1970 Mercruiser 165 MC-1 upper unit reseal

[LDO6490]

Found a good amount of drive oil dripping out the lower unit seep hole. Recently replaced my shift shaft with s.s. one and new seals so no problem there. Also entire water pump assembly replaced so no worries there. Two seals behind prop replaced as well. Oil is dripping down lower drive shaft so upper seals leaking. Smaller of the seals is visibly worn on the sealing lip. Lower drive shaft is fine with no wear where the seals contact. Just going to reseal the entire upper while I'm at it. The yoke seal seems pretty straight forward, thanks to instructions from mercstuff.com. Many hints there regarding pre-load, etc. One question though, the merc service manual is hard to decipher when it comes to removing the upper drive shaft in order to replace the larger of the two seals. Am I going to need to press any bearings/races on and off or is it just free to come out after I get the u-joint shaft/bearing assembly out and I remove the top cap? I can usually figure out the service manual, but I'm struggling with this one. Figured I better ask so I'm prepared for what's needed. Thanks!

 

[achris]

Re: 1970 Mercruiser 165 MC-1 upper unit reseal

Remove the front bearing pack (with yoke and drive gear), then remove the top cover. Reach in and pull the driven gear and upper drive shaft straight out. Pop the seals out, clean the seal surfaces THOROUGHLY before putting the new seals in. If you still have the 'O' ring on the top of the lower drive shaft, trash-can it! That 'O' ring has a nasty habit of fouling the lower of those 2 seals in the bottom of the top box and holding it open, allowing water into the spline area. Pretty soon, no splines!

Chris......

 

[LDO6490]

Re: 1970 Mercruiser 165 MC-1 upper unit reseal

Thanks Chris. That cleared the upper shaft removal procedure up. With regard to trash canning the o-ring on top of the lower drive shaft, do you mean not using one at all or just make sure and replace it with new?

 

[achris]

Re: 1970 Mercruiser 165 MC-1 upper unit reseal

Thanks Chris. That cleared the upper shaft removal procedure up. With regard to trash canning the o-ring on top of the lower drive shaft, do you mean not using one at all or just make sure and replace it with new?

Not using one at all...
(New shafts from Merc are without the 'O' ring groove anyway now...)

 

[LDO6490]

Re: 1970 Mercruiser 165 MC-1 upper unit reseal

The upper re-seal job is done. No issues. Thanks Chris for the advice on getting rid of the top o-ring on the lower drive shaft. I discovered pieces of old o-ring in above and around the splines of the upper shaft socket. Obvious they caused the demise of my oil seals. Won't be using an o-ring there anymore. Thanks!

 

[AzFisherman84]

Re: 1970 Mercruiser 165 MC-1 upper unit reseal

Remove the front bearing pack (with yoke and drive gear), then remove the top cover. Reach in and pull the driven gear and upper drive shaft straight out. Pop the seals out, clean the seal surfaces THOROUGHLY before putting the new seals in. If you still have the 'O' ring on the top of the lower drive shaft, trash-can it! That 'O' ring has a nasty habit of fouling the lower of those 2 seals in the bottom of the top box and holding it open, allowing water into the spline area. Pretty soon, no splines!

Chris......

I'm new to the boating world so bare with me, when you say pop the seals out. What I'm using to pop out the seals and direction are those two seals suppose to come out? Thanks

 

[Bt Doctur]

Re: 1970 Mercruiser 165 MC-1 upper unit reseal

for the input shaft seal,when you remove the input shaft you remove the nut, pull the yoke away from the gear, remove the gear from the bearing package
if new style gears were installed you will need a gear puller to get the yoke out the gear.press the old seal from the carrier and press the new one in till flush.If the yoke pulled out ,reassemble and tighten not to 70ft/lbs, If the gearset must be pressed on ,you will use the rolling torque method.
The upper case seals, the small one can be popped out using a long screwdriver or driven from the inside out, the larger seal is driven from the outside in. install new seals in the opposite direction.

 

[AzFisherman84]

Re: 1970 Mercruiser 165 MC-1 upper unit reseal

for the input shaft seal,when you remove the input shaft you remove the nut, pull the yoke away from the gear, remove the gear from the bearing package
if new style gears were installed you will need a gear puller to get the yoke out the gear.press the old seal from the carrier and press the new one in till flush.If the yoke pulled out ,reassemble and tighten not to 70ft/lbs, If the gearset must be pressed on ,you will use the rolling torque method.
The upper case seals, the small one can be popped out using a long screwdriver or driven from the inside out, the larger seal is driven from the outside in. install new seals in the opposite direction.

Thanks Bt Doctur, that helped a lot. I have one more question; is it worth buy the seal driver and the driver rod sold by Sierra to help with the installation or can I bump them in with an long screwdriver?

 

[LDO6490]

Re: 1970 Mercruiser 165 MC-1 upper unit reseal

I used a universal seal driver set from Harbor Freight. Cheap and easy.

 

[AzFisherman84]

Re: 1970 Mercruiser 165 MC-1 upper unit reseal

Thanks for all the help. My upper unti re-seal job is done. thanks again