Tapping in F25 Gear Case

[charvett2]

I just bought a used 2001 Yamaha F25 electric start, and started it on muffs for the first time today. I'm a car guy and very familiar with engines, but a novice with outboards. Everything seems good with the motor except an occasional tapp in the mid section. It sounds similar to the noise of putting it into gear.<br /><br />Doesn't sound like anything too serious, but not sure. In car terms it almost sounds like the gear synchroids are a bit off. <br /><br />Is this normal behavior for an engine of this age?<br /><br />Not sure if I'm making any sense here.<br /><br />Thanks for any help!

 

[WillyBWright]

Re: Tapping in F25 Gear Case

If you put it into gear (without the motor running) you'll notice that the prop will twist back-and-forth at least 90 degrees. That's the noise you're hearing ... the shifter cogs banging on the gear cogs. It probably won't happen in water when the prop isn't nearly so free to rattle about.

 

[rodbolt]

Re: Tapping in F25 Gear Case

that unit has no synchronizers, its a mechanical slam shift, its possible the shift linkage is out of adjustment. its alos possible the noise is telegraphing down that hollow housing.<br />with the engine off and in nutral push and pull on the propshaft while rotating it. if you can feel the clucth tapping the gear dogs its out of adjustment.<br />or something is broke.

 

[WillyBWright]

Re: Tapping in F25 Gear Case

Or the prop is loose. A lot of people put the nuts on finger-tight. It needs to be snug. Not lugnut tight, just good and snug.

 

[charvett2]

Re: Tapping in F25 Gear Case

Thanks for the responses. It's much appreciated! <br /><br />The noise doesn't sound like anything too serious, almost like it needs a slight adjustment as mentioned. <br /><br />When it's in neutral the tap occurs about every 30 seconds, but in gear about once every couple minutes. Sound seems to be coming from the midsection just under the plastic cover.<br /><br />If it needs adjustment, will it hurt to take it out for one trip? I've got a trip coming up and it runs so well I hate to tear anything down so close to go time. <br /><br />I'll check that the props snug just to be sure. But I suspect it's OK.<br /><br />Thanks again!

 

[rodbolt]

Re: Tapping in F25 Gear Case

if it taps in gear its either incredibly out of adjustment and most likly suffers from shift clucth damage or the noise is not in the gearcase.<br /> listen to it with the prop loaded in the water and see if its still there, an unloaded propshaft/driveshaft will make odd noises that are perfectly normal sometimes.<br />at an idle unloaded the shafts are constantly accelerating the deaccelerating with crankshaft pulses.