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Old 09-19-2017, 06:24 AM   #41
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Yes, 4 gallons for both

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Originally Posted by Art View Post
Gordon

You do mean 4 gals. per hour - per engine... for twin cummins 330s, at 8.5 kn. Right?? Or, are they using only 2 gals. per hour each???

"My fuel burn rates on my Ocean Alexander 456 approximated 4 gallons an hour"
Art,

Yes, 4 gallons for both engines. It was a small fraction over 4 gallons. This included some slower speed's in the Florida ICW for manatee zones and no wake zones. But it also included a couple of ocean Jogs, Fernandina beach to Charleston, and Wrightsville beach to Beaufort, where our speeds were closer to nine knots.

I was quite pleased with the boat's fuel consumption rate.

In a couple weeks we will start out for the Bahamas. This will give me another opportunity to monitor fuel burn rates over long distances.

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Old 09-19-2017, 06:25 AM   #42
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I can see that English grammar got in the way again. What I meant to say was 2 gallons per hour, per engine.
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Old 09-19-2017, 10:09 AM   #43
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I can see that English grammar got in the way again. What I meant to say was 2 gallons per hour, per engine.
Very economical!
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Old 09-19-2017, 11:15 AM   #44
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The fuel burn single v/s twin difference isn't worth talking about and can swing either way despite what people say. However the twins w double the power will almost always burn more fuel because the owners will run them faster. And if you have a GB36 w twin yanmars that are slightly more efficient .. that boat may burn less than a GB36 w a single FL or Perkins.

If I was buying a GB36 I would only look at singles for a number of reasons but if I could choose the engines I'd definitely buy a twin.

Also IMO the old wifes tale about twins halving twice the maintenance is just passing along a rumor or wifes tale. But the tale applies to twin engines v/s single whereas the engines all are the same size. And a proper twin would have engines half the size of it's counterpart single and maintenance would be almost exactly the same. But for the boats we're talking about most of the time .. maintenance is actually about double.
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Old 09-19-2017, 03:14 PM   #45
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One of the advantages of a single engine boat is the protection the keel gives to the propellor and rudder.

In the PNW, with the amount of floating logs and crab pots, I'd be a little concerned about having 2 unprotected props. But if your lucky, you may still be able to get home on one engine.
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Old 09-19-2017, 04:40 PM   #46
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IMO the old wifes tale about twins halving twice the maintenance is just passing along a rumor or wifes tale.
I think twice the maintenance is about right. Double the engine oil change, double the oil filter change, double the fuel filter change, double the transmission oil change, double the oil cooler replacements, double the stuffing box overhauls etc.

Repairs are another story. It is highly unlikely for both alternators to croak simultaneously. ditto for raw water pumps, fresh water pumps, transmissions, injectors, starters.

I have driven many hundreds of thousands of miles in a single engine car. I'm still alive. I don't see a boat engine as all that different. I am happy with the increased reliability and better maneuverability that my twins offer. The cost of the extra fuel is not a major factor. I could always anchor out more if I needed to keep expenses down. Fuel expenses are tiny compared to summer/winter storage fees.
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Old 09-19-2017, 04:56 PM   #47
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Re. The GB36 specifically, owners report a solid continuous Max cruise of just over 16kts on twin 210hp Cummins ; impressive for a 12 tons trawler. Its a surprisingly efficient hull at 30hp/ton equaling the new Swift trawler34, as it actually planes without pushing a massive wall of water in front of the bow.

With twin 120hp Lehman's it will still manage 11-12kts for 'a run for shelter' option if you get caught out in worsening conditions.

The 32' is a displacement hull, and the 42' is a huge bulldozer; the 36 is the ballerina

PS: from my recent research, I don't own one.
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Old 09-19-2017, 05:29 PM   #48
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Rusty wrote;
"With twin 120hp Lehman's it will still manage 11-12kts for 'a run for shelter' option if you get caught out in worsening conditions."

Made possible probably by the well fwd heavy engines. May be a handful in following seas though. The 32 is a SD hull.
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Old 09-19-2017, 05:35 PM   #49
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Quote:
Originally Posted by AusCan View Post
One of the advantages of a single engine boat is the protection the keel gives to the propeller and rudder.

