05 Yamaha F90 Lower unit rebuild

bottomfishin

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Jun 7, 2008
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Some observations and a few questions.... In the middle of a lower unit rebuild for my F90 (2005 model), and currently waiting on gears from Yamaha. Had to bore out the section just in front of were the O-ring lies about 3/8" deep just overlapping the pinion hole, due to the gear fragments grinding into the housing. Sleeved it with a stainless steel ring in order to get the shoulder back for the bearing carrier to butt against. Used red loctite and pressed in about .0015". Also notched out the ring for the pinoin hole. After reading the manuel It seemed the only way to correctly check the lash is to almost completly assemble and disassemble, if nessesary. The biggest problem with that is taking out the forward gears' bearing cup and the driveshaft bearing cup. One way around this is if your changing bearings anyway, (I am) is to polish or grind about .002" of of the O.D.'s on the cups so they will slip fit in and out. After this I assembled the old componets back in and checked the lash for sure with an indicator. Funny thing, .012" in one location, .004" with driveshaft rotated 180 degrees. The smaller reading right in front of the broken teeth. Checked driveshaft runout and it is less than .001" So either the gear or housing bore is out of square. Taking out the shim throws it out too much. Can I or should I adjust with using a thin shim to raise pinion gear about .010" ? I have these shims now. Will this affect reverse gears lash too much? According to the book it should need no adjustment. When I began disassembly I noticed very little, if any backlash on the gears, there was oil in the unit and zero water. I think this one got by Yamaha's Q.C. dept. Any thought's or suggestions?
Also....does anyone know the distance from the edge of the driveshaft to the point of measurment on the indicator when checking lash?
 
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