Bearing and cap replacement on alpha one

[mattell]

Purchased my first boat 87 Marlin 120hp mercruiser with alpha one. The bearing on the upper drive seems to have frozen to the shaft and scored the cap. The gears look ok (not broken and turn smooth). i want to clean it out good and change bearing and cap. looks like it ran dry but Im willing to take a shot. I know from reading here this is a can of worms and just trying to get the boat running without my wife giving me an I told you so. Question 1. Do I have to remove the drive shaft to do this and if so can i replace everything back in the order it came out because I am using same gears and spacers. The spacer in the cap to load the bearing is it straight forward? 2. will the oil seals be accessable and easy to change? Boat shop says 500-2500 depending on damage. Replacing pump is a given already purchased it before i discovered this. Looks like remove spanner nut, pull out gear and pull up and out shaft. If the bearing is pressed on the shaft I can take the shaft to machine shop. I was hoping the bearing was pressed in the cap and slipped onto shaft.

 

[muc]

Re: Bearing and cap replacement on alpha one

You will need to reshim when you replace the bearing and cap.
You might want to disassemble both the upper and lower to clean out the metal that was created when the bearing spun. The procedures are covered in the service manual. The tools are a little spendy and the experienced mechanic costs could be worth it?

 

[Bondo]

Re: Bearing and cap replacement on alpha one

is it straight forward?

Ayuh,... Only if you Know what yer doin', 'n have ALL the speciality tools...

 

[ziggy]

Re: Bearing and cap replacement on alpha one

1st, i'm just joe boater, not a marine tech. + i work on my mc-1 drive which is only similar to your alpha1.

Question 1. Do I have to remove the drive shaft to do this and if so can i replace everything back in the order it came out because I am using same gears and spacers.

if ya use the same gears and brgs. i don't think you need to reshim

The spacer in the cap to load the bearing is it straight forward?

these are the shims. the way ya know if ya got proper shim stack is to test w/ rolling torque on the drive gear drive shaft. i've not read s/m #6, but for my pre alpha, that rolling torque is 6-10 in. lbs. look in your s/m to find proper spec for your rig.

2. will the oil seals be accessable and easy to change?

i don't know, i havn't done that. but i believe there's likely special seal drivers necessary. again, the s/m will let ya know the facts.

Looks like remove spanner nut, pull out gear and pull up and out shaft.

yep, take top cap off, remove retainer nut, pull drive gear assy. out, then pull driven gear drive shaft out.

If the bearing is pressed on the shaft I can take the shaft to machine shop.

that's what i did. but i took it to my local mercuriser dealer to have them press the brg. off. + extract the race and R&R that too.

a like to the woes i had. might give ya some insight.. http://forums.iboats.com/showthread.php?t=456307

use your oem service manual. it's a must have tool for your project.

 

[mattell]

Re: Bearing and cap replacement on alpha one

Well could not get the bearing off with a puller. Un believable. arc -aired the bearing on both sides and got it off. new bearing, shimmed the cap 6 rolling ft pounds, cleaned the upper gears and bearings, installed new pump and fluid. will water test next week. 71 bucks for parts. keeping my fingers crossed. Buying seatow before i go

 

[ziggy]

Re: Bearing and cap replacement on alpha one

shimmed the cap 6 rolling ft pounds

hope that's a typo..
from sm #6, pp 3a27
USED BEARINGS: 2.5-4 lb. in.
NEW BEARINGS: 6-10 lb. in.

 

[Don S]

Re: Bearing and cap replacement on alpha one

hope that's a typo..
from sm #6, pp 3a27
USED BEARINGS: 2.5-4 lb. in.
NEW BEARINGS: 6-10 lb. in.

Even if you did get the preload right and in inches, not ft lbs, did you go back and check gear height with the special tools? If you didn't you can bet money it's off unless you had exactly the same preload as it had before, the gear height will be off, and therefore the contact pattern and backlash will be wrong.

 

[Howard Sterndrive]

Re: Bearing and cap replacement on alpha one

Boat shop says 500-2500 depending on damage.

brand new SEI upper with 3 year warranty is $645