Fuel costs and Running on 1 engine

[zentodd]

I know several of you run on 1 engine for efficiency. I’m concerned that the other engine’s transmission would not get lubricated. Is this a problem? If yes, how do you handle this? Strap the off engine shaft somehow? Or run the “off” engine at idle in gear?
Thanks in advance!
PS - I’ve also heard someone advising to run at 60% off total max horsepower not rpms for best engine life. How does one know the horsepower being used?

[Uncle_Bob]

My ZF tranny manual says no issue if tranny turns without power. If economics had me run on one engine, I'd get a new hobby.

[zentodd]

Well i looked my Hurth tranny manual and yes it can turn at trolling speed without hurting the transmission. Thanks.
As to the snarky comment about economics - that’s my reality. My guess is it’s most peoples reality. Just because we have a big boat doesn’t mean we have endless pockets. When i look at the cost of a multiple month trip up North to Canada and the cost of fuel has essentially doubled - well maybe I’ll slow down a bit. Maybe I’ll get creative and run on one engine if It helps me make the decision to take this adventure with my family.
Thanks again.

[Uncle_Bob]

Sorry for snarky. OK try this: Run on one engine you affect things. For example offset steering means more meandering (yeah less an issue with autopilot) It means no hot water or no battery charge depending which engine. Point is, there are trade offs and actual cash savings might be negligible, especially with the wear and tear concentrated on one engine. Diesel in Canada is around $2.25/litre. That's about $US6.75/gallon. Hope this helps. Maybe someone running on one engine can tell us how much they really save.

[zentodd]

Good points. Many thanks again:-)

[Gabonchulous]

Perhaps you could tune things mechanically and operationally to handle (most of) these things? If you have 2 alternators, you could probably work out a way to direct the charging where you wish. Then, you could alternate between engines perhaps per day. When travelling relatively long distances like Portland, OR to Anacortes, WA would be about $2500 @ 1gph. All that being said, I would be curious how much drag a non-feathering prop and offset rudders would cause vs just running both at < 1000 RPM.

[MacPhid]

Zen, you nailed it when you said slow down a bit. On our 38, that means under 7 knots, less than 6 if you really want to save fuel. Look out the back of your boat underway, if you're creating any white water from your wake, you're going too fast to save fuel. This is where the lions share of fuel economy lies, if you want to get the last bit of economy then yes, run on one engine. The parasitic loss from dragging the extra prop through the water will cut a bit of economy, but you will save a bit of fuel. I suggest run the boat at less than 7 with both engines, then shut down one while keeping the rpm the same on the running engine, don't try to increase speed back up to 7 on one. It takes a fixed amount of energy (diesel fuel) to move the boat through the water at any given speed. IF you search the forum, dmcb ran his 38 all summer on one engine for economy in the North Channel of Georgian Bay and wrote about it here.

It would help if you included some detail in your signature as to what boat, engines etc so we can be more specific helping out.

James

[zentodd]

Thanks MacPhid - I just figured out how to add the signature. Maybe it’ll come up now. Nope- no signature yet. 1994 3888 with 210 Hino’s and Hurth’s 630A’s

[RDOIII]

It is an interesting question - but I found an interesting - counterintuitive answer. One engine is not necessarily more efficient than two at slow speeds. See my post below

https://www.baylinerownersclub.org/f...ines-at-6-knts

[Uncle_Bob]

Ha, someone just asked me about the fuel cost effects Vancouver to Desolation return. At normal cruising today's fuel price is about 5 cases of wine extra. Of course there's one engine and cheaper wine decisions that can factor into it.

[zentodd]

Now that’s funny - my wife is not going to be happy if I try and reduce the quality of her wine - lol

[Simonsen]

I think a lot of people are taking this year to work on overdue projects, maintenance etc. in hopes that the fuel drops to a more reasonable level at some point (soon). I like to go slow and enjoy the ride, getting there is a lot of the fun for me, sometimes as much as being there, depending on the weather. The summers fuel price will be a doosy for sure, me, I'm thankful we can be on the water even if it's just hanging out on the boat in the marina

[Bobhicks]

It would seem to me that if you are going to run 1 engine and are concerned about uneven wear and tear and tranny not getting lubricated then alternate ever hour/day/etc. to keep the hours the same on each engine. Only thing I can think of that may be a concern is battery charging. Definitely have both engines on when in tight quarters for maneuvering.

[Tex]

ow guys you are happy, i spend more 2 come on the boat, then i use when cruising with it that´s big Mopar engine is damn thursty compare to my 175 Hinos
But yes i would say, always 2 engine and around 6.5 - 7kn is the way...

[smitty477]

You are going to need to be at 5 knots or below to see best 'mileage' or when utilizing a one engine cruise.
At those speeds tides become very important for planning and mileage and in some cases moving faster will be the best plan.