1997 merc 50 LU pinion gear only damage

[rickrfa]

I was seeing excessive metal in the LU oil, so pulled it off and opened it up. There is extensive damage to only the drive shaft pinion gear, no damage to fwd/rev gears, bearings, shift dog etc. other than some light score marks on the fwd/rev gears, which just look like typical wear. Motor has about 120hrs total, all fresh water. There were no operational problems with the motor other than the excessive metal in the lube.<br /><br />Questions:<br /><br />1)<br />Do I need to replace forward gear with the pinion, even though it is not significantly damaged ? Would obviously like to save the $210 if possible. Can the fwd/rev gears be resurfaced by a machine shop instead ?<br /><br />2)<br />I have ordered the mercury shop manual (seloc manual has no detail on LU gearcase). Is the shim procedure all that difficult for someone with reasonable mechanical skills, or should I not even attempt it and just have a shop re-assemble the gearcase ?<br /><br />3)<br />Still trying to figure out how the pinion could be so severly damaged, with no affect on the other gears. Is the pinion designed to be a "sacrificial" gear with softer metal ? Anyone seen this type of problem before ? <br /><br />I have a couple photos I can email if anyone wants to take a look.<br /><br />I have searched the forums here, as well as outboards.com, found a lot of good information but no specifics on the gear issue.<br /><br />Thanks for any help/advice

 

[rabidfish]

Re: 1997 merc 50 LU pinion gear only damage

1) If you do not replace the fwd/pinion as a set, you will almost certainly shorten the service life, possibly by a great deal ( read: "may not last more than 20 hours" )<br /><br />2) If you have the Mercury manual, and you're willing to invest in what special tools are needed. Then by all means... try it... If you have any questions/concerns have a Mercury technician check it when you're done. <br /><br />3) There are no "sacrificial" parts in that lower unit. Yes, there has been a few failures... Most that I saw were related to propping,engine rpms,lack of backlash,and impact damage.<br /><br />I am not sure how you got extensive damage, with metal floating around and didn't ruin any bearings, let alone the other gears. Have you actually disassembled it, cleaned it, made a thorough inspection? My guess is the damage may be deeper than you see.

 

[rodbolt]

Re: 1997 merc 50 LU pinion gear only damage

hello<br /> with 120 hours total should be no wear marks anywhere. ofcorse the pinion should not have failed unless its over propped or it something. sometimes there was not enough clearence from the factory. but do clean and inspect everything. I dont think the pinion is avalible seperately. some are and some are not. merc is funny.

 

[rickrfa]

Re: 1997 merc 50 LU pinion gear only damage

Thanks guys. I have the unit dissassembled only to the point of removing the bearing carrier/gear assembly (drive shaft/pinion still in LU, I do not have the proper tool to remove the large retainer nut at the top of driveshaft). Clutch/springs are removed from drive shaft. Cleaned everything as much as possible. fwd gear does have a couple dimples and marks, no chips. reverse gear and everything else looks new. What I can see of the bearings looks very clean, but I realize one cannot tell until they are completely removed.<br /><br />I have decided to take it to a merc repair shop to finish up. Hopefully I will save a little labor cost by doing the initial removal, disassembly and cleanup so they can start right in on final disassembly and rebuild. I guess my feeling is that since the parts are so expensive, I want to make sure it is right. If it was an old "project" motor would probably try myself. <br /><br />From the merc parts site, looks like the major parts cost will be about 205 for the fwd gear, 110 for the pinion, plus misc seals, new water pump etc.<br /><br />What would you expect the labor (in hours) should be to complete final disassembly, inspection and reassembly (foot only, I will reinstall on the motor) ?

 

[rickrfa]

Re: 1997 merc 50 LU pinion gear only damage

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[Greg New Zealand]

Re: 1997 merc 50 LU pinion gear only damage

Always replace the pinion and fwd gear. I know it sounds expensive but I work for a gear manufacturing company and you are definately getting the benefit of mass production - a one off set would be at least 3- 5 times dearer! <br />Set up of these is critical and your decision to get an expert to do the work is a good one - just make sure that your tech knows his stuff!