freewheel tranny?

[Carolyn Phillip]

Hello dear fellow cruisers!
Does anyone know if allowing our Twin Disc transmission to freewheel without the motor (GM871) running will damage it? (On the tugs with1271's we always locked the shafts because the trannies needed the engines running to circulate oil). We would surely appreciate advice on this, thanks!
Carolyn Phillip

 

[Comodave]

Do you have the owners manual? I would get one and use that as the guide, not what anyone here thinks unless they have the manual.

 

[Ken E.]

Like Dave said, the owners manual will tell you which Twin Disc models can be freewheeled. Most can. You can get a pdf file of your owners manual at the Twin Disc website.

 

[tiltrider1]

If you fill the oil level to the recommended line on your dip stick then you should lock the shaft to prevent damage. If you fill the transmissions full then freewheeling is ok. There is always an exception so follow the above advice and make sure your transmission is approved for free wheeling.

 

[mahal]

Carolyn, if it turns out that your tranny can be freewheeled, keep an eye on the temperature of the stuffing box. I had to shut down one of my engines a couple weeks ago - I let it freewheel and my stuffing box got very hot measuring 250 deg F.

BTW, how did you lock the shaft on your previous boat?

 

[Carolyn Phillip]

Carolyn, if it turns out that your tranny can be freewheeled, keep an eye on the temperature of the stuffing box. I had to shut down one of my engines a couple weeks ago - I let it freewheel and my stuffing box got very hot measuring 250 deg F.

BTW, how did you lock the shaft on your previous boat?

On one sailboat I sailed years on, the owner locked sailboat shaft on long ocean trips with big vicegrips. Now we never bother with these of ours and had no problems while sailing with engines off and props freewheeling (with the Yanmar 2 cyl and 3 cyl engines on our sailboats).

 

[Carolyn Phillip]

Thank you all so much for your input/replies responsive and kind fellow Forum members. As you recommended, I did download and read the manual, and yes it did give model #'s for the TWIN DISC transmissions that need the shafts stopped from "freewheeling" to prevent overheating, and our MG506-1 was not included with those recommended to be stopped. I will phone the Twin Disc Company and ask their Techies/Engineers as well, just to double check, and watch the transmission's temperature while freewheeling the prop of the one engine not in use while underway. We will only be going 5 Kn while towing the sailboat, and so far the trannies Temps have not exceeded about 130 degrees F. We only have been using one of the big almost 400HP diesels to save fuel (>$10 gal where we got last fill in outisland Bahamas). We longtime old sailboaters and newbies to big double engined powerboats are not used to such fuel consumption!

 

[jgwinks]

There's been other threads on this, but I'm not sure you'd save anything by shutting down one engine. It takes x horsepower to move a boat at a given speed, and of you're doing it on one engine that engine is working twice as hard as two would be. Add to that dragging the dead prop, whether locked or free wheeling, through the water which is a lot more drag than you'd think. That's why a lot of sailboats have folding or feathering props, it makes a big difference in sailing speed.