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OMC cobra gearcase plug needed

J

jlbronk

New member
Anyone know what the part number is for the plug that goes in the hole in the attached picture? It is a 1989 OMC cobra upper gearcase and the hole is on the port side, looks threaded and 1 inch diameter.
 

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not normally threaded. someone has threaded it because they made the mistake of removing the plug there and the nut fell down inside the casing.

So you are on your own for a plug. measure and head for the hardware store. or, remove the drive, fish the lost nut out and install the proper plug.
Seeing as the makeshift one is missing, maybe threading it didn't work out so well.

shop.evinrude.com for a parts breakdown and numbers, but all it shows is the decal that is supposed to hide it
0911848 MEDALLION, OMC Cobra 2 $15.76 CAD

no number for the plug hardware
 
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You can also use a rubber plug of the type a lot of boats use to plug transom drain hole under outdrive. It fits perfectly and tightens up very nicely!
 
We tried a rubber gromet but lost that on the first spin on the lake. How does the the rubber plug you are talking of, tighen up?

Also what is that hole in the housing for?
 
I found a local marina that has all the original parts to fix it correctly but it looks like a lot of labor to take the housing apart. They thought it would be necessary to do it that way to remove any 'lost' parts that may damage the inside somehow. Do you think that is necessary?

They did also have a plug like the one that you sent a picture of...looks a lot more simple and fast.

Any recommendations?
 
When whoever took the original bolt off ( thinking it was where you check the oil ) The nut that was on the inside went somewhere. ( droped down where all the gears are ) I would like to have that taken out. Don't you think that would be a good thing to do.
 
Here is a pic of the parts you would normally have there

9 O-Ring 314491
10 O-Ring 307450
11 Plug 912314
12 Washer 912315
13 Nut Plate 912316
14 Screw 912349
58 Cobra Medallion 911839





convert-1.jpg
 
Thanks for the part details...I was finally able to find that info yesterday. At first anything I looked at just at the medallion shown and I knew there was more to it.

How much is involved in opening up the gearcase to fish out the parts and then put it back the correct way?

Looks like i would need to remove the trim arm (anything special needed there?), then remove the 6 bolts and then slide the housing off. Is there anything more to it than that? I will probably replace the gasket since i am opening it up.
 
wizard said:
. ( droped down where all the gears are )
Click to expand...

there's no gears there

that hole goes into the exhaust housing, not the gearcase.

to retrieve,

remove drive

invert

shake

it's like getting a lost pick out of an acoustic guitar
 
A little magnet on the end of a coat hanger wire would be my first attempt. The case is non magnetic, so the part that's inside should stick to the magnet.
 
to remove the drive is it more than removing the trim arm, the 6 bolts and then sliding it off? do i need any special tools?

if the parts went into the exhaust area, then could they have gotten out of the motor already?

can you tell that I have not done this before? :)
 
actually removing the drive is easy as long as it's been removed and re-installed regularly...but getting it back on can be a bit of a struggle trying to keep the ujoints lined up...once you get the retainer plate out (should not be hard) and get it all back together its not really a hard job. You have to remove the drive once a season anyway to check the bellows for water and grease the driveshaft splines and ujoints...part of regular sterndrive maintenance. If these things are neglected then you can have big problems...

BTW when reinstalling you do need a new gasket for the pivot housing...o-rings for the driveshaft and the water hose gasket...check this link for instructions...

http://support.crowleymarine.com/entries/113074-omc-cobra-complete-outdrive-removal

http://support.crowleymarine.com/entries/114108-omc-cobra-complete-outdrive-installation
 
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I have the same problem with a 1989 OMC Cobra 4.3 L I just bought. There is a hole with no obvious purpose, possibly threaded.
One thread says this is not a gearcase plug, but the exhaust housing. Question: Does the rubber plug idea work ? And what happens if the hole is not plugged ?

Abel Hart
10/17/2011
 
I did this earlier this fall. I ended up taking the lower unit off and tried to shake the retainer nut out and couldn't get it. So took it and the boat to a marina that use to sell OMC's and still has a mechanic that knows how to work on them. He had the lower split and the parts out and back together and the back on the boat in a hour. That was changing the lube in the lower also, cost me $165.00. That's a mistake that I won't do again. Some think that port is something that the factory used for pressure testing.
 
I can add this: If you use the boat without that port covered you'll loose most of your cooling water pressure. Mine fell out while on the water. Turned off the engine when it was at 250 degrees. A few more minutes and I would have needed a new engine. I jammed a threaded plumping cap in there and enjoyed the rest of the day. I'm working on something better. Might weld a small plate on it.
 
It was suggested to me to put JB weld over the screw and then sand it and paint it, I should have told the marina to lock tite it in.
 
Just to update people on what I ended up using. This is a rubber and brass expansion plug that I found at my local Ace Hardware. I think mine was 1" but I'm not positive. Fit in perfectly and I'm confident it will stay for a long time. An almost free fix. Note: In my case I'm not concerned with the old parts that might be down in the water section of my out-drive. This is the second fix for this hole and whatever is down there has been happily down there for many years.
plug.jpg
 
Hi guys new to this have a couple questions

I just bought a 1988 grew bowrider got it all started up ran amazing when a friend noticed I have was missing a plug after some research I realized this is the never remove bolt

I'm wondering do I have to fish out that rectangular backing plate thing can I just leave it in there and use a rubber plug to seal up the whole

Can it damage something by just leaving it in ?

All help is appreciated

Thanks
 
Kinmount said:
Hi guys new to this have a couple questions

I just bought a 1988 grew bowrider got it all started up ran amazing when a friend noticed I have was missing a plug after some research I realized this is the never remove bolt

I'm wondering do I have to fish out that rectangular backing plate thing can I just leave it in there and use a rubber plug to seal up the whole

Can it damage something by just leaving it in ?

All help is appreciated

Thanks
Click to expand...
I just ended up in this exact situation. Did you end up leaving it in or getting it out ?
 
You REALLY should get it out, you don't want a piece of steel rattling around in there in your cooling water passage! Restrictions in the cooling water flow in an I/O is what causes problems with overheating that can be hard to track down. Pull the drive and fix it right.
 
Lost my omc medallion in the water resulted in lost of cooling water and as result overheating motor and coolingwater leaking in the cylinders and rost. Ended with new motorblock.
 
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