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Wildcat Dude
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| Posted: 07/06/2008 at 2:49pm | IP Logged
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Hello! I have a 20 ft. 1997 90 hp Johnson 2-stroke outboard motor that runs well, but seems to be guzzling gas.....I think ??? I don't know anyone else with a pontoon boat to compare gas usage. I can drive for approximately 1.5-2 hours on 10 gallons of fuel (not towing) and not at full throttle. Does this sound reasonable? I don't have a mph gauge to show mph or rpms, but I am careful not to go at full speed, etc.
I've thought about buying new, but hate to spend that kind of money to just save 5-10% on fuel costs.
Any advice or data to compare my fuel usage to would be appreciated ! |
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Holly Cow Batman!!! I hope that isn't right because I intend on getting a 90 before too much longer. My 40hp will go many many hours (I know its no comparion to a 90 but still) on 18 gal (actually several trips of several hours). I generally only go about 3000 rpm (WOT is 53-5400 for me). Surely some of these guys have 90's on a 20 or 24ft which would give you some kind of comparison. Are you sure you don't have a leak somewhere like around the motor where it might be just going in the drink? (shuddering at the thought of all that gas being wasted  )
Edited by Wildcat Dude on 05/18/2009 at 7:52am
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Charles - TN
93 Voyager 20ft
84 Johnson 115HP
68-77 USAF SP-K9 Vietnam 69 & 70
Retired Detective 94
www.ezacdc.com (for wiring)
www.backtoboating.com (good stuff)
www.boatingseats.com (seats)
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Wildcat Dude
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| Posted: 07/06/2008 at 2:54pm | IP Logged
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I was just thinking, where is your tank currently? And what type are they? Permanent or Portable? Have you checked to make sure its not leaking underneath it from a stress fracture. If its a permanent tank, do you have a fuel gauge on it? When it shows empty, is it truly empty (could be faulty sensor) Just trying to ask all the questions as to get an idea what it could be (since the motor seems to be running fine and not flooding or anything else amiss)
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Charles - TN
93 Voyager 20ft
84 Johnson 115HP
68-77 USAF SP-K9 Vietnam 69 & 70
Retired Detective 94
www.ezacdc.com (for wiring)
www.backtoboating.com (good stuff)
www.boatingseats.com (seats)
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rickdb1
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| Posted: 07/06/2008 at 3:19pm | IP Logged
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Here's some reading from my 07' 90 HP 4 stroke.
Edited by rickdb1 on 02/14/2009 at 8:50pm
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Rick
2007 Bentley 200 Cruise
Merc. 90 HP 4 stroke
Mo.
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Wildcat Dude
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| Posted: 07/06/2008 at 4:22pm | IP Logged
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So yep, based on that, if you're going 5000 rpm you'd go through 10gal in 1.5-2hrs, at full throttle you'd use up that gas in an hour (ouch)
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Charles - TN
93 Voyager 20ft
84 Johnson 115HP
68-77 USAF SP-K9 Vietnam 69 & 70
Retired Detective 94
www.ezacdc.com (for wiring)
www.backtoboating.com (good stuff)
www.boatingseats.com (seats)
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rickdb1
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| Posted: 07/06/2008 at 4:31pm | IP Logged
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I usually cruise at 4000 or so and that gets me around 18-19 MPH on my 20' 2 logger. Nice speed for running around and much better milage than wide open..
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Rick
2007 Bentley 200 Cruise
Merc. 90 HP 4 stroke
Mo.
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rickdb1
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| Posted: 07/06/2008 at 8:23pm | IP Logged
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Evinrude has the I-Command line of gauges that are pretty much like the Merc. Smartcraft gauges. Some info below..
http://continuouswave.com/whaler/reference/BRP/I-CommandSupp lementRev.pdf
http://continuouswave.com/whaler/reference/BRP/353571_IComma ndInstallationGuide.pdf
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Rick
2007 Bentley 200 Cruise
Merc. 90 HP 4 stroke
Mo.
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rickdb1
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| Posted: 07/07/2008 at 4:22pm | IP Logged
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The thing that amazed me the most was from 5000 to 5900 RPMs. Almost 4 gallons per hour savings by throttling back just 900 RPM's...
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Rick
2007 Bentley 200 Cruise
Merc. 90 HP 4 stroke
Mo.
