Running on one engine

[wshelton]

I think I have read info regarding my question here, however want to double check.
I have twin DD 671Ns and Allison M20 gears I believe. I am going on about a 80 mile trip with a dock buddy that runs very slow. About 8 Knots at best. I have no problem running at this speed but would like to run on one engine to save $$$$. My boat is easy to maneuver on a single as I grew up on a single anyway.

Do I need to lock down the shaft on the engine not in use for this time that that engine is not running? If not I assume I leave it in neutral or should it be in forward gear assuming I go straight and not drink to much going his slow.

Do not want to burn up a reverse gear.

Thanks,
Will

 

[GJH]

Yes you have to lock it down physically if the engine isn't on. But as we have discussed here before,the savings are minimal-to-none running 8 knots on one engine vs. two. Just light them both up and then run up at 90% of WOT at the end of the day for 20 minutes.

 

[SeaEric]

+1. A pair of 671 N's won't burn that much at slow cruise. Why take a chance?

 

[34Hatt]

Oh Boy here we go again!

 

[jim rosenthal]

This has been discussed endlessly and you can find it through the search function. Bottom line? Don't do it.

 

[saltshaker]

A 671N burns 2gph @ 1000rpm and 3gph @ 1200rpm. This applies to all recreational marine rated 671N's including the 310HP J&T's. I'm sure 1000rpm will push you 8kts or better so your fuel burn will be 4gph plus the generator. If you know your hull speed and the rated HP of your engines you can determine what rpm will be needed to achieve that and then see what your fuel burn is. If you can get better than 2mpg without having to deal with locking the prop why even consider doing it? This way you have the use of both engines for tight quarter maneuvering and the ability to get up and go if necessary.

 

[Freeebird]

I think I have read info regarding my question here, however want to double check.
I have twin DD 671Ns and Allison M20 gears I believe. I am going on about a 80 mile trip with a dock buddy that runs very slow. About 8 Knots at best. I have no problem running at this speed but would like to run on one engine to save $$$$. My boat is easy to maneuver on a single as I grew up on a single anyway.

Do I need to lock down the shaft on the engine not in use for this time that that engine is not running? If not I assume I leave it in neutral or should it be in forward gear assuming I go straight and not drink to much going his slow.

Do not want to burn up a reverse gear.

Thanks,
Will

It could be argued I'm the single-engine king of this place, but why in the world would you worry about running on one engine if you're only running 80 miles?

As for your boat being easy to maneuver on one engine, I'm guessing the single you grew up with wasn't half of a pair. Not trying to beat up on you, but have you actually tried docking your boat using only one engine?

My advice?... be happy both your engines run and have a nice trip.

 

[Freeebird]

A 671N burns 2gph @ 1000rpm and 3gph @ 1200rpm. This applies to all recreational marine rated 671N's including the 310HP J&T's. I'm sure 1000rpm will push you 8kts or better so your fuel burn will be 4gph plus the generator. If you know your hull speed and the rated HP of your engines you can determine what rpm will be needed to achieve that and then see what your fuel burn is. If you can get better than 2mpg without having to deal with locking the prop why even consider doing it? This way you have the use of both engines for tight quarter maneuvering and the ability to get up and go if necessary.

Another option would be to idle the engine that's not being used for propulsion. That would protect the transmission and save $1.98 on fuel... maybe.

 

[wshelton]

I truly appreciate ALL the advice on apparently such a stupid question. Obviously I would not consider docking on a single although I have done it before albeit the judicious use of the rudder and proper torquing was a necessity, I accomplished this without any concerns.

I will certainly be more practical in seeking advice in the future.
I guess I was considering engine hours and All the other issues that run through the engine, and not the fuel burn.
Why own one if you have to worry about the cost to fuel. At least in all my years this has not kept me from running year round.

Thanks Again,
Will

 

[labrador]

You could always do what Randy did, remove the prop before leaving then get your scuba gear out and just pop it back on when you reach your destination. Lets see, remove prop, 1hr lost prop nut 2hrs to get another, go 80 miles, try to reinstall prop, drop prop in 80' of water (%^$#@( lose $2500.00 for prop, forgetabboutt it!!!!!!!!! just pay the $2.00