Running a Sea Ray 275/260 at say, 27 to 37mph for 5+ hour runs

Hi all, from Australia
I've just joined and would like to ask!

Is there a fast rev/speed that can be sustained for say, 6 to 8 hours?
I've read that 6-8knots is ok for fuel economy but I'm thinking of fast 5 hour runs at say, 15knots/27mph or even 5 hours at 20knots/37mph

I live in the Australian, Island State of Tasmania and we're situated in the Southern Ocean roaring 40's and Bass Strait. There is nothing but southern ocean between Tasmania and South America so we get crazy westerly weather and a lot of rough weather BUT! we also get some fantastic boating weather on our East Coast.
It's the fantastic boating weather days that I'd like to do some extended express cruising to the sheltered East Coast anchorages for weekends or a week or two weeks exploring.
We have lots of outlying islands but it would be nice to hustle to them to make the most of the calmer waters.

I'd ideally like to sustain 15-20knots/27-37mph, even 40mph runs at 3+hrs then throttle back to 27 to 37mph for the remainder.
This would give me some excellent travel distances to our outlying Islands or coastal bay anchorages and once there I can then casually and leisurely explore the closer outlying Islands or if the weather turns bad I can hustle to a more sheltered shore and get away from a lee shore.

Given that I would like to do day hops to anchorages and in good weather is a Sundancer 275/260 up to travelling and sustaining 5 - 6 hour runs?

Cheers all, Pete
Oh, as much as I'd like a bigger Sea Ray my budget will only support a 2006 to 2008 Sundancer 275, I like the styling, there is only myself and my girlfriend, our children are all grown and if they want to come boating we'll keep the family boating to daily exploring, fishing or swimming.
My partner and I would like to explore farther along our coastline but as mentioned we will need to maintain 5hour runs to keep up with safe distances of safe anchorages should the weather turn for the worse or we need to beat the inclement weather.

Cheers again, Pete

15-20knots would be 17-23mph. Using a '06 260DA for an example you only have about 80 gallons of fuel. Depending on which engine, you'd be burning about 12-16 gallons per hour when at a good cruise speed, about 3500rpm. I don't have a boat like this but would guess 3,500rpm would be in the area of 28-30mph. Trying to run 35-40mph will eat your fuel up.

If you're making a 5-6 hour run on plane there needs to be a gas pump at your destination.

General rule is 75% of your WOT rpm.

Woody said:

15-20knots would be 17-23mph. Using a '06 260DA for an example you only have about 80 gallons of fuel. Depending on which engine, you'd be burning about 12-16 gallons per hour when at a good cruise speed, about 3500rpm. I don't have a boat like this but would guess 3,500rpm would be in the area of 28-30mph. Trying to run 35-40mph will eat your fuel up.

If you're making a 5-6 hour run on plane there needs to be a gas pump at your destination.

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Thanks for the reply, I really had no data to go from. I did find some fuel consumption data in Litres from Boat-Fuel-Economy website which had the Mercruiser 5.7MAG - 300HP @ 1500rpm = 9.5L 3000rpm = 28.5L and 3500rpm + 37.5L but I'm unsure how accurate those internet figures are and would rather get 'real data' from owners.

There are gas pump docks at each of my 5hr stopovers and I'll carry another 200L secured in the engine area. That's a lot of explosive fuel in the engine area but I think secured well, in good-quality fuel containers or an aux holding tank will be ok.

Have a serious buyer on my yacht today and finalising the change over paperwork so hopefully, I'll have local a Sea Ray 275 purchase done in a month as I'm helping crew my yacht to her new home port.

scoflaw said:

General rule is 75% of your WOT rpm.

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Thanks, some really valuable information.
Is 75% of WOT a good cruising speed?

I'll get into more forum searches and have a more detailed read of some posts.

Our 2006 260DA w/ 350 Mag cruised at 3800rpms(75%), 27mph, and consuming 13.5gph. This was 2 people, full water and fuel, with gen and ac loaded for a weekend.

That would give you 4-5 hrs of run time with a 25% safety factor on the fuel.

Bennett

Most efficient cruise for me with the 350 MAG is 3600 rpm, 24-25 mph and 11-12 gph. I'm more comfortable at 27-28 mph, 3850 rpm burning 16-17 gph. That assumes seas of 0-1.5.

Since you mentioned the rough Southern Ocean, Keep in mind the 260/275 DA is NOT an ocean going vessel. It is an inshore vessel built to Type C standards. Sea Ray lists operating conditions as:

C. Inshore
Maximum wind speed: 27 knots (31 mph)
Maximum wave height: 2 meters (6.5 feet)
Boat use is limited to coastal waters, large
bays, estuaries, lakes and rivers.

bbwhitejr said:

Our 2006 260DA w/ 350 Mag cruised at 3800rpms(75%), 27mph, and consuming 13.5gph. This was 2 people, full water and fuel, with gen and ac loaded for a weekend.

