outdrive ratios

[husaburg560]

I have a 82 merc pre alpha model 1 drive, that has a 1.65 ratio. problem is the shaft that the u- joints connect to is wore out and the seal is not sealing. I have already disassembled it. A friend of mine gave me a 1980 model pre alpha model 1 drive complete upper and lower units, they have very low hours on them, only thing is it has a 1.84 ratio. This is the only thing different about them. I switched them out. Now I have a slower top end, which makes sence of the higher drive ratio. I want to change the gears in the upper housing. When I do this should I use the shims out of the 1.65 drive or the shims out of the 1.84 drive? I have built several rear ends in cars before and have always set them up with 3 to 5 thousandths backlash on the gears and they run great. Just wondering what you guys think.

 

[Laddies]

Re: outdrive ratios

You really need a manual and shimming tools for the job, why not just switch driveshafts and yokes they are the same

 

[rodbolt]

Re: outdrive ratios

not that I reccomend moving the seal. I reccomend replacing the yoke. but in a bind on a weekend I have been known to alter the seal location in the seal carrier. to do this properly reqiues some thought. the seal must be kept square in the bore of the carrier. to do this cut a .03" shim to fit the carrier bore. then use a flate plate and a press. place the carrier on the plate, place the shim in the carrier and let it rest on the plate. then press the seal in so it hits the shim. you have now succesfully moved the seal aft in the carrier .03" and it will be on a good surface of the yoke. its a bit of engineering but it works. but I always reccomend to replace the yoke.

 

[Don S]

Re: outdrive ratios

I agree, replacing the yoke is the best method of repair. Below is a link for the service manual for the drive. You will be able to see that shimming an alpha drive requiers lots of special tools that cost a lot more than a yoke for your original drive. The Mercruiser PN for the yoke is 46020 1 and lists for $75, a lot less than the shimming tools required.<br /><br />Move your curser over the page in the manual and index to locate the links to the different sections.<br /><br /> http://www.boatfix.com/merc/Servmanl/6/6covr3.pdf

 

[husaburg560]

Re: outdrive ratios

I have a spare out drive with a good yoke and seal in it. My main question was switching the drive gears from one housing to another housing. My upper housing has a rib on the bottom broken off, is why I don't want to use it. It appears the shims only control how far or how deep the gears mesh. There is no side to side adjustment, or backlash on these units. The timken bearings locate the gears. Couldn't I just use some white litheum grease on the gears and rotate them, and shim accordingly to get the grease pattern in the middle of the two gears? Thanks everyone

 

[bigbrownbuku]

Re: outdrive ratios

yes you could just blue the gears to get the correct mesh. they do have backlash which you can find in dons link.<br />if you are going to reuse the nut use loctite.<br />its possible to align the bearings without the large hose clamp. another option to "repair" the input yoke is a sleeve.<br /><br />1.65 gear sets are hunting sets, make sure to realign them.<br /><br />the bearings dont determine gear height. shims do.