SX gear chatter?

[crestapre]

I have a joint venture cobra/vp sx twins (1994) that has a new sound this year. When on the trailer and muffs I hear what sounds like gear chatter when I pull back on the throttle (in nuetral). On occation I hear it when in the water again in neutral but the exhaust noise covers a lot so I don't know if this happens all of the time or not. Is this normal? I don’t think that it was there last year (2nd year with the boat)?

This spring I've replaced all orings (upper and lower)and changed the gear oil (Mobil1 75w-90). This is on twin engines and they both have the same noise. I've checked the oil level and it is fine. Would it hurt to try a thicker gear oil like Mobil1 75w-140?

Both drives shift and run great. I really don't want to blow-up these drives. Any ideas?

I talked to the local marina and he didn't really have any idea until he sees it in person but I'm not sure that it really needs to go into the shop.

 

[Don S]

Re: SX gear chatter?

It's hard to answer your question exactly without acutally hearing the noise, that's why your shop wants to hear it.
But my best guess without hearing it is that you are hearing the backlash in the gears in the upper. Once the bearings get broken in and about all the preload is off the bearings and everything turns real easy is when one can expect to hear it. Rough running engine really makes the rattle noticable.
It's pretty much normal and is going to be that way unless the drive is reshimmed and preloads on the bearings reset.
Personally, I wouldn't worry about it. The diesels on the Volvo DP-E and earlier swedish drives make that noise all the time at idle, just because they don't idle as smooth as gas engines. With no ill effects to the drive.
Best to stick with the proper weight gear lube.

 

[crestapre]

Re: SX gear chatter?

Don S. thanks for the advise. It was along the lines of what I was hopeing for.

This is my second year with this boat and I was thinking that all of the new lube in the drive and grease on the bearings and u-joints may be letting the drive move more free.

Is it possible that the shift engagment lever could also need adjustment? When I put the drive back on I left the engagement lever in neutral and adjusted the cable nut into place.

Thanks again

 

[Don S]

Re: SX gear chatter?

When you put the drive back on, you Should check the shift arm on the drive to make sure it's actually going all the way into forward and reverse.
You can do a preliminary check with the engine off, but it's also a good idea to check with the engine idling (Prop Removed) before you put the cover back on.
Just put it in gear and by hand turn the shift are to see if it will go any further, if it does, you need to adjust to get it all the way into gear (Forward and Reverse)