Gas mileage for 260 Sundancer

[Flytrade]

My 260 Sundancer has the 350 Mag engine with Bravo 3 drive. According to the boat test reports they were getting 2.6 miles per gallon from 3,500 to 4,000 rpm.

My best cruise seems to be at about 3,800 rpm, producing a speed of about 23 mph, which gives me about 2 miles per gallon. My mechanic says that is about right, but I'm wondering if any of you, with a similar boat, are getting the posted 2.6 miles per gallon, or something close. Your thoughts would be appreciated.

 

[b_arrington]

2.6 mpg seems possible only under absolute ideal conditions with bare minimum weight. It seems improbable in the real world.

I get 1.5 to 1.8 mpg at cruise.

Btw, 23 mph at 3800 rpm seems a bit slow. I usually get few more mph at that rpm.

 

[bbwhitejr]

We had the same set up-2006 260DA w/ 350Mag and Bravo 3 OD. Full water, full gas, my wife and I set up for the weekend and cruise was 3700-3800rpms burning 13.0 gph and doing 27mph measured by GPS=2.08mpg. We had the extra weight of a generator and a 3rd battery.

WOT was 5050rpms and 41mph.

Your 23mph is slow at the stated rpms. Do you have the OD trimmed out?

Bennett

 

[Flytrade]

Thanks for your replies. I'll have to check my rpm's vs speed more closely on calm water. This last trip, where I used just over 50 gallons, was going into white caps in the gulf. I'm sure that could have taken a toll on my gas mileage.

 

[b_arrington]

We had the same set up-2006 260DA w/ 350Mag and Bravo 3 OD. Full water, full gas, my wife and I set up for the weekend and cruise was 3700-3800rpms burning 13.0 gph and doing 27mph measured by GPS=2.08mpg. We had the extra weight of a generator and a 3rd battery.

WOT was 5050rpms and 41mph.

Your 23mph is slow at the stated rpms. Do you have the OD trimmed out?

Bennett

I'm really surprised at those numbers, especially the top end!

I have a 270AJ (same hull form) with the same motor but no generator and 2 batts. For comparison with a light load just after spring splash my best speed ever (since new) at WOT was 32 mph at 4800 rpm. Cruising at 27 mph with a moderate load generally gets me 3800-3900 rpm and about 15-16 gph. That's in calm seas with the drive trimmed out and the tabs up.

Have you ever changed your props? Just wondering how you got your top end with the setup I have.

 

[Lazy Daze]

I'm really surprised at those numbers, especially the top end!

I have a 270AJ (same hull form) with the same motor but no generator and 2 batts. For comparison with a light load just after spring splash my best speed ever (since new) at WOT was 32 mph at 4800 rpm. Cruising at 27 mph with a moderate load generally gets me 3800-3900 rpm and about 15-16 gph. That's in calm seas with the drive trimmed out and the tabs up.

Have you ever changed your props? Just wondering how you got your top end with the setup I have.

Something is wrong there. That is WAY low. If you're using the trim properly, then you should have no problems getting quite a bit higher. You're RPM's are good, though... are you sure your speedo is accurate (or pitot not clogged)? Verify with GPS?

 

[b_arrington]

Something is wrong there. That is WAY low. If you're using the trim properly, then you should have no problems getting quite a bit higher. You're RPM's are good, though... are you sure your speedo is accurate (or pitot not clogged)? Verify with GPS?

Yes, always verified with gps and also with a paddlewheel. My pitot gave up long ago so I've never relied on it. In the spring I always want to benchmark my top speed for the season with a clean bottom and light load. I take 2 passes 1 each direction to account for currents. IIRC, the fastest I ever got was 32 mph; I might have touched 33 with a very light load.

Since I usually take a couple longer trips per year I've spent a lot of time working out optimum efficiencies and speeds by adjusting both the outdrive trim and trim tabs. In calmer seas trimming the drive out about 2/3+/- gives me the best speed/efficiency. It's not the most fuel efficient cruise speed, but she feels best about 27-28 mph. Most fuel efficient is 24-26.

In rougher seas I need to get the bow down a little bit to cut through the chop and smooth out the ride for passengers. I trim the drive to more like 1/4 - 1/2.

I've had this boat since it was new and the performance has been consistent. As I have played with the trim extensively, I don't know what else I could do. I always figured it was just a matter of the smaller 350 MAG. Any suggestions?

 

[b_arrington]

I looked up a test chart from Boating magazine.

The top end with the larger 6.2 MPI (320 hp) is 38.6 mph @ 4950 rpm. Since I have the smaller 350 MAG (300 hp), I always thought my max 32 mph @ 4800 rpm was pretty close, accounting for a bit less power.

 

[badtothebones]

On my 260, she is more fuel efficient at around 3800RPM/cruising~25knots/11GPH

WOT @ 38knots

 

[skibum]

Hehe.... I'll never see 2 MPG. I was going to answer the thread with "bad... and I love it".

The bad part about the 496 HO is the power curve is so damn high. It really shines at 4000 RPM, but man does she drink. I'm going to rename my boat to "Carbon Footprint".

 

[Lazy Daze]

I can't really offer any information as why the two of you have such a low top end speed based on the info in this thread, but I can tell you - from experience, and from working with Sea Ray for the last couple of decades - that 32MPH is not the norm. Take a look at Bennett's numbers - I would not doubt his numbers, or reliability on record keeping, for one second. His numbers match with the "norm".

Bad to the Bones... Just for reference, your 260 is not the same - it is a smaller boat than the 260DA or 270AJ referenced here and is a totally different hull.

 

[b_arrington]

Something is wrong there. That is WAY low. If you're using the trim properly, then you should have no problems getting quite a bit higher. You're RPM's are good, though... are you sure your speedo is accurate (or pitot not clogged)? Verify with GPS?

Yesterday I finally got the season's first ride on the boat. It was also the first ride since having the bottom blasted and repainted.

OMG, what a huge difference in speed from last year with the old paint to this year with a clean bottom. Last year I think my top speed in spring was about 30 mph. It was slower later in the year and I struggled to maintain my normal cruising speed. Any bottom growth just killed the speed too. Plus fuel burn was going up.

During yesterday's run I hit 36.7 mph at 4950 rpm, the fastest I've ever seen on my boat. This was with 1/2 fuel and full water too. I burned 22.2 gph at WOT, down a few mph from last year. 3600 rpm saw 26 mph, burning 12.5 gph, also a much lower burn rate vs. last year where I was getting about 16-17 gph at the same speed.

The boat had a much quicker hole shot, got on plane faster, and general felt more alive than it has in several years. I had the biggest stupid grin on my face as I was bombing around the Long Island Sound, turning gas into noise and speed.

 

[aerobat77]

when it comes to speed / burn comparisions i think we should only talk gps speeds to have a baseline . i also strongly believe some here mix up knots and mph . 32 mph at 4800rpm with a bravo drive and default props would mean severe prop slipping . 32 knots would match .

i have a 2006 240 sundancer with a 5.0 mpi and the utmost speed she can go is 64 km/h alias 40 mph alias 34 knots at 4800 rpm. that only with clean hull and very little fuel / water and just me on board .

i guess a 260 with the 350 mag will have a similar top speed light loaded.