Twin 7.4 fuel economy

[BruceD]

I am thinking of buying a 33' Sun Dancer with twin 7.4 mercs. Am I nuts? Will the fuel costs be overwhelming?:smt021

 

[Hampton]

I am thinking of buying a 33' Sun Dancer with twin 7.4 mercs. Am I nuts? Will the fuel costs be overwhelming?:smt021

I'm guessing late 90's? Fuel consumption will probably be around 25 - 28 gallons per hour at cruise. Cruise speed will be about 25 mph. Approx 1 mpg. Any owners up yet?

 

[Larry]

Basicly what Hampton said.... I run @3200 RPM / 24 kts / 28 GPH / .95+ MPG

Props are well tuned and perfectly balanced...

 

[fc3]

Old chart, but these are actual values read from the EFI analyzer.

Best regards,
Frank

 

[sprink56]

Old chart, but these are actual values read from the EFI analyzer.

Best regards,
Frank

Thanks for sharing this....first time I have seen this one. I looks spot on. I wonder if anyone has put a spread sheet together for this?

 

[Air O'Nautical]

I am thinking of buying a 33' Sun Dancer with twin 7.4 mercs. Am I nuts? Will the fuel costs be overwhelming?:smt021

Of course.
Yes, your nuts.
Fuel is still the cheapest part of boating...it just hurts to see the cash go soo quick.
Good Luck..

 

[Kameroo]

Of course.
Yes, your nuts.
Fuel is still the cheapest part of boating...it just hurts to see the cash go soo quick.
Good Luck..

To tag on to what he said, look at how you'll be boating. We have a pair of 454s that get horrible mileage. But, we're on a river and don't have to go very far for a good weekend. The fuel bill is a fraction of the total cost of ownership.

 

[Glen S]

We just recently bought our 400 DA and don't have many miles / hours under our belts yet. She is running twin 7.4 MPI's and we seem to be looking at about 1 Nm / gal at 3000 RPM and about 20 knots - so in the 20 - 22 gal/hour range. Yea, it isn't cheap but we figure we only really use fuel on a trip somewhere for a week-end or vacation and the costs of hotels and every meal out would likely be the about the same and we have way more fun on the Sea Ray....at least that is how we rationalize it :grin:. I say go for it!

 

[rcknecht]

To tag on to what he said, look at how you'll be boating. We have a pair of 454s that get horrible mileage. But, we're on a river and don't have to go very far for a good weekend. The fuel bill is a fraction of the total cost of ownership.

I also find the cost of fuel insignifcant compared to maintenance and storage, but if you think too much about the cost of boating you will not be happy... It is a life style, and nothing is nicer that fendering up with friends on the week end. It is one place were both kids and adults can have fun while getting away from life's problems... If fuel is an issue, go slow and stay close to home...

 

[BruceD]

I agree with your comments. Thanks. Just wanted verification that yes, I am nuts, and life in general is costly. Enjoy it and be thankful I say. I'll be on the water again soon. Happy boating to all my Sea Ray friends.
Bruce

 

[Sundancer]

Fuel cost? There is a fuel cost associated with these "boat" things? Shoot, after the initial purchase price, survey (even if it's new!!), 50 and 100 hr service, marina, moorage, bottom paint, annual maintenance, insurance, Vinyl name, cleaning, waxing, divers to clean the bottom, tow vehicle costs (if equipped!), new curtains, new dishes, fitted sheets, , matching towels, Magma (or equivalent) grill, cooler, better mattress and MORE fitted sheets, new microwave, electricity at the marina, Sea Tow, transient slip or park moorage costs, spare parts, spare props, anchors, rode, dock lines, snubbers, fenders, life jackets, fishing devices, towable, devices, radar, depth finder, stereo, dinghy, davits, outboard, etc., the fuel cost is NOTHING! :grin: The good thing is the cost of the 7.4's is way less than a couple of diesels and will go a whole lot faster than 6.2's or 350's!!

 

[Hampton]

From your list, I did not buy new fishing gear, snubbers, spare props, radar, or depth finder, but I'd like to add 2 new tvs, 3 amps, 2 subs, 6 other speakers, dinghy cover, camper canvas (1 1/2 times), licensing, cleaners, compounds, waxes, orbital buffer, rotary buffer, dinghy name plate, dinghy locks, dinghy engine locks, gel coat, zincs, new heat exchangers, fresh water cooling apparatus, pots, pans, NO new microwave, but 2 new coffee pots, NO new stereo, but a new set of cockpit carpeting. That got us started. There is no way I'm going to change boats this year!!!!!!!!!!!!!!!!!!

 

[Plane 2 Sea]

We have a '96 330 Sundancer with carb'd 7.4l/454's, run 28 gal.per hr thru her at 3100 rpm's, gets us 23.5/24 kts. Love the boat!! She'll do 33+ kts wide open, that fuel burn gets a little scary, but not necessary. Good luck.

