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Old 29 June 2013, 19:00   #1
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merc 50 elpto fuel consumption

I've gone turn coat and bought a small sports cruiser with a 2002 merc 50 2 stroke and I'm a bit horrified about the fuel consumption.

Took it on It's first trip today and used about 20 litres in 4 hours going 6 knts (was inland) with a few mins at wot doing about 26 knts to see what speed it could do.

I was expecting it to be worse than my SIB but not by that kind of margin. The boat weighs around 700kg. Is that rate of fuel use to be expected or is it excessive to the point that there is something wrong with the engine?

It seems to me that if it uses fuel at that rate at low speeds I'd be lucky to get more than a couple of hours from a 25 litre tank cruising on the plane. Or is using a planing hull at displacement speed part of the problem? The 6 knt speed limit requires about 3k rpm. If I power it up on to the plane it will stay on it to around 4k rpm.

Can't work out if I dramatically underestimated fuel consumption or if the engine has a problem.

Thanks

Matt
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Old 29 June 2013, 19:28   #2
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Hate to say it, but a couple of hours cruising from a 25 litre tank would be a luxury on most boats above 40hp. Like it or lump it I'm afraid-it won't get much better.
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Old 29 June 2013, 19:37   #3
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Hate to say it, but a couple of hours cruising from a 25 litre tank would be a luxury on most boats above 40hp. Like it or lump it I'm afraid-it won't get much better.
Thanks for the reply Nos. I thought it was going to turn out it was normal. Putting my grandmother up for sale on eBay as we speak!
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Old 30 June 2013, 01:07   #4
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Thanks for the reply Nos. I thought it was going to turn out it was normal. Putting my grandmother up for sale on eBay as we speak!
Rule of thumb..... With wot, its a gallon an hour per 10hp, so a 50hp would roughly burn 5 gallon an hour at wot,give or take a bit....hope this helps
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Old 30 June 2013, 02:52   #5
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A mid 90's 50 elpto used 22 L/H at WOT and 14.8 L/H at -1000 RPM according to an old boat test i have.

According to my fuel flow meter, my Searider uses more fuel /mile at displacement speed than at WOT (or any other speed i use), speed limits is a real killer for old 2 stroke engines...
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Old 30 June 2013, 04:04   #6
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I afraid your consumption looks about right but there may be a glimmer of hope.

What boat have you got ? 6kts can be a really inefficient speed in a hard boat, you are probably starting to push hull speed and you are using a lot of power to push water and only go a little faster.

Try dropping back to 5mph its probably only 1000revs, your journeys wont take much longer and you will save fuel.
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Old 30 June 2013, 04:27   #7
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This might make you feel better....my rib burns through 90 litres an hour at cruising speed, going up to 140 litres an hour at WOT
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Old 30 June 2013, 06:10   #8
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Thanks for all the feedback.

The boat is a Galeon galia 485. Good to know there is nothing wrong the engine, I'll try going a bit slower and see if that helps. Looking as some of the figures on this thread it looks like I'm getting off lightly though!
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Old 30 June 2013, 06:20   #9
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This might make you feel better....my rib burns through 90 litres an hour at cruising speed, going up to 140 litres an hour at WOT
Nice to know my Opti' is about right at 8-10 US GPH at cruising speed then
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Old 30 June 2013, 06:34   #10
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Personally I've redefined the cost of fuel from mpg to fpg, fun per gallon, I've not altered the gauges yet! but when you wiegh up the cost of other simular ways of adrenalin pumped fun, fpg can work out quite cheep.
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Old 30 June 2013, 09:45   #11
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Nice to know my Opti' is about right at 8-10 US GPH at cruising speed then
Wow..You've put me off getting a big rib.my 70ft tug doesn't use that much fuel when its working hard..I'll stick with my sib..
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Old 30 June 2013, 11:17   #12
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Wow..You've put me off getting a big rib.my 70ft tug doesn't use that much fuel when its working hard..I'll stick with my sib..
Nah, but it doesn't do 35 miles in that hour either.
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Old 30 June 2013, 11:23   #13
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Nah, but it doesn't do 35 miles in that hour either.
It'll drag 70 tons at 5mph though..lol..
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Old 30 June 2013, 15:44   #14
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I have a late 80s 60hp Merc 2S and on my Tornado 5mtr, which is very light it uses about 1,2ltr/mile at its absolute most economical ie crusing on a flat sea at 16kts.

Mine uses loads mucking about at low speeds, I am afraid these things are NOT economical but they are simple, easy to fix, cheap to service etc and in my experience reliable.

As others have said that consumption sounds about right.

Davej
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Old 30 June 2013, 16:22   #15
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yeah and there I was putting rocknroll on that 9 mtr with the 2 x 200 behind in the Mania you should have seen fuel consumption then thought it was the rev counter , only because his boat got a on \ off switch
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Old 30 June 2013, 16:23   #16
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VAC2 was using 29 litres a mile on their trip back from Spain!
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Old 02 July 2013, 13:41   #17
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You need to optimize prop to achieve near max rpm factory stated parameters for that engine while moving a light, medium, loaded boat.

4K at wot is very low rpm, engine should run at least 5.5 K or will be stressed considerably, could end ruining it too. It's like going up hill with your car heavily loaded on third gear. Check which Honda props are availabe to rise rpm to near it's top stated rpm when at wot. Your fuel consumption will definitely better.

Get factory min-max wot rpm parameters for that engine and go from there playing with less pitch.

Happy Boating
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