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Author Topic:   Propeller HELP!!!
Duncan posted 05-10-2001 08:35 PM ET (US)   Profile for Duncan   Send Email to Duncan  
Last night whilst ripping down the Hudson from the Geo Washinton Bridge to scenic Wehawken in my 13', I "spun" a prop. Never experienced this before. Going fullbore, the engine revved beyond redline and (most) forward progress ceased.
I was able to limp back to the launch at no better than trolling speed...anything faster and it'd just rev and not speed up.
Upon investigation tonight, I found that the core (female) part of the hub of the prop is apparently seated in rubber (in leiu of an old-fashioned shear pin???) and when I grab the prop and try to turn it with the motor in gear I can make the core slip. What gives? Can this be repaired? Or do I just replace the prop?
Motor is a very tired 1977 Johnson 35 and the prop that's on there is a 10 1/2 x 11 versus the 10x13 or 10x15 that would normally be used. Was this done to give the old motor a break? Can I go to a 13 or 15 pitch and still get on plane?
Tom W Clark posted 05-10-2001 08:43 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Duncan, I believe any prop shop should be able to replace the rubber hub in your prop. As to the correct pitch, if your 11" prop puts the motor beyond the WOT RPM range, then you need a taller prop, propably the 13". If the 11" puts it in the correct WOT range then leave it.
lhg posted 05-10-2001 09:58 PM ET (US)     Profile for lhg    
I had a Mercury Laser prop "spin" the rubber hub on me just recently. In all my years of boating (34) never experienced this before. Initially, I thought the gearcase let go. Cost me $60 to have a new rubber mount installed in the propeller.

Getting a prop off after it "spins" is not easy, at least it wasn't on my 200. Normally the prop blade serves as the resistance to loosen the prop nut. With a "spun" hub, this doesn't work. The mechanics knew that they had to, instead, wedge the engine flywheel to free up the nut and prevent the prop shaft from turning.

They figured that sometime in the props' life, although it was perfect with no dings, I must have hit something. Then, when I accelerated out of no-wake zone, it let loose. It was a 12 year old prop. The scarry thing is that this can happen to anybody at anytime, without warning. As Duncan says, if it does, you will still get back in, but need to go slow to keep from loading the prop.

In Mercury's new props, as of 1999, this can't happen, as the friction rubber system has been eliminated, in lieu of a splined plastic insert that will shear totally, but not gradually wear and then spin out.

blackdog posted 05-11-2001 09:08 AM ET (US)     Profile for blackdog  Send Email to blackdog     
Can you still get back into port with the new Merc Plastic hub? or does it just spin.


Duncan posted 05-11-2001 01:01 PM ET (US)     Profile for Duncan  Send Email to Duncan     
Thanks for the help. I bought a new one. Anyone know if I can repair the old one (with some sort of adhesive or marine tex) for use as a spare?
bigz posted 05-11-2001 01:31 PM ET (US)     Profile for bigz    
Sorry Duncan no you will have to get the rubber hub replaced. Hey in reality small price to pay for a spare prop now don't yeah know!

We carry a spare prop/s on all our 27 Whaler boats, a spun prop/s on those will not work all to well though they will still plane on one engine so maybe I'm to cautious. Then again on the big guys just might loose both at once or you might be a long way form where you have to go or yeah never know whether it will be the right or left hand prop,--- chuckle glad I carry spares, know as soon as I don't bang I loose one or both ---

As the saying goes no prop no go go.

Just had a 9.5 Johnson vintage '76 bubble spin out last Fall, original prop, throw away nothing much on the old little ones. She did get me back to the dock though real slow like. A local old time OMC dealer had an original NOS got it for all of $45 if I recall --- she purrs real nice like now! --

Tom W Clark posted 05-11-2001 11:19 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

Here's a question for you. If you have a twin outboard boat with counter rotating props and you carry only one spare, let's say it's a right hand, and the motor with the left hand gets its prop damaged, could you use the right hand spare on that motor and simply run the motor in reverse? Would that damage the gearcase? Could you do it at slow speed?

jimh posted 05-11-2001 11:32 PM ET (US)     Profile for jimh  Send Email to jimh     
This is a corollary question to Tom Clark's:

On "counter rotating" outboard engines, is it the power heads that are running in the opposite direction or is it the gearcases?


lhg posted 05-12-2001 02:34 PM ET (US)     Profile for lhg    
Tom - as far as I know, you can't get much power running a counter rotating engine in reverse. So what you are proposing won't work, I DON'T THINK. (Never tried it and am afraid to!) Generally, with CR engines,
you would need to carry two spares, and both should be 4" lower in pitch, for the situation where you have to do some serious running on one engine.

But I don't bother, as that is one of the reasons for twin engines. On a couple of trips to the Bahamas, I carried a CR prop as a spare, since those are often the hard ones to replace locally, anywhere.

Jim - it's the gearcases that provide conunter rotation. And also, CR engines require a differently configured shift control. As an example, the same dual engine control box on my 18 will not work on the 25, and visa versa.

Tom W Clark posted 05-12-2001 06:09 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Somebody correct me if I'm wrong, but I think the OMC counter rotating motors (or at least some of them) actually have the power head going in the other direction. I know this is the case with some inboards and I/O's.
Peter posted 05-12-2001 11:27 PM ET (US)     Profile for Peter  Send Email to Peter     

I believe that the 10 1/2 x 11 prop was standard issue on the 1977 Johnson/Evinrude 35. That's the way mine came way back then. Yours may be the original prop. I found that the 10 1/2 x 11 was useful for water skiing. Used a 10 x 13 SST for speed and better "traction" but it was not great for water skiing. I think that the 10 x 15 would be too much prop for the 13'.

Duncan posted 05-16-2001 10:42 PM ET (US)     Profile for Duncan  Send Email to Duncan     
THanks all for your input.
Peter, Thanks for the info. I tried a 10 x 13 but it took 30 seconds for the old bugger to get on plane. The guy I bought it from let me switch it for a 10.5 x 11. Fine now.
You may be may have been original. The Michigan Wheel replacement prop I bought is a piece of junk compared with the old one.
Peter posted 05-17-2001 07:32 AM ET (US)     Profile for Peter  Send Email to Peter     

Sounds like your old 35 is tired. My recollection is that with one or two persons the 10 x 13 it would get up on a plane in a reasonably short time, although not as fast as with the 10.5 x 11.

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