I own a 40 hp 4 stroke Yamaha.Had if for 4 years and have 350 hrs on it
When it was newer when flushing the motor with the rabbit ears the prop would be stationary-Now its a bit older the prop spins
Whould it be that the oil in the gearbox is warm and all the seals are bedded in
Whats yor thoughts ?
Why is it so
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denis barden
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re-tyred
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Re: Why is it so
Hmm, don't know the answer but, my Yamaha 2 stroke 30hp is 16 yo and the prop doesn't spin when flushing. On our coastguard RIB, 4 stroke 140hp brand new this year, it does??
There's nothing . . . absolutely nothing . . . half so much worth doing as simply messing around in boats.
Kenneth Grahame, The Wind in the Willows (River Rat to Mole)
Kenneth Grahame, The Wind in the Willows (River Rat to Mole)
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denis barden
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fishnut
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Re: Why is it so
I find sometimes when water sqirts out the side of the rubber cups and hits the prop causing it to turn
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KeenAds
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Re: Why is it so
There are a few scenarios for this.
First one is the main drive shaft is always spinning while the motor is running so it could be just the force of the oil moving in the gear case that causes the spinning. This is no concern if you are able to stop the prop spinning while in neutral without any effort.
The other thing could be the selection shaft might be ever so slightly out of line and may be just catching the drive gear when in neutral and this can be to a number of things such as just a bit of wear and extra play on the linkage or if the lower unit has been removed recently and slightly put back misaligned.
With the motor off and in neutral does the prop spin freely and no resistance can be felt? If you can feel some resistance this latter scenario is your problem.
Hope this helps.
First one is the main drive shaft is always spinning while the motor is running so it could be just the force of the oil moving in the gear case that causes the spinning. This is no concern if you are able to stop the prop spinning while in neutral without any effort.
The other thing could be the selection shaft might be ever so slightly out of line and may be just catching the drive gear when in neutral and this can be to a number of things such as just a bit of wear and extra play on the linkage or if the lower unit has been removed recently and slightly put back misaligned.
With the motor off and in neutral does the prop spin freely and no resistance can be felt? If you can feel some resistance this latter scenario is your problem.
Hope this helps.
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Nude up
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Re: Why is it so
Just for interest my 200hp yamaha prop 867hrs spins my previous boat 130 hp Yamaha prop spinned as well
Re: Why is it so
Whenever I replace oil seals in gearboxes, etc the new seals "grip" on the shaft somewhat.
The old seals often have no grip at all, so potentially that's what it is. Many lip seals have a spring band that pulls the rubber lip onto the shaft. This might get weaker with time. Plus, in time rubber can lose it's suppleness and grip. Taking that to the extreme have you seen old rubber that is hard and actually cracking.
The old seals often have no grip at all, so potentially that's what it is. Many lip seals have a spring band that pulls the rubber lip onto the shaft. This might get weaker with time. Plus, in time rubber can lose it's suppleness and grip. Taking that to the extreme have you seen old rubber that is hard and actually cracking.