OMC 400 lower

[Asymetric]

Hey all Been a lurker here for a few years but now i have a problem that im hoping some of you may be able to help with.

Over the winter i replaced the vertical shaft in the lower unit of my OMC 400. Aside from removing and replacing that big snap ring, i was suprised at how smooth the job went.

I kind of knew better in the back of my mind, but i replaced the thrust bearing and re used the same shim setup that was on the old shaft. After running it in the driveway, everything shifts good, but after about 15 - 20 mins of running in the driveway, i got one metal chip on the upper plug magnet and 2 on the drain magnet.

I havent taken it apart yet, but im near certain that its going to be the thrust bearing on that shaft. Is there any way at all to determine how much shim i need to remove? I am a machinist by trade so im no stranger to tight tolerances and measuring instruments. I saw a tool for sale that is for dooing that, but would rather avoid spending that kind of money for somthing ill probably only use once.


I am open to any suggestions

 

[fendersfender]

Re: OMC 400 lower

your drive definitely needs to be dissassembled and re-shimmed to specs....as far as needing that special tool, i'm not quite sure if there is some other way to measure for shimming or not...i'm sure someone else will chime in with some more info

 

[Asymetric]

Re: OMC 400 lower

If it just needs to be a certain dimension, i can measure that. We have one of these
http://www.starrett.com/pages/691_optical_comparators.cfm
at the shop at work for measuring odd shapes and angles. Just dont know the required dimension or what points to measure from.

 

[HT32BSX115]

Re: OMC 400 lower

My Cobra manual is pretty specific on how to do it....
Doesn't the OMC service manual indicate how/where to measure and shim?

 

[Asymetric]

Re: OMC 400 lower

The manual i have tells me to put it in a jig and use a special guage OMC part #blabla. Then measure between the end of that guage tool and the gear with feeler guages and shim acording to the gap thats there, If i knew the actual length dimension, i could just measure and shim acordingly without buying anything.

Today i dropped the lower unit and sure enough that thrust bearing had 3 rollers that had some of the hard facing chipped off. I replaced the bearing and removed a .005" shim. Ran it in gear in the driveway for a good while and took it back apart to inspect it and all looks well. Well see after i get it in the water tomorrow where there will be an actual load on it.

I borrowed a friends trolling motor tho just incase. Dont want to be stuck drifting onto the rocks.

 

[HT32BSX115]

Re: OMC 400 lower

I'm afraid you'll need that trolling motor.

Outdrive problems usually show up under load.
If you don't want to buy or build the Shim Guage (like this one ) it might be better to just find yourself another rebuilt lower on ebay or something. All these tools show up on ebay every now and then.

If I had one I'd be glad to loan it to you...or measure it accurately so you could build one. I have no OMC tools now....only some OMC parts that are slowly but surely going away.

Cheers,


Rick

 

[Asymetric]

Re: OMC 400 lower

Well i took it up the river a few miles and back today and theres no more metal on the magnets. Diddnt hear any audible whining from the outdrive, but im a little paranoid about what damage that little bit of shavings may have done to the rest of the bearings. Im going to stew on it this week, but ill probably end up tearing it all back down next weekend to have a look for myself.

If anyone else has the proper shim guage and a descent set of calipers to measure it with, i would really apreaciate a dimension so i know its in there right instead of trial and error on the shims. My favorite walleye spot is a good 25 miles or so offshore.

Thanks for the input sofar.

 

[fendersfender]

Re: OMC 400 lower

i dont understand why omc insisted on using their shim tools instead of giving a dimension that could be measured with a veneer or calipers is a mystery to me.....if i could find a set for my 800 series i'd buy them

 

[TitusAdronicus]

Re: OMC 400 lower

A friend of mine rebuilds drives for a living and he told me that the tolerances in these drives are tighter than in the engines. the spacing on the gears and bearings are vital. My feeling is to let someone who has already invested in all those special tools and has the know how to work with those tight tolerances do the work.