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Lower unit excessive backlash

V

vroomZOOM

Regular Contributor
Hello

When I went boating last year I heard a whining noise from the lower unit as I brought down the throttle to about 4000 rpm. my seloc manual says it is excessive backlash causing the problem. I took the lower drive apart and the driveshaft has play up and down (maybe 1mm). what part is worn down and where do I get it? The driveshaft has to go down more, so it cant be the top bearing. I saw some kinda spacer, so I am thinking its that. how do I get it out though?

Thanks
 
There is more to it than the driveshaft moving " up and down "--------Have you looked at the gear teeth and bearings , yes or no?-----A shop would use shimming tools to put the gears in the correct position.-----And on most motors with gears shimmed correctly there is up and down movement of the driveshaft.
 
Took the whole thing apart... used gear marking compound and the gears seem to be too far apart - not horrible, but it would be better if they were a little closer together. bearings are smooth, or so said the pro mechanic, and I never really had any issues until I must have made them when I replaced the seals and o rings - the whine came in then. the gears don't seem to be too badly worn either. also, will the crankshaft prevent the driveshaft from creeping up? the problem is only when I coast, so since the gears are semi spiraled, when the tourqe is coming from the engine, will it pull the pinion gear down into alignment? there is no bearing to keep it down, only one to keep it up, so I am pretty sure that that is the case. when I coast the tourqe is coming from the prop and its pushing the pinion gear up and creating the excessive backlash - anyways, this is my hypothesis
 
Did you forget to mention what motor this is ???----Is there a spring loaded pin on the end of the driveshaft?
 
When the torque comes from the engine the pinion is PUSHED UP on most motors.----Don't think yours is any different.
 
Hmmm... seems pretty funny to have the pinion pushed up on the motor - why have a bearing then to prevent the driveshaft from going down, and no bearing to prevent it from going up? I don't think Yamaha engineers are that stupid. as for the preload pin, only 90 and up engines have them as far as I know - mine is an 89' 50ELF. anyways, I took out some shim material and after turning the driveshaft while pushing down I got a great gear pattern.
 
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