Over-propped good or bad on Transmission?

[Matthew Swasty]

My boat with a pair of QSB5.9-380’s is clearly over-propped and I’m in the process of getting the props reworked so I can hit the proper WOT RPM’s  and be in line with the fuel burn charts.   I know it’s bad for the engines but would my over-propped condition be “beneficial” to the transmissions? (ZF-80A)  I would assume the transmission is not working as hard as the RPM’s are lower at any given vessel speed.   

 

Thanks

Matt

Topic

[Clark Leighs]

For the same HP   higher revs , within the limits of the gear,  are always easier on the gear box.    

I don’t know if you ever drove a standard shift car but think about this.   If you leave the trans in to high a gear on hill climb not only does it lug the engine into possible damage but the pulses from the engine can actually bang the gears in the trans instead of smoothly transferring thrust from one gear tooth to the next.

That same pulsing can momentarily overload the clutch plates causing slippage .    You won’t hear the slipping untill there is enough wear created for them to simply no longer be able to hold lock.

 

My theory anyways.

 

 

[Tony Athens]

Simple answer–Your logic is completely off base–Higher torque into the gears clutch packs at lower rpm’s (your gears weak point) is way harder on it.  

Re-prop your engine correctly

[Author]

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