Alpha One Gen 2 Top Cap Bearing Slipping

Sashap

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I have a new bearing race and a replacement top cap. When I put in the new bearing race cone, it went in normally stiff. However, after an hour of boating, I took off the cap to inspect and the bearing just fell out!
I purchased some Loctite 660 (fricking expensive stuff) and let it cure 48 hours. Went out again for an hour and it just slipped out again! I even tried putting dimples in with a punch all around to make it fit more snug. When I inspected the surfaces after the ride, it was smooth as can be and not a trace of the 660 in there. I did not use the primer as I was told I didn't need it. I will get some tomorrow.
However, My question is what am I missing? How can I make it not do this? Does the peening the surface help? How many dents should I put in? The difference in size is .003" so I am well within the tolerance of what loctite 660 can handle.
Ideas? Thoughts? I don't want to hear the usual "advice" of "go buy a brand new one...I'm not convinced it wouldn't happen with a new one either.
 

alldodge

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You may need to get a new top cap. Did you see this in the manual, shows 0.157 difference in diameter

bearing.jpg
 

harringtondav

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^^+1. Any time you change a tapered bearing race, roller assy, or the set you need to recheck shim height or preload. The assembled height can vary up to .005". If this bearing's preload is too high, the race may spin from the excess force. Too little, or no preload (clearance) the bearing set will side load and could cause race creep - rotation.

I had a similar problem and the Loctite/Henkel rep recommended 638. It has their highest shear strength of >25N/mm2, max diametrical clearance of .25 mm/.010". Your 661's strength is >15N/mm2, clearance of .15mm/.006". 67% stronger with larger gap fill.

638 is also pricey, >$20 for the little 10 ml bottle. But a little dab will do you....many times over. Clean the cover bore well with acetone before reassembling. But you really need to follow the preload process to be sure the shim pack is correct before using the Loctite.

Locktite.JPG
 

AShipShow

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After setting the preload and reassembling, check your top cap while the boat is running on muffs, if the bearing race is still spinning, the top cap is going to be getting extremely hot which is probably also why the loctite failed.
 

Sashap

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145
^^+1. Any time you change a tapered bearing race, roller assy, or the set you need to recheck shim height or preload. The assembled height can vary up to .005". If this bearing's preload is too high, the race may spin from the excess force. Too little, or no preload (clearance) the bearing set will side load and could cause race creep - rotation.

I had a similar problem and the Loctite/Henkel rep recommended 638. It has their highest shear strength of >25N/mm2, max diametrical clearance of .25 mm/.010". Your 661's strength is >15N/mm2, clearance of .15mm/.006". 67% stronger with larger gap fill.

638 is also pricey, >$20 for the little 10 ml bottle. But a little dab will do you....many times over. Clean the cover bore well with acetone before reassembling. But you really need to follow the preload process to be sure the shim pack is correct before using the Loctite.



Thanks,
This is what I suspected. I have a temperature set up that I programmed myself to measure the running temp of the top cap and at plane, I am running 120-130 degrees, so I think this is the issue. My boat parts supplier is sending me a cap with a bearing cone already mounted so I will set it with that and then take off the top part of the leg and check the preload. I have a feeling that it's high also because the original cap actually sits a bit high prior to tightening the bolts. The original cap had the bearing cone and shims replaced but I did not check preload...oh well...
I will try the 638 if I have to remove the cone and reshim.

Do you know if the 638 needs the primer as well? And by the way, in Canada, the cost for 630 is $60! Whatever, it is worth the cost to get it right. Thanks for everybody's input. Will repost when I get it right to confirm.
 

Bt Doctur

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My boat parts supplier is sending me a cap with a bearing cone already mounted so I will set it with that and then take off the top part of the leg and check the preload. I have a feeling that it's high also because the original cap actually sits a bit hi

Preload is measured with the top cap in place and tightened. The preload in question is a rotating type of preload. Do you have the mercruiser manual?
 

harringtondav

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If you check preload with the lower housing drive shaft seals installed you will need to measure and record the 'base line' rolling torque caused by the seal drag on the shaft. This drag can be as much as the specified bearing preload. With the input drive shaft assembly removed, and the top cap shimmed up 1/8" with washers check and record the drag several times. Then remove the washers and torque the cap to spec and follow the procedure. Subtract the base line torque to get the actual bearing rolling torque preload.

Increase preload my adding shims under the cup/race. Reduce it by removing shims. You'll have to pull the race to do this. Use the shims from your old cap assembly to get the correct shim thickness. You'll need a micrometer or caliper to measure the starting shim pack thickness, and the thickness of an adjusted shim pack. Small changes - .002"-.005" make a big difference. It can be a trial and error process, so you may end up pulling and pressing the race a few times. Make sure the race is fully seated. A dab of RC will insure it stays put. But it will take heat if you need to remove it in the future.

Loctite stated primer isn't required for steel-steel applications. Steel-aluminum..?? I cleaned my cap well with acetone before race application and RC 638 and it's stayed put.
 
Last edited:

Sashap

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If you check preload with the lower housing drive shaft seals installed you will need to measure and record the 'base line' rolling torque caused by the seal drag on the shaft. This drag can be as much as the specified bearing preload. With the input drive shaft assembly removed, and the top cap shimmed up 1/8" with washers check and record the drag several times. Then remove the washers and torque the cap to spec and follow the procedure. Subtract the base line torque to get the actual bearing rolling torque preload.

