1986 18' Cobalt 5.7 OMC

[midsouthfire]

Bought this project boat a few months back and working to get it right. Paid $300 and after a tune up and carb rebuild seems to run fine, My question is there's silicon around the bolts on the starboard side of the outdrive upper unit. There is also a hole where the water gushes out on the opposite side from the medallion. Has anyone have any answers. Also where can I get a service manual.
The model # is 983844 and serial # is TO442836. Any info would be greatly appreciated.

 

[Bondo]

Re: 1986 18' Cobalt 5.7 OMC

Has anyone have any answers.

Ayuh,......

Welcome Aboard to the forums here at iboats.com......

I don't do OMCs, muchless the old Stringer Drives.......
But,.......
1 of the Guys will be along,+ Give you alittle insight on just What you've got going on.....

 

[gcboat]

Re: 1986 18' Cobalt 5.7 OMC

If it's an OMC unit
DO NOT remove the retaining screw from the port side of the drive. As far as silicone on the bolts there must of been a previous leak of some kind for the PO to do this. The water coming out is due to probably the seal either being worn, the nut needs tightening or a combination of both. Again, there is no reason to remove that screw - there is nothing serviceable there. I have absolutely no idea the purpose of it other than it might either be an inspection port or a cleaning port. If someone knows - please fill me in.

 

[Lou C]

Re: 1986 18' Cobalt 5.7 OMC

A 1986 could well be a Cobra, (don't think Stringers had the Medallion) and if water is gushing out of the side opposite from where the medallion is, I bet someone else removed the screw, or didn't screw it in right....You are not supposed to remove them as noted, and it has to seal off that water passage. You can see the parts needed to fix that if you go to dougrussell.com[/url] look in OMC parts and if you go to the 1992 model year for the Cobra, the parts are listed in the upper unit section. These were all the same, 86-93, but for some reason, these parts were only seen in the 92 and 93 parts diagrams. To properly replace the screw, the drive has to come off, because there is a retainer that fits into the water passage in the upper unit that holds in the screw. If you remove the drive, fix the leak that the previous owner may have tried to fix with silicone.

here's a pic of mine running on the hose, the Cobra has trim rams like the Merc Alpha, the stringers do not.

 

[midsouthfire]

Re: 1986 18' Cobalt 5.7 OMC

It is a Cobra outdrive not a stringer, the silicone is where the outdrive bolts to the transom assembly. Has anybody come up with another answer to fix the hole in the outdrive other than removing it and replace the plug? What was it for?

 

[Lou C]

Re: 1986 18' Cobalt 5.7 OMC

I don't know if a plug could be used there, because of the water pressure behind it, but you have to remove it anyway, to get rid of the silicone and replace the gasket (coated with OMC gasket sealer or perfect seal) the right way. I'd just order up the parts if doug russell has em and do it the right way.

 

[midsouthfire]

Re: 1986 18' Cobalt 5.7 OMC

I appreciate it, is there anything else I need to look out for?

 

[Lou C]

Re: 1986 18' Cobalt 5.7 OMC

Two things about the Cobra that you have to watch out for:

draining and refilling the drive must be done the 'OMC WAY' not the Merc way, do a search on this forum, I've posted the instructions a couple of times, they take 64 oz of gear oil. If you do it wrong you will burn out the upper gears and need a rebuild

the transom shift cable, if not adjusted right or corroded and failing, will cause it not to shift into gear all the way, and jump out of gear which will ruin the dog clutch. Also sometimes they won't shift to neutral, you can get the shift into neutral but it can still be in fwd or rev, which is a safety risk. Do an internet search for the Stuart Hastings OMC Cobra site, that will tell you all you need to know about the shifting issue.

Once they are set up right they are a pretty good drive, I had a good OMC tech set mine up a few years back and all it has needed was regular maintenance since.

 

[midsouthfire]

Re: 1986 18' Cobalt 5.7 OMC

Can you guys tell me where to get the shop manual for the cobra outdrive, they are pretty pricey on ebay. thanks

 

[Coors]

Re: 1986 18' Cobalt 5.7 OMC

ebay, seamanray13.
and he ain't cheap, but has them. bite the bullet.

 

[Don S]

Re: 1986 18' Cobalt 5.7 OMC

The sterndrive section of OMC went out of buisness about 10 years ago. Don't expect anything to be "Cheap"

 

[flabum]

Re: 1986 18' Cobalt 5.7 OMC

As for that plug on the side where water is "gushing" out. You can either try to find all the parts need or take it to a welder and weld a plug ove the hole. Your choice.

 

[midsouthfire]

Re: 1986 18' Cobalt 5.7 OMC

Is the hole on the port side for flushing the outdrive or draining it? I would rather just weld it up and be done with it, just don't want to do it if it serves a purpose .

 

[Don S]

Re: 1986 18' Cobalt 5.7 OMC

You still need to pull the drive and get that plate that fell off out of there, so you might as well fix it right. My guess is that plate prevents errosion of the aluminum housing where the water changes direction, but who knows for sure.

 

[Lou C]

Re: 1986 18' Cobalt 5.7 OMC

Another one of those mysteries. The Doug Russell site shows those parts as still available, so get em while you can!

 

[midsouthfire]

Re: 1986 18' Cobalt 5.7 OMC

I'm gonna order the manual to find out how to do it right. Is there anything to watch out for before/when I pull the outdrive off?

 

[Lou C]

Re: 1986 18' Cobalt 5.7 OMC

If you go onto Crowley Marine, on the site they have instructions for removing the drive, it's actually pretty easy:
put shift in Neutral
get a block of wood to support the skeg, or build a stand if you don't want to throw your back out (I built the stand!)
remove the nuts holding the rams, slide out the rod (you may have to tap it thru...I used a small 1/4in extension to do that)
Remove the six nuts that hold the drive on
You may now have to wiggle and pull on it to break the seal, but it should come off, support the driveshaft as it comes out so it doesn't bang on the anode on the front of the drive....Keep in mind, it is HEAVY, be careful!
after you remove it, put the rod for the trim rams thru the rams, replace the nuts and spacers, and tie it up so they are not hanging down against the trim lines.
Then you have to check the U-Joint bellows for water, or gear oil. Grease in there is ok because it's from the gimble bearing, but water means you have to replace the bellows and maybe the gimble and the u-joints. The gimble should rotate smoothly, if it's rough you need to replace it.

 

[midsouthfire]

Re: 1986 18' Cobalt 5.7 OMC

Thats a neat stand, I would have someone else do it but I hate when someone else works on my stuff......thanks

 

[Coors]

Re: 1986 18' Cobalt 5.7 OMC

That mystery plate retainer is down in the bottom of your drive. You need to get it out, as it might clog a water passage.
Then modify it so that you, or anybody else doesn't un-screw it anymore.

 

[midsouthfire]

Re: 1986 18' Cobalt 5.7 OMC

I think i'm gonna weld a plug over it so there won't be anymore "problems" after I remove the drive and get the plate out