How can I get better gas mileage with my boat.

J

johnjm1234

New Member
Jun 18, 2009
23
waverly, iowa
Boat Info
working on a 1985 26 foot sea ray sundance it need a lot of work but I will keep plugging away at it
Engines
260 mercruiser
My boat uses alot of gas how can I enprove the mileage on it. The boat is 1985 Sea Ray with a 260 merc Courser engine which is really a 350 chev engine. It has a four barrel carberator on it. I did find out once I get up on plane if I run it 3200 rpm that it will run on the two barrell but if I put up 4200 rpm it kikc the four barrel in then I only get about a mile per gallen of gas. IT is bad need help something is not wright. Help
 
That sounds about right really.

When cruising, I'm about 70l/hour for 20-22kts. That chops to 1gal/nm.

You're a little smaller, so when you open right up, I'd personally expect to to hit about the same numbers as me.

I'm a bit of a newbie tho, so I'll be following any responses you get with interest.

Assuming you've got bottom paint, properly prop'ed?
 
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I had a 28 footer non Searay with twin 3.8 V6ies stern drives it had upper and lower helm. It was a heavy boat. Fuel consumption at 22 knots was 1 liter a minute that is 16US GPH. Based on that and the engines you have I would say you are burning what you should. Slowing down did not improve fuel consumption. Present boat burns 1 US gallons per knot cruising at 6 knots.
 
johnjm1234 said:
My boat uses alot of gas how can I enprove the mileage on it. The boat is 1985 Sea Ray with a 260 merc Courser engine which is really a 350 chev engine. It has a four barrel carberator on it. I did find out once I get up on plane if I run it 3200 rpm that it will run on the two barrell but if I put up 4200 rpm it kikc the four barrel in then I only get about a mile per gallen of gas. IT is bad need help something is not wright. Help
Click to expand...

Only way to significantly improve your mileage is to switch to diesel.
 
I have a Mercuriser 5.7L (350 ci) with a 4 BBL carburetor and I get 2.1 MPG at 3800 RPM. I use a Garmin GFS-10 connected to a Garmin 740S to measure that.
 
The only other thing that might improve is well tuned up engines, clean bottom and tuned props.
 
What pitch is your prop? My 1987 Monaco with the same engine AT the same RPM would vary the mileage based on whether or not I had the 17 pitch or the 19 pitch prop... The 17 got me on plane quicker while the 19 cruised better and ran the same speed at a lower RPM.


johnjm1234 said:
My boat uses alot of gas how can I enprove the mileage on it. The boat is 1985 Sea Ray with a 260 merc Courser engine which is really a 350 chev engine. It has a four barrel carberator on it. I did find out once I get up on plane if I run it 3200 rpm that it will run on the two barrell but if I put up 4200 rpm it kikc the four barrel in then I only get about a mile per gallen of gas. IT is bad need help something is not wright. Help
Click to expand...
 
When I had a boat it got about 0.68mpg at cruise on a good day with a tail wind. Consider yourself lucky and welcome to boating!
 
johnjm1234 said:
My boat uses alot of gas how can I enprove the mileage on it. The boat is 1985 Sea Ray with a 260 merc Courser engine which is really a 350 chev engine. It has a four barrel carberator on it. I did find out once I get up on plane if I run it 3200 rpm that it will run on the two barrell but if I put up 4200 rpm it kikc the four barrel in then I only get about a mile per gallen of gas. IT is bad need help something is not wright. Help
Click to expand...


as you can tell from the various 'helpful' replies you have received the words 'boating' and 'fuel economy' do not go together....you can minimize the amount of money spent on fuel by altering the way you use the boat to involve a lot of time 'on the hook' and/or slow speed cruising....we normally cruise for around 30 mins to an hour when we go out then find a nice secluded cove somewhere and drop anchor...then we swim or float behind the boat for the remainder of the day and cruise back to the dock if we are not going to camp that night....this way the fuel usage and cost is minimized while we still enjoy being out on the boat....

cliff
 
I have a 300DB with twins and get about .8MPG on step at 3200. I have found that going slower, 10 mph or so you get a lot better MPG. Praticing being a trawler.....So slower=more MPG!
 
Bit of a left field one, have a friend with a 26ft bayliner who was using 100l +/hour just cruising.

Turned out to be a bad fuel pump that was massively over pressurizing the fuel flow.
 
I get about .8 mpg at 3200 with 2 of the same engines. Count your blessings if you're getting 1+ mpg.
 
Heck, he's getting 1mpg at WOT! That's still pretty impressive.
 
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