Stop Freewheeling Prop?

W

Warren

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I have often wondered how I would stop one prop from freewheeling if I had to run to port on the other engine. Will putting the engine in reverse keep the disabled engine's shaft from rotating? Someone suggested locking large Vicegrips onto the shaft and tying them in place - but shaft access is negligible. Doing that under a hot engine in a seaway could be a challenge too.. Any other suggestions out there?
Warren
 
take a line and slip bitter end through loop, put new loop over hub where shaft comes trough trani. Pull snug on it and put other motor in gear, slowly feed line as it wraps the hub as it will begin to move when the boat picks up a couple of idle knots, if not idle up a bit, when you have a good amount of line spun, stop boat, tug to snug and tie off to the motor mount, put in gear and go home....slowly.
 
I don't know about your 40, but my 340 has a cross feed to cool/lubricate the shaft seal on either side as long as one engine is running. For everyone, the way you can tell is that there will be an extra line running from the Strong seal, over the stringer, across the bilge, over the other stringer, and into the other Strong seal. On my boat, it's a thin (3/8" or so), black tube. Once you see one, you can spot them in a second just by looking down into the ER.

I believe that the way they work is they simply allow water to flow freely from one side to the other. Whichever side has more pressure will force water to the other side.
 
I've got ZF transmissions and the owner guide states that freewheeling will not damage the transmissions. There is no need to tie them off.
 
Damage to the transmission depends entirely upon what transmission you happen to have, and whether or not the transmission is in gear or stuck in gear. Some clutches are pressure activated and don't engage unless the engine is running; those that do partially engage will have clutch wear if they are towed or are towed in gear with the prop windmilling.

On Hurth 800IV, ZF-80IV or -85IV, you can also slip a 2" open end wrench or a 24" adjustible wrench or even a pipe wrench over the shaft nut then pull the wrench over to the stringer and tie it off to secure the shaft from turning.
 
Last edited:
sbw1 said:
I've got ZF transmissions and the owner guide states that freewheeling will not damage the transmissions. There is no need to tie them off.
Click to expand...

Correct me if I'm reading this wrong, but that covers the transmissions, not the shaft seals.
 
Yes. You are putting a finer point on the discussion. The seals are a different matter. Mine cool with a cross over. The owner manual for the trannys also says that in gear or out of gear is not an issue with freewheeling. Your question really underscores the importance of knowing what you have and how you need to operate your specific equipment. There is no substitute for reading your manuals.
 
All good suggestions, thanks. From the comments it would seem that you advocate leaving the trans in neutral and tying off the shaft. The question was really prompted by a concern about damaging a shaft seal which are not cross cooled on this boat.

However, I was also wondering if water could siphon through the exhaust and into the engine if the operational engine were to move the boat ahead at, say, 5-10 kn. Is that also a concern?
Warren
 
Warren said:
All good suggestions, thanks. From the comments it would seem that you advocate leaving the trans in neutral and tying off the shaft. The question was really prompted by a concern about damaging a shaft seal which are not cross cooled on this boat.

However, I was also wondering if water could siphon through the exhaust and into the engine if the operational engine were to move the boat ahead at, say, 5-10 kn. Is that also a concern?
Warren
Click to expand...

Wow! Another Monty Python sketch. Not really. Just kidding. I don't think that's an issue, but, I will allow the truly blessed diesel owners, one of which I hope to be some day, pass the official word on this one. Gary? Frank? Others?
 
Warren,

The cross-over cooling water is going to seek the lowest resistance path out and that is thru the seal on the dead engine side, not back up and into the exhaust.

If the boat does not have cross-over cooling, the venturi actioin of the water over the aft end of the shaft tube is going to create a vacuum on the cooling system at the Strong seal so water is going to be pulled out of the engine, not back uphill into it.
 
Thanks for the technical explanation - clear as mud Frank but, anyway, to summarize:

With a disabled engine one should: (a) leave the trans in neutral and (b) tie off the shaft to prevent freewheeling. No need to shut off engine water inlet.

And I'm good to run home slowly on one engine.. End of story. Have I got it?
Warren
 
I've read the owners manuals and all the suggestions in this and other threads on numerous occasions. I made the decision, a few years ago, that if I need to travel a 'good' distance on one motor, that I would simply tie off the dead shaft and close my seacock. Why? Well, two reasons. First...when the time arrises, I've just had a bad experience with losing a motor and I don't want to make it any worse by taking any chances. Second.....you may lose both motors one day from a 'common' cause and need to get towed home....then what....well, then you need to tie off both shafts and you'll already have the neccessary 'stuff' on board and the know how to git 'er done....
 
Sound advice Dom. Guess that pretty much completes the thread.. thanks for the input!
Warren
 
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