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  1. #1
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    Default Re-shimming after re-seal? Alpha 1

    I have a question for the experts about my '86 Alpha One (gen 1).

    I just changed the seal in the outdrive where the input shaft enters. I also replaced the aft yoke and the ring that goes behind it, due to rust damage.

    All the bearings looked fine so were cleaned and returned to their original locations and the pack torqued up to specifications. (This set-up has the small spacer between the bearings.)

    The same shims were replaced aft of the rear bearing so the engagement of the pinion to the driven gear ought to be the same as before. The shims for the driven gear and shaft were not disturbed. Before I filled the oil, I checked for a backlash click when rotating the drive shaft back and forth, and it was present. I tested the whole re-assembled unit at 11psi overnight.

    Later, when I test ran the engine on muffs for a few minutes, everything sounded fine but I noticed that the top of the outdrive had become quite warm. The bottom was cold. I don't know it it ever got warm before but it seems wrong for a no load situation.

    So should I pull the drive back off and get a Mercruiser mechanic to check the shimming or do you think it's normal?
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  2. #2
    Petty Officer 2nd Class Simoniz's Avatar
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    Default Re: Re-shimming after re-seal? Alpha 1

    I know next to nothing about Mercruiser outdrives but I do know that the exhaust runs through it.

    Do you think that could be the reason the top became warm?

  3. #3
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    Default Re: Re-shimming after re-seal? Alpha 1

    nope. as long as no gears or bearings were replaced input shaft shimmng wont be required.

  4. #4
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    Default Re: Re-shimming after re-seal? Alpha 1

    Quote Originally Posted by Simoniz View Post
    I know next to nothing about Mercruiser outdrives but I do know that the exhaust runs through it.

    Do you think that could be the reason the top became warm?
    Well, you're right. You know nothing. The exhaust exits through the bottom part which was cold anyway. It goes nowhere near the top of the out drive.

    Thanks anyway.

  5. #5
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Re-shimming after re-seal? Alpha 1

    Quote Originally Posted by Grumman59 View Post
    Well, you're right. You know nothing. The exhaust exits through the bottom part which was cold anyway. It goes nowhere near the top of the out drive.

    Thanks anyway.
    Guess who knows nothing, exhaust DOES go into the upper first, then turns 90 downward and into the lower unit.
    And yes, it's normal for the upper to get warm. When out on the water, they get downright hot.
    Don S.


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  6. #6
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    Default Re: Re-shimming after re-seal? Alpha 1

    I just replaced the bellows so do know where the exhaust goes. But the prop hub where it exits was stone cold and even the exhaust elbow at the transom was cool.

    Exhaust heat at idle isn't so high and it's only a 3.0L motor. That is why I am concerned about the gearbox becoming hot from a few minutes of idling. The heat was only around the upper gearbox. But if it really was caused by the exhaust, I'll be relieved.

  7. #7
    Petty Officer 2nd Class Simoniz's Avatar
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    Default Re: Re-shimming after re-seal? Alpha 1

    Quote Originally Posted by Grumman59 View Post
    I just replaced the bellows so do know where the exhaust goes. But the prop hub where it exits was stone cold and even the exhaust elbow at the transom was cool.

    Exhaust heat at idle isn't so high and it's only a 3.0L motor. That is why I am concerned about the gearbox becoming hot from a few minutes of idling. The heat was only around the upper gearbox. But if it really was caused by the exhaust, I'll be relieved.
    Well, as DonS points out, the exhaust does indeed go into the upper unit first, albeit not at the top.

    Do you think its possible that in the horizontal run, where the bellows are and the first portion of the run into the upper unit, that the water flow sits at the bottom of the pipe and the (still hot) exhaust gases are in the upper part of the pipe, thus (heat rising) warming the top of the outdrive?

    Maybe the prop hub is cold because its at the end of the down run where the water once again is cooling evenly and its also further from the engine?

    Maybe the exhaust elbow feels cool because when you touch it, you're touching the outside of the water jacket?

    Maybe, if you had rebuilt the drive wrongly, the friction necessary to heat the oil filled top unit for a few minutes at idle would be so great as to stop the thing turning completely?

    Maybe every boat Ive ever been on where, if you lean over the back and put your hand on the top of the outdrive (when its planing and out of the water) and find the top of the outdrive hot, is knackered as well?

    Still, what do I know? Your best bet, mate, is to pull it all apart again.

