1977 Johnson 70 Exhaust Manifold Gasket/ Powerhead Removal

Cherokee-Runabout

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May 30, 2012
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Brought the Lund out after hibernation for the winter and went to give the initial test-fire on the muffs and she started up flawlessly. After removing the cowling and looking everything over I noticed a small stream of water coming out of my center exhaust manifold gasket. The gasket appears to have been pushed out and split and I am unsure of the age of it sense I only bought the motor a few years ago. Anyhow to make a short story longer, I don't have very many specialty tools and was wondering whether the removal of the carbs, leaf plate, and fuel pump is necessary to remove the powerhead as well considering I only need access to the exhaust manifold. Having never pulled a powerhead before I didn't know if there were any shortcuts or if I should just strictly adhere to the service manual. Also should I have any concern about the leak or assume that it is just a cracked gasket? Any help is greatly appreciated and I guess I'll be fishing from the canoe for now! Hopefully tomorrow I'll be able to add an image of the affected gasket.
 

emdsapmgr

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Dec 9, 2005
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The exhaust covers are on the port side of the engine. It's not unusual for those 3 gaskets to shrink after many years, causing the initial bolt torque to loosen up. Once that clamp load goes away, the gaskets can be prone to leaking. You should be able to remove the covers without removing the powerhead. The service manual does not specifically call out the torque for those bolts, but there is a generic torque spec for all bolt sizes, usually in the front of the manual. Once you replace the gaskets, you will want to retorque those exhaust cover bolts after the engine goes through a couple of heat/cool cycles.
 
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Cherokee-Runabout

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May 30, 2012
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Thanks for the info! Yest the exhaust covers are on the port side of the engine, however, I think that this repair will require me to pull the powerhead as I cannot access the bottom two bolts without either cutting or drilling out the lower cowling. Final question tho.... Is it necessary to remove the carbs, leaf plate, etc... as per the manuals instructions? Once again, thanks for any advice.
 

emdsapmgr

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I've had two 3 cyls, but have not had the pleasure of removing the exhaust covers. It's possible that you may be able to loosen the lower cowling enough that you may be able to remove the cover/bolts. There are 4 brackets that secure the lower cowl to the powerhead. You may be able to remove the bolts through those brackets so that it will loosen up. You will probably have to remove the two lower exhaust covers (front and back) under that lower cowling.
 

Will Bark

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Aug 1, 2010
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Had one friend with same motor who just drilled two holes in cowl to get socket to the bolts and then plugged the holes up. Have another who took a Dremel cutoff tool and slicled a section out to get to the bolts. His cut was so precise that it looked like it had been done at the factory; I couldn't do it myself. But both methods worked well and saved a lot of time. Good luck
 

Cherokee-Runabout

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May 30, 2012
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Thanks for the suggestions! I'm still a little hesitant about cutting it out although that does seem to be the simplest solution. Maybe beforehand I will determine the feasibility of emdsapmgr suggestion, I'm just not too fond of chopping my baby up:facepalm:, however that may well be the simplest fix. I'm planning on tinkering with it this weekend, still waiting on the shop to get my new gaskets in. Happy boating and once again thanks for the suggestions.

Also, did your friend just epoxy the piece he cut out back in?
 
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racerone

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Dec 28, 2013
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Removing the powerhead is actually easy to do.---Working with the powerhead laying horizontal makes installation of the gaskets much easier.--Gasket under the powerhead likely needs replacing too.
 
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