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Frankenstien
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| Posted: 08/10/2008 at 10:32pm | IP Logged
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My results nearly mirror ricks with the 115 Merc. 4 stroke.... seldom do I ever run at WOT for more than 20-30 min.... 95% of my cruising is around the 25-3K range... fuel will last me all day and then some.
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20' Fischer 115 Mercury WaterGlide Center...
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cuzzx
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| Posted: 01/04/2009 at 8:35pm | IP Logged
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check the prop, check that you have the best prop for the job and also check where motor is sitting on transom, i had to move mine up 2 holes to better my milage.
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cuzzx
2000 Dodge D
18'Bandit Toon 1993(???)
75hp Evinrude
20'Stardust/Landau Toon 1995
75hp Mariner
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flybob
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| Posted: 03/23/2009 at 7:06pm | IP Logged
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Nice info but I wish you had included what speed your instruments were showing!!
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Wildcat Dude
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| Posted: 03/23/2009 at 8:28pm | IP Logged
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Speed is irrevelant though as everyone will be different, but the rpm and gal per hr is revelant to all boats don't you think since the topic is poor gas mileage  or was you just curious how fast Rick can go based on his RPM's on his boat.
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Charles - TN
93 Voyager 20ft
84 Johnson 115HP
68-77 USAF SP-K9 Vietnam 69 & 70
Retired Detective 94
www.ezacdc.com (for wiring)
www.backtoboating.com (good stuff)
www.boatingseats.com (seats)
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VaGent
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| Posted: 03/30/2009 at 8:17pm | IP Logged
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If I remember correctly Charles you had a Johson 70 2-stroke on your toon originally did you not? What kind of gas milage did you get with it & at what RPMs? I'll be putting my Johnson 70 on the 24 footer I just got & was just curious. Maybe a 'ballpark' guesstimation? I'll be using a 18 gallon tank. I have not run the Johnson 70 other then to test it out & it runs & idles great. Nice throttle response when we tested it. WE did not have a tach to see what RPMs we were running but I will have one on the boat when I am finished with the remodel.
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Les
"Atta Boy Award July 2010"
1984 24ft JC
1987 Johnson 70hp VRO w/T&T
Virginia
Boating, fishing & camping
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Wildcat Dude
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| Posted: 03/30/2009 at 11:17pm | IP Logged
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I had a 40hp, I could go for days on my 12 gal tank as I rarely went above 3000 rpm as it was my best cruising speed. Didn't see the need to run it WOT to gain 3-5mph. Time will tell what the 115 does and now that I've got a GPS I'll know for sure. Would love to get one of those gauges Rick has.
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Charles - TN
93 Voyager 20ft
84 Johnson 115HP
68-77 USAF SP-K9 Vietnam 69 & 70
Retired Detective 94
www.ezacdc.com (for wiring)
www.backtoboating.com (good stuff)
www.boatingseats.com (seats)
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rancherlee
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| Posted: 04/17/2009 at 9:06am | IP Logged
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4 strokes really save you in the mid range for gas usage. I went from a carbed 70hp 2 stroke to an EFI 70hp 4 stroke on a fishing boat (the 4 stroke is now on my pontoon) and in the 3500rpm range the 4 stroke got 50%+ better fuel economy using only 2.5gph compared to 4gph. WOT is closer though. I burn 6gph 4 stroke, 7gph 2 stroke. The lower the RPMs the more fuel I save with the 4 stroke though. I can Idle/troll @ 650 rpm for ~3 hours on a gallon of gas, the 2 stroke burn more than 1 GPH at idle/troll so a 300% difference there.
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87' Kennedy 20 foot
98' Johnson 70hp 4 Stroke 14x13 OMC prop.
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craig4080
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| Posted: 06/24/2010 at 10:48am | IP Logged
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I saw an interesting stat in Boating Magazine... at wide open throttle, a boat consumes 7.8 gallons per hour per 100HP.
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1998 Smokercraft Sunsport 24ft
1987 Evinrude 110 V4
Lake Allatoona, Georgia
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cuzzx
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| Posted: 06/24/2010 at 8:08pm | IP Logged
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That sounds about right.
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cuzzx
2000 Dodge D
18'Bandit Toon 1993(???)
75hp Evinrude
20'Stardust/Landau Toon 1995
75hp Mariner
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PontoonStuff Forum : Tips, Tricks, and things to know
Topic: poor gas mileage on 90hp Johnson
