77 Johnson 35HP oil leak

[Jeff74]

could a bad top seal cause oil to leak from right under the armature plate at the top of the powerhead? 77 Johnson 35hp. leaks a lot of oil down from the top of the power head, down the exhaust housing and into the water. Looks like the leak starts right where the powerhead meets the armature plate. Would like to fix this, don't want to be the guy who kills all the fish...

ishopmarine.com sells the seal and the top seal puller tool. Am I on the right track?

Thanks-Jeff.

 

[emdsapmgr]

Re: 77 Johnson 35HP oil leak

Yes. You probably have a bigger problem than just the seal. It is common for high hour engines of this type to wear the upper crank bearing, 386481. The bearing gets sloppy. When this happens, the crank tends to "rattle" around in the upper bearing, taking out the upper seal. In order to repair this, you will need to split the crankcase halves, replace the upper bearing and install a new seal. You will be suprised how much quieter the engine is with a new upper bearing.

 

[Jeff74]

Re: 77 Johnson 35HP oil leak

Thanks for the reply. Do I have to pull the whole powerhead off, or can I just separate the front half away? Thanks-Jeff.

 

[rodbolt]

Re: 77 Johnson 35HP oil leak

first try to rock the flywheel fore and aft, most any perceptible motion indicates a worn bearing, the try to pull up and down on the flywheel, any motion indicates a worn bottom main. both will require complete powerhead dissasembly to correct. if you feel no motion then replace the seal and see what happens.

 

[Jeff74]

Re: 77 Johnson 35HP oil leak

Thanks for the advice. I was hesitant to jump straight to a major overhaul. We'll see what happens. This is a great forum. -Jeff.

 

[reeldutch]

Re: 77 Johnson 35HP oil leak

yes the powerhead has to come of to split the block and reseal the block.

 

[Jeff74]

Re: 77 Johnson 35HP oil leak

Ok, so it looks like I'm going to have to replace the bearings. I've done lower unit work replacing the gears and clutch dog and carb cleaning, but this may be beyond my skill level. It looks like I can't even get the flywheel off without a special tool of some kind.

I talked to a repair guy in San Antonio (I'm in Austin) who sounds like a good guy. jerry's recreational. Over the phone, he figured I was looking at about an $800 job with labor. Sound about right? He'd even come up to my place to do the work.

Also he recommended replacing piston rings while we were in there. Sounds like a major overhaul. I guess it is worth it. The engine runs great, I guess an overhaul is due after 30 years! Any thoughts would help. Thanks!-Jeff.

 

[emdsapmgr]

Re: 77 Johnson 35HP oil leak

Since you will have most of the engine down, you'll need an engine gasket kit.
New rings would be advisable, as it will extend the life of the engine. (make sure you hone the cyls). I'd put in a new thermostat and impeller at the same time.

 

[67Johnson6HP]

Re: 77 Johnson 35HP oil leak

Given that you have worked on the l/u and carb you may be like me - More sense than money. With a good manual and the help of the guys here I'm sure you can do it yourself a lot cheaper. You'll have to buy some tools, probably, but it will still be a lot cheaper than $800.

 

[F_R]

Re: 77 Johnson 35HP oil leak

Don't be surprised if you are in for a surprise. The top main is a roller bearing that rolls directly on the crankshaft. It's very unlikely that the bearing is worn without taking the crankshaft with it. A new crank is $418, the top bearing is $41. And then there's the lower main and ........

 

[Jeff74]

Re: 77 Johnson 35HP oil leak

Thanks. This just keeps getting better...-Jeff

 

[Jeff74]

Re: 77 Johnson 35HP oil leak

Anyone know how to get the flywheel nut off? Is there a special tool of some kind? I have the puller, but have to get the nut off first. Thanks-Jeff.

 

[F_R]

Re: 77 Johnson 35HP oil leak

Nothing special, just a big wrench to fit. Of course, you have to hold the flywheel from turning. Lots of ways to do that. Yes, it is tight and when you get around to putting it back together, use a torque wrench to tighten it to specs or you will wreck another crankshaft.