Prop fell off while under tow?-gctid394677

[Guest]

Was disabled on the water last night. Had to get towed in 5 miles by TowBoatUS. When I got back to my suprise I had no prop! I know it was there as I raised and looked at the outdrive prior to towing.

I suppose the physics all work out...LH prop being pulled thru the water and therefore being pushed back on prop cone while exerting unscrewing directional torque. Has anyone ever heard of this happening before????

[Guest]

that's a first, if your drive was in neutral it shouldn't have happened if it was properly tightened. C'est la vie...

[2850Bounty]

I've not heard of this simply due to being towed.

My bet would be that the spinner was not tight from the get-go.

With your 280 drive, the prop shaft will be internally threaded for the spinner center locking bolt.

Was the locking bolt also tightened?

OK... to avoid the usual confusion regarding the Volvo Penta prop shaft length......, for the 280 prop shaft, you'll need a long spacer/line cutter.... not the short one.

People are led to believe that the propeller hub length dictates the spacer length... it does not.

The 250/270/275 and 280/290/SP prop shafts all net the same shaft spline length when the correct spacer is used.

There....... I just saved you from posting another thread!

See post #13 in this thread for more info.

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[captharv]

If the prop fell off during a tow, you have an issue with the installer. If the prop nut is tight and the keeper was installed, it should not come loose.

I have towed over 200 boats and never had one come loose.

Think about it: It has to withstand a lot of horsepower when you goose the throttle in reverse...

[Guest]

I hear you...but think further...in reverse a self-tightening force would be applied to the spinner/prop cone. Under tow it would be the opposite direction....and only under tow would that force be applied.

I called the towboat captain, he never saw this before either...but all the physics work out.

Bottome line: locktite the bolt and crank the spinner home...is there anything else I can do to not drop $500-worth of parts to the bottom of Lake Erie again?

[2850Bounty]

Silver Fox wrote:
I hear you... but think further...

• 1 wrote:
• in reverse a self-tightening force would be applied to the spinner/prop cone. Under tow it would be the opposite direction....and only under tow would that force be applied.
• Bottome line: locktite the bolt and crank the spinner home... is there anything else I can do to not drop $500-worth of parts to the bottom of Lake Erie again?

• 1 wrote:
• This depends on which hand prop you are using. You mentioned that you were using a LH prop.
  
  A LH prop under power would tend to tighten the spinner.
  
  A LH prop under tow would also tend to tighten the spinner.
  
  Reversing a LH prop may loosen a spinner that was not locked.
• No need to use loc-tite, IMO.
  
  With a spinner in place, you may not be able to apply heat in the event that heat was necessary to release the bolt later on.
  
  The OEM bolt has a locking "pill" inserted in the threads.
  
  Tighten the spinner first, then gently lock the center bolt.
  
  If using the short hub prop and the SS tab washer, tighten the spinner, then fold several tabs into the castellated areas.

[Guest]

2850Bounty wrote:

• 1 wrote:
• This depends on which hand prop you are using. You mentioned that you were using a LH prop.
  
  A LH prop under power would tend to tighten the spinner.
  
  A LH prop under tow would also tend to tighten the spinner.
  
  Reversing a LH prop may loosen a spinner that was not locked.

No it wouldn't! LH prop looking from aft POV would spin anti-clockwise going forward. Under power it would be pushing forward against the outdrive making the boat move forward. Under tow it would still be spinning anti-clockwise but would be pushed backward against the spinner/cone due to being dragged thru the water. From the aft POV that would put lefty-loosey spin on the spinner/cone. If it were at all loose, adios prop!

Reversing a LH prop would cause it to spin clockwise from aft POV. It would also be exerting a pushing force backward onto the spinner/com. But the force and spin would be in a self-tightening manner against the spinner/cone.

[2850Bounty]

Ah then.... I have a question for you:

Why would a LH propeller (that turns CCW when viewed from AFT... just as we view engine rotation), somehow slip on the splined shaft so that it could work against the spinner?



The LH prop roates CCW while under engine thrust.

When the boat is being towed, similar hydro action occurs.

But instead of the propeller supplying the thrust, the prop is now being turned by the same direction of water force passing over the blades.

I agree, the slack would be taken up in the oposite direction.

But somehow the prop would need to slip on the splined shaft so that it could work against the spinner.

If you were in mid air in a small aircraft, and if the engine was to die, and if you went into a steep dive, would the air force over the propeller somehow miraculously cause the prop to remove the prop nut?

I know..... that's a bit of a stretch, isn't it?

.

[Guest]

Ah yes, the splines would prevent that...dammit

Well then I figure my 28 y.o. boat is so finely tuned that when I stop forward throttle, the shaft stops so crisply that the cone's rotational inertia (being so great because my boat is so fast) keeps the cone spinning and it spun its way off. That is my $500 story and I'm sticking to it.

Airplane: only if diving tail first...and that just don't happen.

[2850Bounty]

You're good sport! :coo-

Look on e-Bay...., you may be able to find replacements at a fairly good price.

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