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 Tohatsu 9.8 hp fuel consumption		  New Topic  Topic Locked
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willyd103
1st Mate

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USA
49 Posts
Initially Posted - 07/09/2012 :  15:46:21  Show Profile
Folks,
Got my new 9.8 Tohatsu a month ago and have done the 10 hour break in cycle. Wondering if anyone has some fuel consumption info for this outboard? Gallons per hour for a specific RPM? Just doing some cruise plannign and want to know if I should plan on an extra 3.5 gallon tank in the port locker.
Best regards,
S/V Stardust
1996 WK C-250 #215
Willyd103
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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts
Response Posted - 07/09/2012 :  16:25:46  Show Profile  Visit delliottg's Homepage
Will,
I don't have hard numbers for you, but I can give you my impressions on our Tohatsu 9.8. [url="http://www.tohatsu.com/tech_info/fuel_consumpt.html"]Tohatsu lists the burn rate for your OB at 1 gallon per hour at 5500 RPM[/url]. I don't think I've ever had mine up to that RPM, maybe 2500 max. If I were going to guess a burn rate for ours, it'd be somewhere around a half a gallon an hour, maybe a little less, at about 1400 RPM. That's enough to push our WK at about 4.5-5 knots comfortably. When we go cruising, we take our 6 gallon can, plus the 3 gallon can that came with the Tohatsu for a total of just shy of 10 gallons of fuel. You should plan to use 1/3 to get where you're going, 1/3 to get back, and 1/3 in reserve.

Once I refill the tank, I'll have a better idea of our current burn rate, I know about how far I've traveled on the engine, and how fast we were going.

If you want to be conservative, use Tohatsu's published consumption rate when doing your planning. I'd be willing to bet they've fudged the data toward conservative already.
Edited by - delliottg on 07/09/2012 16:26:16
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Jack Schafer
Navigator

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USA
112 Posts
Response Posted - 07/10/2012 :  08:40:53  Show Profile
I have no hard facts either, but I am pleased with the the consumption rate of the Tohatsu. My old Johnson 9.9 used about 1.5 gal/hr. and the last few years probably more. I have to motor about 40 min.each way to race on Wed nights and had been burning at least 2 gals. I have had the Tohatsu since June 1 and have only burned 5 gals. I also never have to run more than 1/3 throttle to get to 4-5 kns. any more than that is wasted. so far it has been good.
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Sloop Smitten
Master Marine Consultant

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USA
1181 Posts
Response Posted - 07/10/2012 :  09:35:30  Show Profile
Last year I motored 66 miles (57 nautical miles) in my fully loaded "C25" and burned 6 gallons at 5 - 5.5 knots (about 1/3 throttle) with my Tohatsu 9.8. It took about 12 hours so I used about .50 gallons an hour. The last 3 hours were into a pretty good head wind and seas. I had just tuned up the engine with new plugs and oils. Making the same trip in a couple of weeks and can let you know how that turns out.
Edited by - Sloop Smitten on 07/10/2012 09:48:30
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TakeFive
Master Marine Consultant

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2272 Posts
Response Posted - 07/10/2012 :  09:37:49  Show Profile
The old rule of thumb that I was always taught was 1 gal/hour for every 10 horsepower at full throttle. This was in the days of 2 cycle engines, and my 50 hp motor on my Trophy boat fit that rule pretty well. I'd expect modern 4 cycle motors to do a little better, but not by a huge amount. And be sure to account for the fact that a sailboat at hull speed is usually well under full throttle.
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piseas
Former Treasurer

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USA
2017 Posts
Response Posted - 07/10/2012 :  10:27:12  Show Profile  Visit piseas's Homepage
Will, How many miles are you planning on? Be conservative re consumption. I have a 6 gallon tank in the fuel locker for those long trips but still keep the 3 gallon full on board as backup. Make sure you have quick disconnects for all tanks as you dont want to be pouring in any type seas, especially rough.
Steve A
Edited by - piseas on 07/10/2012 10:27:59
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willyd103
1st Mate

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USA
49 Posts
Response Posted - 07/13/2012 :  13:37:27  Show Profile
Thanks everyone for the info. I'll have 9 gallons on board for the one way 20 nautical mile cruise and plan to re-fuel when I arrive in Scituate, MA. More info coming next week.
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willyd103
1st Mate

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USA
49 Posts
Response Posted - 07/20/2012 :  04:40:22  Show Profile
The 20 nautical mile trip took four hours of motoring. Average speed was 5 knots and the Tohatsu 9.8 used 1.8 gallons. No RPM info as I don't have a tachometer.
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TakeFive
Master Marine Consultant

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2272 Posts
Response Posted - 07/20/2012 :  05:19:15  Show Profile
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by willyd103</i>
<br />The 20 nautical mile trip took four hours of motoring. Average speed was 5 knots and the Tohatsu 9.8 used 1.8 gallons. No RPM info as I don't have a tachometer.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
Sounds like you had a little extra gas!

You used about half a gallon per hour. Our boats hit hull speed at about 1/2 throttle on a 10 hp motor (motor putting out ~5 horsepower). That fits my rule of thumb of 1 gal/hour for every 10 horsepower.
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DaveR
Master Marine Consultant

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USA
2015 Posts
Response Posted - 07/21/2012 :  06:44:11  Show Profile  Visit DaveR's Homepage
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"> That fits my rule of thumb of 1 gal/hour for every 10 horsepower.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

I never knew or had a formula for gas mileage, good to know!
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