Bearing replacement, or not?

[petrolhead]

Hi guys, it's been a while since I posted here, too busy building my boat but now I need to ask a question about my Johnson 18 FD-12.<br />Some time ago when I bought the engine I had it checked out by the local outboard specialists, they told me that it needed all new ignition components, HT leads, carb kit, etc..., they also told me that the upper shaft bearing was worn and needed replacement.<br />I've got all the parts I need including a new bearing, but now I've started to strip the engine I'm beginning to wonder if there's actually anything/much wrong with the old bearing.<br />When I grasp the flywheel and rock it side to side and back to front, I do feel a very slight movement, like a couple of thousandths of an inch at the flywheel rim, which must translate to less than one thousandth at the bearing. Is this too much and should I replace it?<br />I have reason to believe that this outboard place is not being entirely honest with me, several times I've been there for advice and parts, to be told that simple things like cables and connectors are unavailable, only to find that they are! <br />I get the impression that they are trying to get me to pay out for expensive and unneccessary work, or are hoping I'll just give up and they can sell me a new engine!

 

[R.Johnson]

Re: Bearing replacement, or not?

There is a upper crankshaft seal pressed into that upper bearing. If you see oil on the mag. plate, thats where it came from. It takes a special puller, and driver to replace this seal. I would bet that is the only problem you have. If the seal gets really bad you could have an air leak at this point. I would run it first, and see how it does. Just don't try to pry that seal out with a screw driver. Post back, we will help you along.

 

[petrolhead]

Re: Bearing replacement, or not?

The seal is definitely not leaking at all, that's one of the things my manual tells you to look for, I did and there's no trace of oil on the mag plate or below now that I've removed it. Would a leaking seal show up as play in the bearing though?<br />I guess what I'm asking is what's a reasonable amount of play in that bearing before I should consider replacement?<br />I get the impression that this engine has seen little use in its 46 years, and excessive bearing wear seems very unlikely when everything else about it mechanically is so good.

 

[R.Johnson]

Re: Bearing replacement, or not?

I don't think you have anything to worry about. The crank runs in roller bearings on that engine. There will be a slight amount of play. About the only thing that will damage those bearings is lack of oil, in this case the rod bearings would be the first to go. As I said! I don't think you have anything to worry about. My son, and I have two of those engines, we run them several times a week all summer, and they have never been rebuilt.

 

[petrolhead]

Re: Bearing replacement, or not?

I wondered about lack of oil to the bearing, the upper bearing gets its lubrication through that skinny little tube up the side of the crankcase, so I was going to disconnect the top end and blow it through to make sure it's not blocked.<br />I think it's probably safe to run the engine as it is, with the tiny amount of bearing play I don't see that anything catastrophic can happen, one day I may strip the whole block down and do it then.<br />As you seem pretty familiar with these engines, what do you think of the pressurised fuel tanks, are they any good or should I consider fitting a fuel pump and a single hose tank?

 

[Hooty]

Re: Bearing replacement, or not?

If you had had a lack of oil, it would have shown up in the rod bearings like Senor Johnson said. If it has suffered lack of oiling anywhere, the crankshaft will be badly discolored and probably scored. <br />Put it back together and run it like a borrowed horse.<br /><br />c/6<br />Hooty

 

[cajun555]

Re: Bearing replacement, or not?

I've got a 56 Jonny. Still using the pressure tank. I've thought about changing over to the fuel pump and vented tank, but reading what the "pros say" I'll stick with the pressure tank. If you need a tank I've seen them on Ebay. Also you can get rebuild kits for the tanks as long as it not rusted out.