Prop spin at Idle?

**NorCal 98Outback** · 07-10-2011, 09:48 PM

I noticed today that when my engine is in Neutral my prop spin is about one rotation a second. This seems a little fast for being in neutral. Should this worry me? The boat was running on the trailer in my driveway when i noticed this. ZF tranny on my 98 Outback direct drive. Thanks

**phospher** · 07-11-2011, 10:36 AM

They call that dirty neutral. It's caused by warped clutch plates that drag. You'll need to rebuild the transmission.

**lsvboombox** · 07-11-2011, 01:53 PM

seen boats, quads, motorcycles and cars all do this when they are up on a jack...... my Rude '10 225 ho outboard even does it....

**phospher** · 07-12-2011, 11:34 AM

I assure you that your prop should not spin while the boat is in neutral.

**rdlangston13** · 07-13-2011, 08:23 PM

our heavy duty allison transmission on our pumps at work spin in neutral unless they are under a load. these are brand new, never seen one not do it

**phospher** · 07-14-2011, 12:29 PM

Originally Posted by rdlangston13

our heavy duty allison transmission on our pumps at work spin in neutral unless they are under a load. these are brand new, never seen one not do it

Is that the same transmission that is in our boats? Just watch your kids feet under the boat. I'm sure you can call anyone who works on inboard boats and they will tell you it SHOULD NOT spin in neutral. Some trannys do this as you guys described but zf hurth and velvet drives are not one of them.

**rdlangston13** · 07-14-2011, 12:43 PM

i just think that the hydraulic motion of the fluid in the tranny can transfer energy from on spinning component to a non spinning component and cause it to spin slightly without a load. im sure if anyones prop is spinning at idle it is not very fast and could probably be stopped with your hand. also just being in the water could provide enough resistance to stop it from spinning.

**lsvboombox** · 07-14-2011, 01:37 PM

Originally Posted by rdlangston13

i just think that the hydraulic motion of the fluid in the tranny can transfer energy from on spinning component to a non spinning component and cause it to spin slightly without a load. im sure if anyones prop is spinning at idle it is not very fast and could probably be stopped with your hand. also just being in the water could provide enough resistance to stop it from spinning.

+1
in the water if its still spinning i'd maybe be concerned, on the trailer if you cant stop it with your hand then i'd be concerned

**ChrisK** · 07-14-2011, 02:04 PM

What the man with the finger through his eye said.

**cham** · 07-14-2011, 03:50 PM

Originally Posted by lsvboombox

+1
in the water if its still spinning i'd maybe be concerned, on the trailer if you cant stop it with your hand then i'd be concerned

Will you be the official tester for this?

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