That would give you 4-5 hrs of run time with a 25% safety factor on the fuel.

Bennett

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Hi Bennett,

Thanks, that's great first-hand information, do appreciate it.
Cheers, Peter

Hi all,
Thanks for the wealth of good information. I've formulated some data and using Navionics my maximum run at 27mph is just over 3hrs at a fuel consumption of approx 173L. This is a good safety margin of fuel as each of my ports of call have fuel docks available. Plus running Unleaded fuel I've a greater chance of using jerry cans to transport fuel from the local gas station, albeit, that's a tough way to transport fuel but at least it's an option.
I like to have a 3/3 rule of 1/3 fuel to destination/1/3 for a return home and 1/3 in reserve and the 3hr run isn't a 1/3 but it's an acceptable 1/2 tank and I'll most likely have a spare 100 to 140L in fuel safe 20l containers secured in a secure holder.

Hopefully, it looks like my yacht has sold but nothing is ever sold until the money is in the bank...once my yacht is sold I'll invest in a Sea Ray 275 (Sea Ray 260 in the USA). there is a nice 275 for sale about an hour from my location.
I've got a private, locking gate, 9mtr/30 foot floating pontoon berth with 240v power and water. Our local club only charges members $60 Aud (approx $48US) to haul out in winched cradles and the same price to put back into the water. Hardstand use is $15 AUD (approx $12US) per day with 240v power, water and a complimentary 1.5hr use of the high-pressure cleaner. I'm thinking an annual haul out will not be expensive and maintaining the 275 looks reasonable.

Cheers, Peter

b_arrington said:

Most efficient cruise for me with the 350 MAG is 3600 rpm, 24-25 mph and 11-12 gph. I'm more comfortable at 27-28 mph, 3850 rpm burning 16-17 gph. That assumes seas of 0-1.5.

Since you mentioned the rough Southern Ocean, Keep in mind the 260/275 DA is NOT an ocean going vessel. It is an inshore vessel built to Type C standards. Sea Ray lists operating conditions as:

C. Inshore
Maximum wind speed: 27 knots (31 mph)
Maximum wave height: 2 meters (6.5 feet)
Boat use is limited to coastal waters, large
bays, estuaries, lakes and rivers.

Click to expand...

Thanks for the info,
Tasmania is situated in the southern ocean with huge, no, HUGE westerly swells (Google Marrawah Tasmania to give you an idea of Tasmania's rugged West Coast) thus, I'll be staying well clear of the West Coast and limiting my cruising to the much calmer Eastern side of Tasmania which is usually our 'tourist' coast of sunny days and generally calm seas. Like all coastal seas, rough weather can happen but the ability to 'outrun' it is what I like in these boats.

Thanks and cheers, Peter

Peter Williams said:

Thanks for the info,
Tasmania is situated in the southern ocean with huge, no, HUGE westerly swells (Google Marrawah Tasmania to give you an idea of Tasmania's rugged West Coast) thus, I'll be staying well clear of the West Coast and limiting my cruising to the much calmer Eastern side of Tasmania which is usually our 'tourist' coast of sunny days and generally calm seas. Like all coastal seas, rough weather can happen but the ability to 'outrun' it is what I like in these boats.

Thanks and cheers, Peter

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I assume you have good experience since you are selling a yacht to buy the sea ray. But my advice is never think you can "outrun" bad weather in any boat. That will just get you into trouble. The fact is that the weather you are trying to outrun will be moving faster than you are AND will be slowing you down as it approaches. Watch the forecast very closely and don't go if the weather forecast is outside of the capability of the boat and/or your experience.

Creekwood said:

I assume you have good experience since you are selling a yacht to buy the sea ray. But my advice is never think you can "outrun" bad weather in any boat. That will just get you into trouble. The fact is that the weather you are trying to outrun will be moving faster than you are AND will be slowing you down as it approaches. Watch the forecast very closely and don't go if the weather forecast is outside of the capability of the boat and/or your experience.

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Hi and thanks,
Yes, I have very good sailing experience and with that, I'd like to say excellent navigation skills and weather awareness skills.
I guess to clarify 'outrun' is that I'd cruise to the appropriate weather but should weather look like it's turning for the worse either by our Beaurea of Meteorology forecast, local knowledge, observable weather or indeed all of those then I'd run for cover, hence, my I'd outrun the weather is simply to run for cover before the weather turns.

Cheers again, there is some brilliant advice on this forum.
Pete

You probably know this but I did not see it mentioned. The 75% of WOT is a good rule of thumb for cruising RPM, and it also assumes your boat has the proper prop installed. A proper prop is one that allows your engine to reach the maximum RPM which is specified by the engine manufacturer. If you can only reach an RPM that is lower than the engine spec, you will overload the engine and shorten its life. Marine engines in good condition are very robust when used properly. We routinely cruise for 10-12 hours at a time and do not worry about the engines.