anybody crusing with one engine off?

[Alex F]

I sent the email to ZF but haven't heard back yet. I'll be contacting SR as I want to find the true answer regarding mine transmissions as well, whether they can freewheel or not. I'm not sure if we have the same ones. Mine are ZF 280 1-A, Ratio: 1.769:1

I love watching their videos. Besides being entertaining you pick up some good tips here and there. I'm sure if you google or in youtube search for overnight cruising you'll pickup good links. I love watching some of the Nordhavn clips.

 

[Four Suns]

Wasn't their someone around here who was advocating turning off their moving car and coasting to a stop at red traffic lights to save gas? I could have sworn I saw that on this board somewhere....

 

[fwebster]

Wasn't their someone around here who was advocating turning off their moving car and coasting to a stop at red traffic lights to save gas? I could have sworn I saw that on this board somewhere....

Don't bother Sea Ray with a question specific to different transmissions and engines. It takes their time and the answer you will get is "Ask your transmisssion and engine manufacturer."

Besides, that question was answered here last year........whether or not the transmission clutches and bearings will sustain damage while free-wheeling is dependent upon the specific transmission model in your boat. So, you are on the right track on your transmissions....contact ZF.

Other considerations are that the Tides seals MUST have cooling water under pressure passing thru them. The Delrin seal body will wear very quickly if the seal body doesn't have water flowing. And, be very careful of extended idling with diesels. They are designed to be run under load. Unless your engines are down rated for long term operation at low power settings, extended idling will cause excess wear to the valve train and to gear driven accessory components. This also differs between engine makes and models.

 

[Hampton]

Tides Marine
Manufacturer of the SureSeal Self-Aligning Drip Free Shaft Seal

 

[VinceR]

Everyone has a different mission. Some days on the boat we may not crank the engines. Then there are days we explore and could run 6 to 10 hours. Most of our dinner cruises are 2 to 3 hours at "cocktail" speed. Our ocasional trip to Destin is 130 miles there and back. We may run that trip 1200 RPM with an occasional 1/2 hour run at 3500 rpm.

At 1200 RPM it is about 19 hours round trip. At 3500 RPM it is about 5 hour round trip if you discount the no wake zones.

With our slow and fast speeds we normally make it a 9 to 10 hour round trip. We do not round trip the same day.

I do not think operating on one engine is what I would do.

Concerning fuel burn, the good news is we do not have to drive these boats to work every day.

 

[Alex F]

Which version of the QSM-11 and what was the transmission ratio/prop size? Trawlers have their engines sized and transmission/props selected so they are running at optimal efficiency at displacement hull speeds. Not idling at 650 RPMs for hours on end. My boat runs at 6-8 knots at 650 rpms... which isn't too far from it's hull speed. At the published cruise RPM (2100), it moves along at 26-27 knots. Even the "fast trawlers" (ones that advertise cruising at hull speed OR planing) that have QSM-11's in them are such that their "fast cruise" speed is under 20 knots and hull speed is probably 8 knots or so... so when they are at hull speed, I'm betting they are turning 1200 RPMs or so... Also, some versions of the QSM-11 don't have turbos on them and are derated down to 400 something HP instead of over 600 HP like mine....

I stumbled on to this as a good example: http://www.boattest.com/boats/boat_video.aspx?ID=2781

I don't know if these have turbos or not. Are these your engines? "Std. Power 2 x Cummins QSM-11 - 715 mhp".

 

[timjet]

A quick way to determine if running single engine is more economical:
Set an rpm some where below hull speed say 1300 rpm on both engines and note the GPS speed. Shut one down and note the GPS speed. lf the speed on one engine is more than half the speed on two engines then it is more economical on one engine at that rpm.
On my boat I loose only 1.5 kts when I shut one down at 1300 rpm. Considerably more economical single engine below hull speed.