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Old 05 June 2008, 11:00   #1
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Fuel usage help

Hi,

please could you help..... i have a 1990 or a 1998(im not sure) 40hp Mariner electric start and trim engine. The fuel usage is completely apauling like £28 in 5hrs of going 4 knots!!! THIS CANT BE RIGHT!!! Please can someone advise on what they think about sorting it out so its more economic!!

Thanks,

Alex
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Old 05 June 2008, 11:22   #2
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I work that out to be 1.25Lt per mile so not that bad, how big is the boat?
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Old 05 June 2008, 12:22   #3
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Quote:
Originally Posted by ali_seton View Post
Hi,

please could you help..... i have a 1990 or a 1998(im not sure) 40hp Mariner electric start and trim engine. The fuel usage is completely apauling like £28 in 5hrs of going 4 knots!!! THIS CANT BE RIGHT!!! Please can someone advise on what they think about sorting it out so its more economic!!

Thanks,

Alex
Sounds about right to me. You should not assume that going slow is more economical. It is not as you are just pushing water. A planing hull is at it's most efficient on the plane at about 3500-4000 RPM.
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Old 05 June 2008, 13:50   #4
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Yep. sounds about right to me too.
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Old 05 June 2008, 14:19   #5
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it cant be right as when i am going at speed the boat does about £10 per 30 minutes! its a 4m rib
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Old 05 June 2008, 14:47   #6
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it cant be right as when i am going at speed the boat does about £10 per 30 minutes! its a 4m rib
Yes, but you travel X times the distance. Fuel consumption is primarily distance related not time. Get your calculator out.
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Old 05 June 2008, 15:31   #7
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ok..... is there anything i can do to lower fuel usage????
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Old 05 June 2008, 15:36   #8
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ok..... is there anything i can do to lower fuel usage????
Buy some oars
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Old 05 June 2008, 16:05   #9
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My RIB does about 5mpg on tickover which is about 5mph. That is near enough 1L per mile - not so bad for a 225hp so maybe his is a little thirsty - my boat isn't exactly small either!!!
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Old 05 June 2008, 16:21   #10
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no im being serious is there anything i can do to make it more fuel efficient..... my mates gt a 5.2 avon searider with a 70 autolube yamaha and it uses like half the fuel mine does!! please is there anything i can do???????
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Old 05 June 2008, 16:47   #11
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it could be running seriously rich - does it have a sticking autochoke or anything?
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Old 05 June 2008, 18:06   #12
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hi thanks...... what is a sticking autochoke?
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Old 05 June 2008, 18:10   #13
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£28 for 5 hours running...

Approx 20lts, so 4lts an hour
Sounds pretty normal to me.
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Old 05 June 2008, 18:16   #14
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hi thanks...... what is a sticking autochoke?
does it have a manual choke or an automatic one?
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Old 05 June 2008, 18:18   #15
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Hi,

please could you help..... i have a 1990 or a 1998(im not sure) 40hp Mariner electric start and trim engine. The fuel usage is completely apauling like £28 in 5hrs of going 4 knots!!! THIS CANT BE RIGHT!!! Please can someone advise on what they think about sorting it out so its more economic!!

Thanks,

Alex
If it's a very used engine, make a compression test if OK, are you using the correct gapped spark plug type ? If worned or too fouled, change for new ones, if OK, would think in changing complete carb accesories for new ones, with time and use high speed orifice and jets tend to wider their gas hole passages comsumming more gasoline as before. Check also for any gas leaks in gas filter, pump, hoses, etc. Don't know if your engine is a Tohatsu or Yamaha manufacture rebadged to Mariner brand, Tohatsu manufacture uses rack & piñon throttle arm photo 1, Yamaha uses cable drive throttle arm photo 2.

If it were a Tohatsu the factory consumtion parameters are:

Full Throttle Engine RPM Range : 5200-5800 rpm
Full Throttle Engine Comsumtion (WOT) 4.49 Gal/Hour (17 Ltr/Hour) 3.78 Ltr to Gallon

Does not state if tested on a factory test tank, or on a boat with calm waters.

Happy Boating
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Old 06 June 2008, 13:59   #16
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thanks... the choke is on the controls..... you push the key in to choke
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Old 06 June 2008, 16:25   #17
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it could be the choke is sticking or just the carb needs adjusting.
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Old 07 June 2008, 03:16   #18
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thanks.... how can i check and adjust those?????
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Old 07 June 2008, 03:22   #19
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Get the engine serviced. Not only will it be tested for the optimum fuel efficiency, but they will check other items like water pressure, change the gearbox oil etc to provide you with a safer and a longer term cheaper boating experience.

I don't think that you'll ever acheive the sort of economy that you're looking for, welcome to the world of digging holes and throwing money away
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Old 07 June 2008, 11:52   #20
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Get the engine serviced. Not only will it be tested for the optimum fuel efficiency, but they will check other items like water pressure, change the gearbox oil etc to provide you with a safer and a longer term cheaper boating experience.

I don't think that you'll ever acheive the sort of economy that you're looking for, welcome to the world of digging holes and throwing money away
Hightower is right, get the engine serviced by a qualified reputed shop for best engine performance, or opt for a less HP engine 25/30. Outboards are fuel eaters compared to motorcycles and cars for the same travelled distance. Part of the divertimento is to spend huge amounts of money, a lot worse with fuel prices now a days, definitely not a cheapy sport, but fun anyway.

Happy Boating
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