Twin engine skippers - single engine ops possible?

[QC]

Re: Twin engine skippers - single engine ops possible?

My wallet doesn't care about gph. It cares about mpg. That's how I measure fuel efficiency.

OMG. I love you man!!! Pet peeve and I have been bashed for suggesting that GPH is meaningless data without speed. With speed you have MPG

 

[rbh]

Re: Twin engine skippers - single engine ops possible?

That's a whole 'nother debate - BTDT!

BAAHAHAHA, kinda like poken the wasp nest isn't it!!!
(WUZ BTDT?, have not learned all the internet lingo yet.)

Anyways controling your speed in a low/no wake zone with your twins going can be a bear, sometimes cutting your speed by using just one engine is best, mindya like I mentioned lots of course corrections.

 

[The Famous Grouse]

Re: Twin engine skippers - single engine ops possible?

I think Fireman essentially has it correct in that this issue of trailing an engine is a complicated question that cannot be answered by armchair analysis.

This question and LOTS of subsequent discussion comes up frequently in trawler or long-distance cruising forums. I'm certainly not an expert, but from what I've read, you must have all the specifics of the equation to get an exact do/don't do/how to do answer. Every engine/drive combination has different requirements.

It certainly IS possible, but as others have pointed out and from what I've read on other threads, the results as far as fuel and wear/tear savings vary widely. Some of the long-distance cruisers report fuel savings and some of them report the opposite. Many of these folks have fuel flow meters, so I don't question the reports. It just goes to show that it's a complicated issue.

Grouse

 

[QC]

Re: Twin engine skippers - single engine ops possible?

I think Fireman essentially has it correct in that this issue of trailing an engine is a complicated question that cannot be answered by armchair analysis.

Agree, despite my engine efficiency comment.

you must have all the specifics of the equation to get an exact do/don't do/how to do answer. Every engine/drive combination has different requirements.

100% agree. Add in "application" to the Every part.

Some of the long-distance cruisers report fuel savings and some of them report the opposite. Many of these folks have fuel flow meters, so I don't question the reports. It just goes to show that it's a complicated issue.

100% agree. Great post!

Edit: BTW, I think there are a TON of examples of IB trannys (Velvet Drives+) being towed in Neutral. Think Houseboat

 

[25thmustang]

Re: Twin engine skippers - single engine ops possible?

And you probably have v drives? Never seen 4 controls for I/O's.Never

I was under the impression the post was about I/Os and Inboards, which is why I commented that not every boat this size has two controls (one controlling both trottle and shifting for each motor). It also sounds as though I/Os may be optioned with seperate shifters. Not trying to start a debate, just felt that a statement seemed false and was hoping to correct it.

 

[haulnazz15]

Re: Twin engine skippers - single engine ops possible?

There are obviously several variables here, but I would imagine at speeds of less than 10mph in protected areas like locks (as the OP mentioned), it seems like there wouldn't bee too big of a strain by running only one screw. Mainly because we aren't trying to get on plane or remain on plane here, just moving at some speed above idle. The only major thing I'd assume would be cause for running both is the tranny lube issue on an inboard, the I/O's wouldn't care, although I'd put the drive in FWD to relieve a windmilling prop as it would create more drag than having a stationary one.

 

[Fireman431]

Re: Twin engine skippers - single engine ops possible?

And I respectfully disagree with this . . .

This is a very complicated discussion, but speaking of engines only, gasoline engines, this is backwards. If "efficiency" is the use of fuel to produce output, they are most "efficient" with more load at a given RPM, than less. So the 50% thing is kind of off.

OK...I'll clarify with my experience. First by efficiency, I meant MPG on one engine burning, pushing the boat, not 'true' efficiency regarding fuel use vs. power/torque out put, so I see your point.

I ran 12 miles on on engine due to a blown oil cooler. As a rule, with both engines running at 1500 RPM, I average 9 MPH at a rate of 6 GPH burned by the engines (total fuel use).

When returning on 1 engine, running 1500 RPM to maintain steerage, I was burning 7-8 GPH on one engine and moving along at 5-6 MPH. Of course, I wasn't concerning myself with the current on the outgoing or incoming trip, so there are some X-factors to deal with, but you can see by this one example that running on one engine slowed my speed by almost half while burning more fuel.

 

[QC]

Re: Twin engine skippers - single engine ops possible?

