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My boat is a 2008 Hydra Sport with 2 Yamaha 250's . One has started making a noise like a loose alternator belt under the hood of a car . One dealer says I need the belts checked and possibly replaced . Another tells me it is normal and nothing to worry about . They say it is an engine bushing near the water pump and can wait until fall for lubrication . Does anyone know anything about this ? The motors are under 700 hours . Thanks !
 

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West OC,

The timing belt on the Yamaha F250 won't "slip" like a belt on an automobile. If for some reason it does because of broken teeth on the belt or broken tensioner, you will know it. The F250 is what's described as an interference motor. When the timing is off the valves and piston heads will make contact and result in damage to the valves and/or pistons. You should follow Yamaha's recommendation for inspection and replacement of the timing belt.

The noise you describe is likely from the drive shaft bushing at the bottom of the mid-section (just above the lower unit). If you have ever removed your lower unit for maintenance you guided the drive shaft through it when you re-installed the LU. It's #37 in the diagram below. You should seek out the advice of a Marine Mechanic to verify that is actually what you're describing but it's not an uncommon complaint.

Yamaha F250TUR Upper Casing.jpg
 
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