Crankcase Gasket Leak? [Pic]

79 Silverline

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Jul 11, 2005
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I was just cleaning up my motor (1979 I6 90HP), when I noticed what appears to be a leak from the gasket between the crankcase and the intake manifold. Everything looks more nasty in the pic than it does in reality, I could just make out deposits of gummed up 2 stroke oil - leaking fuel/air?<br /><br />
LeakM.jpg
<br /><br />I know that on a 2 stroke, the crankcase sees alternating vacuum and compression, and I'm probably getting a fuel/air leak at the junction between the crankcase and the intake manifold. What I'm wondering, is if I have to pull the entire powerhead to replace the gasket? I'm supposed to be going on a vacation in a week and a half, so I'd rather not if I don't have to. Any suggestions? Can I use epoxy or silicone to temporarily patch the leak until I can get it apart to fix it right? Thanks.
 

ZmOz

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Re: Crankcase Gasket Leak? [Pic]

I don't think there is a gasket there at all...it's just a very precise machined fit. That's why you can't replace that peice with one from another motor, it will never fit right. I have no idea why it would be leaking, but yes, if you have to take it apart you'd have to take off the powerhead. I would think epoxy of some sort would make a good temporary fix, but I don't know...
 

79 Silverline

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Re: Crankcase Gasket Leak? [Pic]

Dunno, it looks like there's a gasket of some sort in there, but it could be paint peeling back giving the illusion of a gasket being in there.<br /><br />Didn't I read that you just rebuilt an I6? How much of a PITA would it be to remove, reseal and reinstall the intake manifold onto the motor? I'm trying to figure out how bad it'll be if worst comes to worst.
 

ZmOz

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Re: Crankcase Gasket Leak? [Pic]

I didn't rebuild mine, but I replaced the powerhead and took apart the old one. To reseal that, you'd need to remove all the cowling, unbolt the powerhead and some things attached to it, lift it off, unbolt the top of the crankcase, do whatever needs to be done to seal it, and reverse the process. Not very difficult, but time consuming...
 

Chris1956

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Re: Crankcase Gasket Leak? [Pic]

Silverline, There is a rubber gasket that fits into a groove in the crankase cover or block (I forget which). It is cheap to replace, but the labor necessary to pull the powerhead and remove the crankcase cover is quite a bit. I would check the bolts on the crankcase to make sure they are torqued properly. The specification is 200 inch pounds of torque. Maybe they vibrated loose. If that is not the issue, maybe you could clean up the area and apply some liquid neopreme or auto silicone to the joint
 

79 Silverline

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Re: Crankcase Gasket Leak? [Pic]

Yeah, upon reinspection this afternoon, there is no gasket between the two! But there appears to be a groove of some form - that must be where that gasket is. 200 inch pounds, you say? Thanks, I'll put the torque wrench on it and make sure they're to spec.<br /><br />I'll try to patch it (for now) if that doesn't do it. Question? Is that part only sealed off from the outside, or will patching it over not stop it from leaking internally as well? I've never had an outboard apart, so I dunno what's behind the leaking area. Thanks!
 

jheron

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Jul 21, 2004
Messages
284
Re: Crankcase Gasket Leak? [Pic]

There is a cork gasket between the 2 halves. I would not try and "patch it up" if its running fine just leave it until you can pull her apart. You can spray some wd40 on the area when it's idling, if it revs up than the leak is substantial and should be repaired ASAP. <br />Jon
 

JasonJ

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Aug 20, 2001
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4,163
Re: Crankcase Gasket Leak? [Pic]

I had a 1963 85 horse inline 6 that seeped the entire seam. It made things a bit messy. My solution was to pull the powerhead and seperate the halves. I cleaned the surfaces, and use an extremely thin coat of high temp orange rtv. We are talking really thin. Reassembled, the motor never seaped again, and ran just fine. There is some goo they use at the factory to accomplish the seal from what I was told, so I theorized that scraping the hardened goo off, and using the skimcoat of rtv would not make things worse. The whole process took about a day, it was not nearly as hard as it may seem.
 

79 Silverline

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Re: Crankcase Gasket Leak? [Pic]

Cool, thanks guys. Since I'm going on vacation with the boat on the 12th, I'm trying to avoid pulling the powerhead (for fear of not getting it back together in time). I cleaned the area with acetone, and then smeared a thin layer of Marinetex into the joint. It should be tough enough to seal against vacuum, compression, and fuel/oil long enough to get me through my trip on the 12th. When I have time, I'll pull the powerhead and do the job right.<br /><br />Jason - so you say it's not too bad huh? I think when I get some time, I'll try to do exactly what you did and fix it correctly. Good to know that it can be done in a day, thanks.
 
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