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Water Dawg 6

Fuel/Power Opinion

14 posts in this topic

I have Sig 290 with twin Mercruiser 5.0 MPIs with Bravo III outdrives each pushing 260 hp.  Currently, it take me over an hour and half to get out to the ocean from my Marina.  By the time I get there I've already went through a significant amount of fuel. Someone suggested that I only run engine to get out there (note:  I travel down a creek that is always flat as a pancake).  I've never ran the boat with one engine.  Just wondering if it would want to pull to one side, would I be straining the engine and is this a good idea to try to save fuel?  Currently, with both engines I usually cruise around 28 knots or so down the creek.  Not seeing that happening running only one engine. 

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So it's roughly 42 knots from your marina to the ocean.  Let's say with one engine you can do 6 knots.  It'd take you 7 hours to get to the ocean.   No way you're planing in that boat with one engine. 

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one is fine to use but its going to work twice as hard now on plane.  Not sure the numbers would be in your favor.  so its roughly 15 miles or so to get out to where you want to go?  If that's the case then your talking about using probably 7-10 gallons to get out there.

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You would not be able to do 28 knots on one engine. You also have the drag of the extra outdrive. Stick with running both engines. 

brick

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Is it worth calculating time saved. Fuel saved if your boat was at the inlet marinas ? 

IF IF car speed is always faster?

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First off, YES the boat is not going to go straight.  

What speed and RPMs are you doing in that 1 and half hour? How mush fuel are you using? Also, your boat will never get on plane with one engine.

I would install a fuel flow sensor or tap into the engines computer if it has one, to really see your GPH rate. 

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Thanks all.  Cyclops, I'm in the NC Outter Banks and the Marina's close to the inlet want heard of deer to dock there.  Definitely wouldn't be more cost effective and my truck wouldn't pull this boat even if I had a trailer so that option is out the window as well.  It's about 25 miles to the start of the fishing grounds but my fuel consumption is just terrible that is why I was pondering running on one engine.  My initial thoughts were right in line with Brick and Soldier just wanted to tap you guys for your opinions on this.  Iggy, I have Garmin Fuel Flow sensors installed and what they tell me is my boat drinks more fuel than I do beer lol.  I usually run about 3,600 RPMs heading down the creek towards the inlet, going about 26-28 knots.  I usually back off of it on my way back to the dock so that I know I will make it back to the dock - slowing to 3,000 RPMs. 

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5 minutes ago, Water Dawg 6 said:

Thanks all.  Cyclops, I'm in the NC Outter Banks and the Marina's close to the inlet want heard of deer to dock there.  Definitely wouldn't be more cost effective and my truck wouldn't pull this boat even if I had a trailer so that option is out the window as well.  It's about 25 miles to the start of the fishing grounds but my fuel consumption is just terrible that is why I was pondering running on one engine.  My initial thoughts were right in line with Brick and Soldier just wanted to tap you guys for your opinions on this.  Iggy, I have Garmin Fuel Flow sensors installed and what they tell me is my boat drinks more fuel than I do beer lol.  I usually run about 3,600 RPMs heading down the creek towards the inlet, going about 26-28 knots.  I usually back off of it on my way back to the dock so that I know I will make it back to the dock - slowing to 3,000 RPMs. 

your going to get 2 mpg roughly and burn 12-15 gallons going 25miles just the way it is.  Like I said running one might work for idle and slow speeds and see how it goes, but doubtful of any improvement.  In order to improve efficiency you could look at ensuring your flame arrestor is clean, new spark plugs and cap and rotor.  Maybe even try a few cans of sea foam or marvel mystery oil, not a huge buyer or believer but those things have worked magic in the past for others and myself.  Lastly maybe experimenting with fuel, most boat engines run the best on 87 ironically enough and buying premium is just money out the window.  maybe trying different grades will have an affect.  Also check to make sure you bottom is clean.

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As already said, the 2 MPG is what you need to assume, at best 2.5 MPG if you trim the drive and tabs and find that sweet spot and most efficient RPMs ... most likely 3600 RPM is close to it. Running on one engine only is a loosing proposition from the get go for many reasons.

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So if we assume a typical  2.5 mpg, then you will burn around 20 gallons getting to and from your marina. Let's call it $100 in gas. How many times a year do you do this? How much extra is it to get a slip st a closer marina? Compare that cost increase to your higher annual fuel cost.

brick

 

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I'm not familiar with the Signature series but on my 224 with 5.0Gxi, I would not consider 3600 RPM to be cruise speed - the boat settles into a nice cruise at around 3000 RPM and on my boat I would not "cruise" at 3600 unless I was trying to get back due a deadline or storm.  I'm sure your boat is different due to size and dual engines, but off the cuff it seems that you could back off a bit, assuming you can stay on plane and so forth.  My two cents anyway...

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7 minutes ago, jhole said:

I'm not familiar with the Signature series but on my 224 with 5.0Gxi, I would not consider 3600 RPM to be cruise speed - the boat settles into a nice cruise at around 3000 RPM and on my boat I would not "cruise" at 3600 unless I was trying to get back due a deadline or storm.  I'm sure your boat is different due to size and dual engines, but off the cuff it seems that you could back off a bit, assuming you can stay on plane and so forth.  My two cents anyway...

every boat is different, but I would agree 3600 seems high for cruise speed.  experimenting with different rpm might net you a savings.  5 extra mins one way might save you a few bucks.  But yeah if its a $100 bucks to just get out and back maybe relocating is an idea if you do it a lot.

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6 hours ago, Water Dawg 6 said:

Thanks all.  Cyclops, I'm in the NC Outter Banks and the Marina's close to the inlet want heard of deer to dock there.  Definitely wouldn't be more cost effective and my truck wouldn't pull this boat even if I had a trailer so that option is out the window as well.  It's about 25 miles to the start of the fishing grounds but my fuel consumption is just terrible that is why I was pondering running on one engine.  My initial thoughts were right in line with Brick and Soldier just wanted to tap you guys for your opinions on this.  Iggy, I have Garmin Fuel Flow sensors installed and what they tell me is my boat drinks more fuel than I do beer lol.  I usually run about 3,600 RPMs heading down the creek towards the inlet, going about 26-28 knots.  I usually back off of it on my way back to the dock so that I know I will make it back to the dock - slowing to 3,000 RPMs. 

As Richard mentioned, trim her out and note the fuel flow meter. Keep adjusting the trim and throttle until you get the best GPH rate. I too have a 290, but I have 4.3L engines and at 3200-3300 RPMs I can do about 26 to 28 knots. Sucking down 18-19GPH. If I go faster or slower, I just suck down more fuel. Meaning that my MPG go down.

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Do you know which engine controls the power steering?

You are not getting on plane with one engine.

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