom, and wasting fuel. 5-5.5 knots thru the water (independent of currents) is plenty under power.

Have a great cruise!

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

Edited by - dave bristle on 08/19/2003 15:48:38

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ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 08/19/2003 : 16:37:31

You say you're gong UP the waterway?

Be sure to factor any contrary current you will be facing into Dave's ballpark numbers.

If you have a 1kt contrary current, you'll need about 20% more fuel to make the distance... as you will only be making 4 kts "over the ground".

Of course, at 6 kts current, you'll never arrive. ;>0

Currently maintaining two holes in the water...'77 Venture 23 and new to the family,
'78 Catalina 25

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JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 08/19/2003 : 17:18:40

I have the Honda 8 hp 4 stroke. On my recent vacation cruise I travelled 80 miles (offshore) on 8 gallons. One day I had a good beam reach and motorsailed 40 miles on 3 gallons. Coming back it was flat and calm and it took about 5 gallons to go the 40 miles. I sailed a total of 200 miles in 2 weeks and used about 15 gallons total.

The Honda has a very economical idle jet in the carb. I try to keep the throttle below about 1/3. This is a very calm RPM that pushes me in flat water to about 5.5 knots. One time I opened it up and motored at 6.5 knots 33 miles on > 6 gallons (ran out while anchoring) so be carefull if you push the speed up.

I have the Honda tank in my lazerette. It is a 6.5 gallon. I have a 2nd emergency reserve 3 gallon tank right below it. All you have to do is move the fuel line to the 2nd tank. I also carried a 5 gallon tank in the V-Berth for refilling.

<img src="http://www.indiscipline.org/cat25/pictures/icon.jpg" border=0>Indiscipline 1978 FK #398

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JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 08/19/2003 : 17:19:37

everything I quoted is in nautical miles.

Also, conventional wisdom is to have a 1/3 reserve of fuel.

<img src="http://www.indiscipline.org/cat25/pictures/icon.jpg" border=0>Indiscipline 1978 FK #398

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Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 08/19/2003 : 20:02:46

Bob3589,

The only time I took the trouble to do accurate fuel milage calulations, I got about 10 nautical MPG at around 4.5 to 5 knots cruising speed. That was with a Yamaha 4-stroke 10HP high trust outboard running well below full throttle, no significant head or tail wind, currents averaging to zero. For fuel tanks, I carried two 6-gal. Tempo portables plus a 3-gal. portable reserve tank. These took up most of the cockpit sole.

-- Leon Sisson

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Arlyn Stewart
Master Marine Consultant

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USA
2980 Posts

Response Posted - 08/19/2003 : 22:47:00

Dave is right... squeezing the last knot of speed is done at cost to fuel efficiency. My calculations are about 1.6 - 1.7 hours per gal at 5.3 knots. This at about 1/3 throttle. 2/3 throttle will yield hull speed but at greatly increased consumption. More than 2/3 throttle will likely yield a speed loss.

Arlyn C-250 W/B #224
<img src="http://www.stewartfam.net/arlyn/rr.jpg" border=0>
N/E Texas and Great Lakes

[url="http://www.cox-internet.com/arlynstewart/"]Arlyn's C250 Mods n Cruisin Stories[/url]

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Bruce Baker
Captain

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USA
402 Posts

Response Posted - 08/20/2003 : 10:56:22

Here's another data point: I brought my boat up the Potomac from Solomon's Island, MD to Alexandria, VA with an Evinrude 8. The motor doesn't run very well, and coughs if you go over about 3/4 throttle. Anyway, I filled up twice (I carried two 6 gallon tanks) for the 150 mile journey. That's only 6.25 miles a gallon. There was zero wind and (in places) a very stiff current. Your mileage may vary! BTW, I have a new (used) Nissan 8 now.