In the PNW, with the amount of floating logs and crab pots, I'd be a little concerned about having 2 unprotected props. But if your lucky, you may still be able to get home on one engine.
I`ve not seen one here but if memory serves there are US twins boats with rudder/prop protection. Gulfstar and maybe one other come to mind, just from pics and posts on TF.
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Old 09-19-2017, 05:46 PM   #50
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We have twin 330's and at 8K burn a total of 4 to 4.5 gallons/hour depending on conditions. LWL 46.8, weight 32,000 lb. So long as we stay under hull speed economy is good. I doubt a single of any HP would do better enough to make fuel burn an issue. Weight extra maintenance and room in the engine room and keel configuration with prop protection would be the basic pros of the single not fuel. Flemmings cross oceans with twins and when they tested single against twins found fuel a non factor.
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Old 09-19-2017, 05:49 PM   #51
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I`ve not seen one here but if memory serves there are US twins boats with rudder/prop protection. Gulfstar and maybe one other come to mind, just from pics and posts on TF.
There are a few twins around with protected props but not GB's.

Here's a nice Tassie built boat with twin keels.
https://yachthub.com/list/boats-for-...seas-63/206958
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Old 09-19-2017, 05:57 PM   #52
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There are a few twins around with protected props but not GB's.

Here's a nice Tassie built boat with twin keels.
https://yachthub.com/list/boats-for-...seas-63/206958
Marlow explorer
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Old 09-19-2017, 06:19 PM   #53
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Want to mention a pretty sizable misconception regarding calling it 2X the maintenance work-time for twins compared to a single.

When you do service needs such as oil change, coolant refreshment, fuel filter change etc... it's the time spent purchasing products to use, gathering tools to do the project, getting up close and personal in the engine compartment, cleaning up at end of service performed, dumping old product for recycling or flat out trash and putting tools away... that takes just about the same amount of time to do for two engines as it does for one.

That said - I agree that during the actual service performance on each engine it doubles that time spent. But... much of the time spent to accomplish service happens before and after the service itself instead of during the actual on engine service procedure. Therefore twins are no where near 2X maintenance time compared to a single. Of course, service product cost is 2X.

So, I conjecture... for twins it takes maybe 1.2 to 1.3 more time to perform entire general service procedures than on a single. To say twins are 2X the time for servicing is way overboard. Pun intended!

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Old 09-19-2017, 06:28 PM   #54
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We have twin SP 225's in our President 41. As to prop protection with a single or twins, I always thought that twins were very easy to damage the props with submerged debris as compared to a single. We have a fairly large keel with exposed props. Last year coming up the Hudson River, we hit submerged debris at least 12 times that could be felt all the way up to the flybridge. There was a tremendous amount of floating debris as well as submerged. I was sure that our props would be mangled and have to be rebuilt. After the 1400 mile trip home and countless strikes of submerged debris, when we hauled the boat for the winter, there was absolutely no damage to either prop. Now I am not so sure about the single vs twin prop protection theory...
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Old 09-19-2017, 08:01 PM   #55
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We have twin SP 225's in our President 41. As to prop protection with a single or twins, I always thought that twins were very easy to damage the props with submerged debris as compared to a single. We have a fairly large keel with exposed props. Last year coming up the Hudson River, we hit submerged debris at least 12 times that could be felt all the way up to the flybridge. There was a tremendous amount of floating debris as well as submerged. I was sure that our props would be mangled and have to be rebuilt. After the 1400 mile trip home and countless strikes of submerged debris, when we hauled the boat for the winter, there was absolutely no damage to either prop. Now I am not so sure about the single vs twin prop protection theory...
That's quite the "lucky" story. How fast were you traveling through the water when items hit the boat? Slower the better... as the items will tend to be pushed to the side unless you were traveling quite fast. Semi submerged items are less likely to be pushed aside and can become a problem regarding hitting a prop.

In 1960's I traveled through Hells Gate quite a few times heading up the Hudson for delivery of twin screw boats. Man, there was a lot of junk of every type and the current caused eddies that some times swirled debris in circles. I can still clearly see the poles, pallets, tires and other debris in my mind's eye, Reason I recall that so vividly is because being a young teenager I was often on the bow leaning on a bow rail yelling back to the captain, my dad, what was coming up and which way best to slightly turn the boat. Many times I just pointed and he turned that way.

I do not recall any prop damage. I do know that we were going slow as possible while still making headway against the strong current. Obviously slow enough to push debris aside.
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Old 09-19-2017, 08:07 PM   #56
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We were doing 10 knots.
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Old 09-19-2017, 08:16 PM   #57
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twin owner here.

next boat will be single. have run home after a minor failure too.

fuel not a consideration can run 1 engine at a time and get close..

top speed, meh, thought it was important.. nice to have but not required.

2x the maintenance is a consideration that can't be ignored.
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Old 09-19-2017, 10:16 PM   #58
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twin owner here.

next boat will be single. have run home after a minor failure too.

fuel not a consideration can run 1 engine at a time and get close..

top speed, meh, thought it was important.. nice to have but not required.

2x the maintenance is a consideration that can't be ignored.
You mean 2X parts cost [which is minimal regarding annual expenses] or is it time spent you mean by 2X?

Please read Post # 23.
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