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-   -   One prop spins in high current? (https://www.trawlerforum.com/forums/s6/one-prop-spins-high-current-50992.html)

RonR 05-26-2020 02:22 PM

One prop spins in high current?
 
Recently we were anchored out in a very high current area. I could hear a noise like something was moving but could not figure out what I had left on. Opened up the hatches and noticed one shaft was turning but the other was not. Is this normal? Each transmission was in neutral, engines off. It made no change when I put the spinning one in drive, it kept slowly turning in the current.

bayview 05-26-2020 03:51 PM

That is not unusual. One stuffing box may be a bit tighter than the other. Since it only happened at an anchorage not your dock I would not worry abut it.

Comodave 05-26-2020 03:55 PM

We had a 500 rain/flood last week. Our river was running at 6.8 mph. I thought that my props might spin but they werenít.

Pete Meisinger 05-26-2020 04:02 PM

I guess I don't see a problem with it. I'm sure it can not generate any heat at the stuffing box which would be the only worry.

If it did this for days or weeks, like at a river dock I guess I would want to stop it with a clamp or rope or something but for a day or so I don't think it can damage anything

pete

Comodave 05-26-2020 04:05 PM

Some transmissions donít like freewheeling for very long. That would be the main concern for me. Look in the manual and see if yours are able to freewheel or not.

HopCar 05-26-2020 04:11 PM

I think I would have stopped it. Anything moving makes wear and it would be annoying to listen to. Not really a big deal.

Insequent 05-26-2020 04:31 PM

I've had props spin at anchor, probably about 3+ kn of current. And it was relatively slow turning. It was also only a short period when tidal flow at at is highest, not right through the night.

For the OP I'd worry about why the other one was not spinning. Shaft bent? Out of alignment somewhere? Stuffing box way too tight?

Stout 05-26-2020 05:58 PM

We had the same issue this weekend for the first time on the Columbia River. The spring melt is on and we were just below the Bonneville dam. The river was up about 8 ft and when we drifted in the main channel our speed was about 6.5kts SOG. The PYI shaft seal started squeaking where we moored and was obnoxious. I had to use a rope to stop it and then put a wrench on the shaft flange to stop the rotation. I put a post it over the start button to remind myself to remove the wrench :angel:

High Wire 05-26-2020 06:06 PM

My single spins at anything above 2 knots. Aft a few hours I put my hands on the BW 71 trans. There was no warmth at all.

RonR 05-27-2020 09:39 AM

Thank you, first time I have experienced this. We normally do not sit in a high current area, so it was a first for us. As for one spinning and one not... I have no idea why.

Larry M 05-27-2020 11:15 AM

When we were PNW based, we had the prop spin a few times when we were side tied to a dock in La Conner, WA. It only happened once or twice and at maximum flood or ebb tide in the slough.

As far as why one spins and the other doesn’t, my guess would be the tightness of the stuffing boxes and possibly even the alignment with the cultless bearings. I wouldn’t worry about it, but that’s me.

kapnd 05-31-2020 03:08 PM

I’m pretty deaf, so such things seldom register with me, but one night On a wild anchorage I had some definitely landlubber guests sleep over, some on the deck.
In the morning, I noticed a line over the gunnel, asked about it, and was told that the rumbling of the cutless bearing made sleep impossible, so these lubbers came up with a surprisingly workable solution, without even getting wet!

Comodave 05-31-2020 04:25 PM

Quote:

Originally Posted by kapnd (Post 884557)
Iím pretty deaf, so such things seldom register with me, but one night On a wild anchorage I had some definitely landlubber guests sleep over, some on the deck.
In the morning, I noticed a line over the gunnel, asked about it, and was told that the rumbling of the cutless bearing made sleep impossible, so these lubbers came up with a surprisingly workable solution, without even getting wet!

Did they get wet getting the line out of the prop?

AKDoug 05-31-2020 08:10 PM

A dripless gland will not like to be spun without water pressure, conventional packing in the gland doesn't care whether it spins or not. It will drip and cause no issues. This issue came up in a question about towing, and the answer was the same. If being towed and using a dripless you need to lock the shaft while being towed. It's also a good idea to close the valve for your raw water to the engine to keep water from being forced into the system (exhaust) under tow if you have a forward facing strainer.

FF 06-01-2020 05:49 AM

"I put a post it over the start button to remind myself to remove the wrench"


Plan B is to hang the start key on the wench

rslifkin 06-01-2020 06:01 AM

My usual method is to trip the ignition breaker for an engine if it's not in a safe condition to be started. Then you can turn the key all you want and it won't crank or start, as there's no power to the ignition switch.

oscar 06-01-2020 07:29 AM

Quote:

Originally Posted by Comodave (Post 882935)
Some transmissions donít like freewheeling for very long. That would be the main concern for me. Look in the manual and see if yours are able to freewheel or not.

^^^^^ This.

Ski in NC 06-01-2020 09:01 AM

If you are going to dog the shaft to prevent windmilling, use a zip-tie. That way if you forget and crank the engine it just breaks the zip tie.

adornato 06-08-2020 01:58 PM

on our J105 sailboat, with a yanmar 2GM20F engine, we put the transmission in reverse after we shut down the engine and are sailing 5-7kts to prevent the prop from "windmilling"
so does everyone else on sailboats.. why not just put your trawler in gear and let the engine compression keep the prop from spinning?

rslifkin 06-08-2020 02:01 PM

Quote:

Originally Posted by adornato (Post 887440)
on our J105 sailboat, with a yanmar 2GM20F engine, we put the transmission in reverse after we shut down the engine and are sailing 5-7kts to prevent the prop from "windmilling"
so does everyone else on sailboats.. why not just put your trawler in gear and let the engine compression keep the prop from spinning?

Most of us have hydraulically engaged transmissions rather than mechanical like many small sailboat auxiliaries. So if the engine isn't running, moving the shifter does nothing. Without the trans input shaft spinning, the pump isn't spinning, so there's no pressure to engage the clutch packs.


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