Bruce Baker
Falls Church, VA
"Yee Ha" 3573
'83SR/SK

Edited by - on

B.Jones
1st Mate

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39 Posts

Response Posted - 08/20/2003 : 13:03:26

Where in Tennessee are you going? I have an '83 TR/FK at Gold Point Marina in Chattanooga (on the TN River) and have been thinking about making the reverse trip down to Mobile.
Bruce
BellaSera #3538

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Bob3589
1st Mate

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31 Posts

Response Posted - 08/20/2003 : 14:10:29

B.Jones -- I'll be going to Pickwick Lake in west Tenn. I'm doing the trip preparation and homework now. This will be my first extended cruise so i am trying to think of all the things i'm going to need and be confronted with along the way. Never been thru a lock before so that should be interesting.

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JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 08/20/2003 : 18:49:42

My crew and I went through 86 locks on our year long voyage. I was very frightened about the first lock. After 85 more we were all quite tired of them! There really is nothing to it.

(1) Motor into the lock and "dock" along the sidewall.
(2) crewperson on the bow either holds the lock line or loop your own dockline around it. Leave it loose and don't mind if your boat moves around a little. Do the same on the stern.
(3) shut down engine, relax, go for a ride. Talk to the lockmaster and the folks on other boats. Read a book. Have a snack. Keep lines loose. It can get messy. Gloves are nice. I had some fenderboards and big fenders over the side to keep the boat off the concrete but it's easy enough to do by hand as well - especially with a C-25.
(4) Start up engine. Let the big guys leave first. Houseboats always get the right of way in my book. Push out bow. Motor away before turning (don't want to swing the stern into the lock).

Locking UP is easier than Locking Down - reason is you are always out of the wind at the bottom of the lock.

Want to see all about locks ? Check this out http://www.indiscipline.org/cruise2000/chapter5/trent.html

<img src="http://www.indiscipline.org/cat25/pictures/icon.jpg" border=0>Indiscipline 1978 FK #398

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deastburn
Captain

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USA
334 Posts

Response Posted - 08/23/2003 : 12:28:03

Because current and wind can cause "gas mileage" to vary widely (as has been pointed out above), it is probabaly more useful for planning purposes to use "gallons per hour" as your measuring yardstick. My Honda 9.9 at 5 nominal knots (about 1/3rd to 1/2 throttle) will burn about a half gallon or less per hour. Before leaving the mooring, I calculate what I am likely to need for the day, factoring in wind and current. If you have to be at point 'B' tonight, and there is no wind (to sail by) and a 1.5 knot tide against you for six hours, then your half gallon of fuel is going to take you only 3.5 nautical miles. Thirty miles will require about 7.4 gallons, given that you'll have the tide with you the last hour and a half (or nine miles). If the tide is with you (and the Force), the same thirty miles will take only about 4.6 gallons (you will arrive at destination before the tide turns). That does not take account of sea conditions, which can further depress mileage, of course.

I carry a 6.5 gallon tank in the fuel locker and another broad-based five gallon can in the rear of the cockpit, lashed to the transom. I always loosen the stopper on the breather a half turn, but I am not sure this is good practice. I know I don't like the idea of gas sloshing around in a plastic can below decks.

Dave on "Wood Duck" (#2616)

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ronrryan
Admiral

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USA
561 Posts

Response Posted - 08/23/2003 : 20:47:18

Once sailed and motorsailed a 26 foot boat around long island NY in a weekend, never mind why. We burned about one half to three quarters gallon per hour at about six knots honest, tides good and bad, seas the same. Since then I estimate two thirds gallon per hour and am not far wrong. When I taught cruising etc for the power squadron a reserve of ten percent minimum, twenty percent usual, on fuel, was customary, I allow more from some nasty experiences already alluded to on other posts, in general it is hard to carry too MUCH fuel on a small boat, good luck and fair winds, ron srsk #2343 Orion 1981 SW FL

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ronrryan
Admiral

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USA
561 Posts

Response Posted - 08/23/2003 : 20:47:26

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