Whine From the Outdrive

[hsvengr]

2006 Mariah SX-19, 4.3L Mercruiser V6, Alpha I outdrive:
There's a fairly loud whine (not a grinding sound) coming from the outdrive. The lower unit should be OK -- it is an SEI replacement put on last year. My mechanic thinks it could be coming from the upper unit of the outdrive. Do you have any thoughts about what could be causing this whine?
Thanks,
hsvengr
P.S. The noise only occurs when under load (in the water, moving forward). You don't hear it with the engine running, in gear, on the trailer, with muffs of course.

 

[Don S]

Re: Whine From the Outdrive

What happened to the old lower? Did the noise start immediately after installing the new lower?

 

[hsvengr]

Re: Whine From the Outdrive

Struck a submerged object -- log, I suppose. Bent the prop severely, broke the skeg off and part of the anti-cavitation plate, broke the gimbal casting. Replaced with new Mercruiser gimbal casting, SEI lower unit. Was not aware of the whine before the crash. Heard the whine immediately after the new lower unit was put on and attributed it to break in noise -- a whine that should lessen after break in is complete. Have about 15-20 hours on the new lower unit and it still has a loud whine. But my mechanic, using a listening stick, thinks the noise is not from the lower, but is from the upper unit.

 

[Don S]

Re: Whine From the Outdrive

With that much of a hit, it's very possible something happened in the upper. Was it disassembled and inspected after the accident?

 

[hsvengr]

Re: Whine From the Outdrive

Not disassembled, but the mechanic did replace the gimbal bearing and examine some other part (whatever else you can check thru a port?) and said it looked lubricated and OK.

 

[Fordiesel69]

Re: Whine From the Outdrive

Pull the top cap off the upper unit (4 bolts and have a look) I bet the bearings are toast.

 

[Kaplooi]

Re: Whine From the Outdrive

A persistent, loud whine sounds like gears may be grinding. Bad bearings tend to make more of a growling sound in my experience, but that doesn't mean you could have damaged bearings as well as gears being out of adjustment. You should know that the driven gear's position in the upper unit is shimmed to a tolerance of 0.025in in order to mate up properly with the teeth on the u-joint drive shaft which is also shimmed to that tolerance in order to exactly center the drive shaft in the drive shaft housing. If you're saying the lower unit sustained a hit hard enough to break off the skeg and part of the cavitation plate as well as crack the gimbal ring is it so hard to believe the drive shafts in the upper unit may have moved more than 2 hundredths of an inch as a result? The whine is telling you that at best you're spinning bad bearings and at worst you're doing damage to your gears so you (or someone) should get in there and fully inspect the upper unit gears, bearings and shims at a minimum.

 

[hsvengr]

Re: Whine From the Outdrive

Thank you, Fordiesel69 and Kaplooi, for those suggestions. I will pass them on to my mechanic. Perhaps the gears were banged around by the impact to the lower unit and knocked out of alignment. Makes sense to me and sounds like it could be the source of the whine.