 

[Alegria]

I am late to the party, but all the posts are in line with what I see. 28gph at 3100 30gph around 3200 and 23-25K depending on the RPM. I like the slower cruise as it is a much gentler motion for me on the bay. With the 17degree deadrise I do get a hard landing sometime in the chop of the bay! The boat feels right to me at 3200 RPM but last weekend I ran her just over 3000 with some serious tabs and found the fuel burn to be a bit lower...

Fuel is a normal cost of boating. With our late model 97 there are so many other things to spend money on, upgrades, fiberglass repair/refresh, mechanical items to replace... Well fuel is not out of line.

 

[VinceR]

SEA RAY 340​

2001​

PERFORMANCE​

“WILD RICE”​

TWIN 454 MPI​

​

Speeds by GPS
Fuel Flows by computer connected to engines.

RANGE IS 215 GALLONS

RPM MPH GPH MPG RANGE

700 3.9 2.0 1.95 419

1000 6.0 3.6 1.66 358

1200 6.8 4.4 1.55 333

1500 7.9 7.0 1.13 242

2000 12.4

2500 18.6

3000 16.9 24.0 .70 150

3200 20.5 26.6 .77 164

3400 24.1 30.6 .79 168

3500 25.0 31.0 .80 172

3600 26.4 33.4 .79 170

3800 28.0 34.8 .80 172

4000 29.5 38.0 .77 164

4300 32.6 47.6 .68 147

 

[fc3]

SEA RAY 340
2001
PERFORMANCE
“WILD RICE”
TWIN 454 MPI
​

Speeds by GPS
Fuel Flows by computer connected to engines.

RANGE IS 215 GALLONS

RPM MPH GPH MPG RANGE

700 3.9 2.0 1.95 419

1000 6.0 3.6 1.66 358

1200 6.8 4.4 1.55 333

1500 7.9 7.0 1.13 242

2000 12.4

2500 18.6

3000 16.9 24.0 .70 150

3200 20.5 26.6 .77 164

3400 24.1 30.6 .79 168

3500 25.0 31.0 .80 172

3600 26.4 33.4 .79 170

3800 28.0 34.8 .80 172

4000 29.5 38.0 .77 164

4300 32.6 47.6 .68 147

Some of your speeds seem a little slow. I get 26-27 knots at 3400 RPM. WOT isn't far off the mark, but again, a bit slow I get mid 30 knots. Is the bottom dirty or do the props need tuning?

 

[carterchapman]

From your list, I did not buy new fishing gear, snubbers, spare props, radar, or depth finder, but I'd like to add 2 new tvs, 3 amps, 2 subs, 6 other speakers, dinghy cover, camper canvas (1 1/2 times), licensing, cleaners, compounds, waxes, orbital buffer, rotary buffer, dinghy name plate, dinghy locks, dinghy engine locks, gel coat, zincs, new heat exchangers, fresh water cooling apparatus, pots, pans, NO new microwave, but 2 new coffee pots, NO new stereo, but a new set of cockpit carpeting. That got us started. There is no way I'm going to change boats this year!!!!!!!!!!!!!!!!!!

+1 John!

 

[VinceR]

Well FC3 you pose a good and reasonable question. My bottom was clean and the props are original with about 375 hours on them at the time of my test. I only did the test to satisfy my own curiosity. I only post the results to show how my boat performed on that particular day. We had three men on board, almost full fuel tanks, full water and about half full black water tank. We were in fresh water. It has been my observation that as we burn fuel the boat performs better. I think the fuel flows are good for all 7.4 MPI engines at those particular RPMs. However, speeds would vary with different boats, weights, bottom conditions and prop condition.

I am not an engineer, nor an expert on gasoline engines or boat performance. I am out playing with my boat and trying to learn what I can about its limitations and performance. We may take off on another trip one day.

 

[fc3]

Hi Vince

We have the same hulls, but the topsides are different. Did a number of speed checks on the way to and from the Atlantic City meeting this spring. Full fuel, full water, empty holding @ 3400 she turned about 25-26 knots. With less than fuel she was in the 26-27 knot range. I had my props tuned by a PropScan shop in 2005 to Class 1 ISO spec. Maybe having the props tuned made the difference.

 

[VinceR]

FC3

Last weekend we were in Madisonville, LA on the Tchefuncte River at Marina Del Ray. Madisonville is across the lake from New Orleans. I saw a 330 like yours parked next to a 340 like mine. They are almost the same boat. I probably need to have my props reworked or even better install a couple of 4 blade props. I do not have fuel flows. We used the Mercury computer reader to monitor fuel flow for the test. The 330/340 Sundancers are real nice boats. I took mine out today for a short cruise. Spent the majority of the cruise at 1200 RPM.