Correct way to rebuild/re-shim mercury 110 9.8hp lower unit

[Chevyls6]

Alright boys ive got the parts on order to fix my merc lower unit after finding water in the oil. Ive got all new bearings and the updated stainless driveshaft and shift shaft coming in.

Will i need to change the shimming or can i reuse the stock setup? Im keeping the original housing and gears since they are in fine shape.

When doing outboard lower units does the contact pattern get checked with marking compound like an auto differential or is backlash the only important measurement?

 

[Faztbullet]

Will need to reshin as bearing/race may be tad over/under. Will need to set forward /pinion preload and pinion height and backlash along with water pump base ..

 

[racerone]

Proper tooth contact is most important !!

 

[Chevyls6]

When i took it apart there weren't any shims under the water pump only under the upper driveshaft bearing.

It does however mention shimming that part in the manual.

I can see the outline of the original wear pattern on the gearset so ill try to match the contact pattern to that.

 

[Chevyls6]

Ok i got the shim kits ordered. Thank god i could find them.

$20 for a couple tiny shims, ouch lol

 

[MercGuy]

I don't claim to be an expert on this topic, but years ago I was taught that the the original shims should be fine for a lower unit rebuild. The logic was that any variations that require shims are due to the original machining of the lower unit.

Bearings are built to exacting size tolerance, and simply swapping and old bearing for a new bearing should not result in the need for new shims.

YMMV

 

[Chevyls6]

A little update on the progress.

I got it all put together and it wont shift into forward. It has neutral and reverse but no forward like there isnt enough clearance between the shift cam and shift pin in the prop shaft.

Disgusted by this i bought a 73 johnson 9.5 and a parts 9.5 for less than the cost of this 9.8 piece of crap.

Anyone know what may have gone wrong ? The shift cam only seems to go in one way since its master splined and tapered at one end. The replacement prop shaft that went in there had a different spring length than the old one but the cross pin hole ends up in the same spot.

 

[Faztbullet]

Dang ..jumped from skillet into da fire...
Remove carrier and reinstall P shaft, Shift into F..does it lock into gear??/ If not your slot is not long enough to allow dog to engage F gear..wrong shaft..

 

[Chevyls6]

Okay if i back off the shift cam as far as it will go all the way until it touches the case it doesn't let the sliding clutch move forward enough to engage the teeth on the forward gear.

The shaft i used was listed by marinengine.com as being interchangeable with the original shaft but i guess they were wrong.

At the time i couldn't find any original shafts on ebay or elsewhere. The prop on this thing must have taken a big hit because the original shaft was bent enough that i could see it without measuring.