Increase preload my adding shims under the cup/race. Reduce it by removing shims. You'll have to pull the race to do this. Use the shims from your old cap assembly to get the correct shim thickness. You'll need a micrometer or caliper to measure the starting shim pack thickness, and the thickness of an adjusted shim pack. Small changes - .002"-.005" make a big difference. It can be a trial and error process, so you may end up pulling and pressing the race a few times. Make sure the race is fully seated. A dab of RC will insure it stays put. But it will take heat if you need to remove it in the future.

Loctite stated primer isn't required for steel-steel applications. Steel-aluminum..?? I cleaned my cap well with acetone before race application and RC 638 and it's stayed put.

So, the crap continues...
I installed the the replacement cap yesterday with loctite 660. That is what was recommended. After checking that the preload for the shaft with the cap shimmed less than before I got a mid range setting of about 5 inch pounds. Upon doing a test run this morning, I saw that the running temperature of the cap was around 80 degrees farenheit maximum. That is way lower than the previous temperature of 130 telling me that at least the load is not obviously as high as before. The lake temperature is 71 so that sounded about right. So I went out again this evening and same good low temps. However, when I took the cap off when I got home, the bearing cone was again spinning! I used acetone to clean it all. SO, once again, I flushed it with acetone, then cleaned it all again really well and re-applied the bearing cone. I couldn't spin it after application but honestly, I am not holding my breath. This is beginning to really get on my nerves.

I read everything I could find, I saw videos that thoroughly explained how well this stuff holds loose bearings almost instantly due to the ionic exchange with the steel. What is really concerning me is that I just can't get the same easy results. Just like those as seen on tv commercials, when you get the stuff home, it doesn't work at all the same. I know there are other grades like 638 but everything points to the 660 being what I should use. There is no lateral movement to the cone so I don't have too much slop or anything like that. But, really I just don't know what else to do. I don't want to take it to the one mechanic here in town because I probably won't see the boat until September if I do.

The original cap had the bearing glued in with 660 as I could see the residue of it on the inside after a horrible time of trying to remove it. The old bearing was burnt and I needed to change the cone because it was all brown from overheat and had score marks. I should have just left it in there because it was really stuck and I had to cut it out it was so well glued. I just don't know what else to do.

I am tempted to drill a pin into the cone from the outer edge and glue it in there. I know that is totally wrong but that is how desperate I am. I see all of these great prices for SEI top units in USA but here in Canada they are way more because of exchange and just because it's Canada...nothing is cheap here! I know that buying a new one is a stupid solution too. I have all new seals, gears and bearings in mine. Just this stupid top cap issue.

I'm so lost.
 

Sashap

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is loctite 638 really better than the 660? I put the 660 on last night to my old cap after cleaning and flooding with acetone. I tried removing with a bearing puller and it did not budge. I am willing to bet though that today's boating will loosen it... I will keep you all posted. I know that it could still be that I mis-measured the preload, But I am down to only 2 shims compared to the old one having 4. Yes, I did change the gears also, so maybe that's correct.
 

Sashap

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Well, after an hour of boating...loose cone...again. I had prepared 2 spares prior to going out and I changed one and when I got home, checked again and again a loose cone. I honestly think the 660 is too thick for the application and what is left between just isn't enough. I found the permatex equivalent to 638 and will try that next time.

There are only 2 thin shims in there. Hardly anything. Could it be that the bottom shim on the main bearing cone on the bottom of the shaft is too thick? I could not check clearance for that when I was installing the new gears as I do not have or have access to the proper tool for checking. The gear wear looks ok after 20 hours though. I'm thinking if the 638 doesn't work, then I will have to figure out where I can get the clearance checked nearby. This place is really difficult to get good service and quickly.

Is it possible that I have too much clearance? My custom thermistor microcontroller showed no abnormal temperature spikes like previous episodes. The running temp is totally normal looking.
 

Sashap

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I finally got around to dealing with this. I have determined that even with no shims I have a few inch pounds too much preload. I only have 2 shims under the bigger cone at the bottom of the shaft. However, now I can't remove the lower bearing cone because I don't have a bearing puller that would fit a larger cone. I know this sounds odd, but I have tried and can't remove the bottom cone at this time. Like I said, there is very little under it so I don't know how this could be so high. I tried ensuring that the bottom cone maybe is not seated all the way down, but nope it's tight down. Ideas? Thoughts?
I am measuring at 6-8 inch pounds now with cap on. That is high as I see it should be almost half that.
 

Bt Doctur

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you may have to alter a small slide hammer jaw to fit the recess under the race
 

Sashap

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I know this might not be totally correct for the gears, but I managed to find a bearing cone (I have a bunch...don't ask) and one was thinner than the rest and I managed to get the preload in range (still with no shim). I just want to do a test run to see if this preload range holds the bearing in the cup without slipping. I added some loctite bearing to it prior to pressing in. I could not measure the gear height as the place that I was going to borrow the tool from was conveniently closed today. Again, just wanted to see if the cup spins like it did before. It was substantially better in the preload range though and I could even noticeably feel the difference when spinning the torque gauge. The thinner bearing also dropped the torque range as much as 4 inch pounds, it was that much thinner.
I know that I have to balance shims both up and down to make a balance. I will get the shim tool and redo it after my test. I just want to finish out the year before tearing into it again. I'm only going to put a maximum of 4-8 hours on it by end of season and half of that will just be trolling. Honestly, I'm to the point that if I have to get a replacement used upper that I'm ok with it. Just wish that prices in Canada were not so stupidly high. The same $600-$700 upper unit in the land o' Trump costs $1100 here plus taxes...of course there is the exchange rate difference too.
 

Sashap

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May 1, 2016
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should anyone care...4hours service time later and the top cap bearing is good!
but, the starter bolt sheared now!
 
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