Totally agree, and understand!!

OK...I'll clarify with my experience. First by efficiency, I meant MPG on one engine burning, pushing the boat, not 'true' efficiency regarding fuel use vs. power/torque out put, so I see your point.

Thank you for a quality reaction. I often post simply for clarity, and it tends to pizz people off. I really appreciate you noting that I was clarifying the words, not the intent. Thanks!!

 

[Philster]

Re: Twin engine skippers - single engine ops possible?

Leave the center one down and running.

 

[Thalasso]

Re: Twin engine skippers - single engine ops possible?

Then you've never seen a go fast with Twins. They all have four controls and I/Os where I boat

Yes more common above 28 ft. with Inboards, but not exclusive.

Then why would you try to debate an issue the op has with your irrelevant boat.

 

[Thalasso]

Re: Twin engine skippers - single engine ops possible?

My 1981 Sea Ray (rebuild project) had separate shifter and throttle controls with twin i/os. The Cruisers 2870 I had was twin I'll
/o with combined throttles/shifters. It seems a question of personal preference, or just what came on the boat. Neither configuration has any effect on the OP's question.

For that, I have to go with the fact that one engine, not driving the boat from the center, creates side torque that has to be overcome by steering back, which costs fuel. My wallet doesn't care about gph. It cares about mpg. That's how I measure fuel efficiency.

Are they not rellevant. GPH=MPG

 

[Thalasso]

Re: Twin engine skippers - single engine ops possible?

I was under the impression the post was about I/Os and Inboards, which is why I commented that not every boat this size has two controls (one controlling both trottle and shifting for each motor). It also sounds as though I/Os may be optioned with seperate shifters. Not trying to start a debate, just felt that a statement seemed false and was hoping to correct it.

V Drives are as close to true inboards as you can get.

 

[sschefer]

Re: Twin engine skippers - single engine ops possible?

I could run it if I had to but no it was not running. Smog Cops are tough on San Francisco Bay and this thing (650 Detroit two stroke) was blowing black smoke like a 1000 car freight train. If you are unsure of how your system is setup and you just want to try it out then leave the motor running and out of gear. Personally, I can't see any significant fuel savings and you'll be fighting the boat the whole time. The increased drag from the extra steering you'll need to put on + the dragging wheel will probably negate any fuel savings. And besides, it takes all the fun out of it.

 

[CaptainKickback]

Re: Twin engine skippers - single engine ops possible?

Are they not rellevant. GPH=MPG

Are they not rellevant. GPH=MPG

I've seen these gph discussions many, many times, but always stayed quiet and shook my head. I'm with qc on this one. If you tell me only a gph figure, and maybe even an rpm figure, it tells me nothing. You will argue it does, but I don't know what it is you were telling me. How far did you go, how long did it take, or what was your speed. Add any of these figures and now I have meaningful information from which to make an assessment.

If you tell me you engine burns 6 gph at wot so what. If you're going 40 mph, you've got great performance. If you're going 10 mph, your boat's a dog.

Sorry, but you did make 3 contradictory posts in a row, on 3 different sujects, so I have to wander about motivation.

 

[scoutabout]

Re: Twin engine skippers - single engine ops possible?

Thank you all for the thoughtful replies. At least I don't feel so sheepish about wondering all this time. I can see it isn't as simple as one might think.

 

[25thmustang]

Re: Twin engine skippers - single engine ops possible?

V Drives are as close to true inboards as you can get.

Umm... V drives are true inboards... Unless I'm misinformed but my v drive boat and my straight drive boat are both true inboards. Inboards were asked about in the original question, along with I/Os.

Sorry to derail.

 

[NSBCraig]

Re: Twin engine skippers - single engine ops possible?

The gph thing has always seemed funny to me too.

Does it matter if you burn half the fuel I do in an hour if I'm at the destination in an hour and it takes you three?

Sure it's a stat and all data is good, but it's one of those things that unless you have "the rest of the story" doesn't mean much.

Then you always have cost of fuel per year thing.

 

[Thalasso]

Re: Twin engine skippers - single engine ops possible?

Umm... V drives are true inboards... Unless I'm misinformed but my v drive boat and my straight drive boat are both true inboards. Inboards were asked about in the original question, along with I/Os.

Sorry to derail.

It was being a little sarcastic.