# Yamaha F40 prop problems.



## Brett (Jul 16, 2008)

Check for fuel system blockage. I don't think it's the prop.
I'd be looking for a dirty fuel filter or an air leak restricting fuel flow.


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## crl.wms (May 5, 2011)

Something is definitely wrong.  An easy check is on GPS speed.  If the RPMs are correct with your gear ratio and RPM you would be running 21-23 mph.  If you are running faster than that, then the tach may be set for 4 cylinders instead of 3 cylinders.  Alternatively, that prop should deliver 31 - 34 MPH if the boat+engine can deliver that speed at target 5500 RPM.
As Brett noted, if the engine isn't getting fuel, is sucking air or the throttle linkage is binding all could be a problem.  But it is easier these days with a handheld GPS to check speed first.


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