  8. #8
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    Default Re: Re-shimming after re-seal? Alpha 1

    The cooling water enters the pivot housing below the upper gears and provides no cooling for them.Once the boat's in the water the river will make it feel cooler.I would double check the gear lube level to make sure there was'nt any air trapped when it was refilled.
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  9. #9
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    Default Re: Re-shimming after re-seal? Alpha 1

    All the bearings looked fine so were cleaned and returned to their original locations and the pack torqued up to specifications. (This set-up has the small spacer between the bearings.)
    i did that job too. but i got a mc-1. i had the spacer too. fwiw, and i don't know and didn't research the s/m. but i'd have thought by 86 the spacer would have been removed and ya'd have the other version. might be worth reading to see if ya can fig. which way it's supposed to be. your pics are kinda low resolution but some of the brgs. look a shade discolored to me from the pic. my brgs. were discolored, blued. i R&Red them for that reason alone. i did reshim. funny i ended up with the same shim stack though.

    did ya reinstall the gears with the hash marks lined up? (1.65 gear ratio only)

    I checked for a backlash click when rotating the drive shaft back and forth, and it was present
    i don't know what that means? i thought that's what measuring the engagment of the teeth was for, with the shim tool. .025'' being right. when i did mine. .026'' wouldn't fit, .024'' was too loose, .025'' fit perfect.
    i understand ya could blue the gears to see mesh proper. i didn't do that, just the shimming process.

    Later, when I test ran the engine on muffs for a few minutes, everything sounded fine but I noticed that the top of the outdrive had become quite warm. The bottom was cold. I don't know it it ever got warm before but it seems wrong for a no load situation.
    that does sound a shade odd. i don't think mine gets hardly warm to touch after just a little time of warm up on the muffs. it does get real hot after a run. i have that white stuff on my drive (mineral deposits) after a few runs at the lake. it does get hot. when under load.

    ya can always lake test it. the way i understand it, if ya did it wrong, it won't last very long till it destroys itself. just kidding, kinda sorta. yer gonna have to lake test it sometime. that first half hour will have ya on pins and needles.. .
    Last edited by ziggy; May 11th, 2010 at 07:19 AM. Reason: adj. comment
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  10. #10
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    Default Re: Re-shimming after re-seal? Alpha 1

    Thanks for the replies.

    Before I did this work, I read everything I could find on the subject, the Mercury manual, the Clymer manual, searched the archives here on iboats and I also found this:-

    REPLACEMENT OF OUTDRIVES YOKE AND SEAL -MERCRUISER
    http://amarket.com/merseal.htm

    20) The Shiming should not have changed but the unit should turn effortlessly and you should feel no gap between the gears. There is however a small unfeelable gap that must be there. To check rotate the shaft back and forth rapidly about one inch and you should hear a tapping indicating a light backlash.
    Ziggy, that is what I meant by "listening for a backlash click", and there was backlash present. I don't have the Mercury shimming tools but if everything goes back as before (same gears, same bearings, same shims) I don't see how the clearance can change, just as Rodbolt stated.

    i understand ya could blue the gears to see mesh proper. i didn't do that, just the shimming process.
    Yes, I have a tube of blue and have used it for setting up car diffs but Mercury want you to use their tools instead. It's also a lot easier to read the mesh on a car diff. with blue because it's much larger.

    did ya reinstall the gears with the hash marks lined up? (1.65 gear ratio only)
    No, it's 1.98:1. The marks apply to 1.65 because the gears have the same number of teeth.

    Oil was new Mercury HD and on the level. The gears looked ok afterwards, no coloring or such.

    I'm going to test run it on the muffs again but this time try to ascertain if the heat is coming from the gearbox or not.

  11. #11
    Rear Admiral JustJason's Avatar
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    Default Re: Re-shimming after re-seal? Alpha 1

    As Don said, the uppers get warm. If you've ever been out in the water when the boat is under heavy load, (ie- tubing or skiing) And you go to get back into the boat by using the drive to stand on, the top cap will be extremely hot to the touch. It's all normal. Tapered bearings create heat when running, gears putting oil under tremendous pressure create heat, and heat rises... so what part of the entire drive do you think gets the hottest?
    just because you found it that way... doesn't mean it's supposed to be that way.

    Part of diagnostics is spending time figuring out not only what the problem is, but also sorting through what it isn't.

    The older the engine is, the chances of it having more than 1 problem goes up exponentially

    Boating has always been a rich mans hobby. Buying a new boat gets cheaper every year, but the maintenance, the repairs, and the overall cost of ownership of a boat has never gotten any cheaper.

  12. #12
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    Default Re: Re-shimming after re-seal? Alpha 1

    OK, I ran the test again, running on the muffs for about 10 minutes, both in and out of gear.

    The temperature of the upper gearbox steadied at about 100 deg while the area underneath where the exhaust enters was about 80 deg. The prop hub where it exits was cold, about 50 deg which is the ambient temp here today. The motor temp steadied at 140.

    So it looks like there is certainly heat generated by the gearbox itself although I don't think 100 deg is a problem. Thanks for all the replies.

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