Alpha Gen 2 upper gearcase rebuild,5.0 litre,1.62 ratio.

telstar1

Petty Officer 1st Class
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Jun 20, 2008
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226
I recently had a tooth come off one of the upper gears in the Alpha G2 drive. I noticed a slight change in vibes I guess right when it happened,not far from home dock. I pulled drive and found upper gears bad. Interestingly to me at least,no metal got into lower drive. I suppose because i got on it so fast. I checked this out by repeat flushing with light oil, pretty much nothing ever showed up in lower. The upper was full of metal particles..I did not dissassemble the lower. After rebuild and an hours running I checked again(I put a magnetic plug in top hole during rebuild as well as bottom one). Anyhow all seems good metalwise.Nothing on magnetic plugs.
QUESTION I have is I am noticing a slight gear noise,sort of a light whine or whirring,when Im idling in neutral. It goes away when I put it in gear. Can anyone tell me if this is normal.Its not loud,really only just audible.if you say stand on dock near stern while idling. I ve had Mercruisers for many years and dont think Ive noticed this noise ever before.
I did the rebuild myself,have done a couple before. Did all the shimming and preloading correctly Im pretty darn sure. I actually checked the shimming on old gears before disassembly,they were on spec,and duplicated results with new gears.I did use the shimming tools. Even did a kind of backlash check after reassembly,all seemed good. Wonder if its normal for new gears to do this noise thing?Ive got 2 hours on it now and no change.
 

alldodge

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Mar 8, 2009
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Noticed your post yesterday but left it alone because I figured a Alpha dude would advise, maybe my comment will help get it noticed.

My first thought with your comment about the lower drive and you did not disassemble:
by repeat flushing with light oil

The alpha doesn't use needle bearings like the bravo does so kind of thought your noise should not be from roller bearings. That said, even though you got it quick, if there was metal in the lower section it wouldn't show up from all the flushing.

What weight oil did you flush it with and how was it done, pump in and let drain out?

It doesn't take much of any metal to put a burr or spot on a bearings and or race. Most new gears should not make next to any additional noise. Since it goes away when in gear my thought would be in the upper or lower drive shaft bearings
 

Bondo

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Apr 17, 2002
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What weight oil did you flush it with and how was it done, pump in and let drain out?

Ayuh,.... I wouldn't trust it, even flushin' with diesel fuel,....

For the price of a seal kit, 'n a buck, 'n 1/2, I'd have my Bud up the road tear the lower down, clean, 'n closely inspect the bearin's,......
Dave knows what'll run, 'n what's junk, I bring 'im the parts, 'n his price is always the same,...

As far as the noise,... Donno, some drives are quieter than others,...
Run it til it pukes, 'n the problem spot will show itself, eventually,...
 

telstar1

Petty Officer 1st Class
Joined
Jun 20, 2008
Messages
226
Just found the replies and thanks.I flushed with diesel then light oil,several times. Filled it from bottom,rotated prop a bunch of times,drained. Nothing. Would have thought that the magnetic plug should pick up loose metal no?
 
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