1987 OMC Cobra 5.0 Re-Build

[kylejb2663]

Hey Guys,

So I winterized the boat and from what it looks like there is not a ton of flow of water which I am assuming may be because the Impellers have not been changed in a while- 3 Years since I last saw a receipt for it. Granted the engines ran great this year but it's time to replace them.

However, here is my problem, Port side stern drive looked milky...... Not good!!! I want to tackle this myself and learn how to do it. Can iBoats help me?!?!?! I was thinking about starting it mid October when I have some free time. I am guessing a re-seal is in order for the drive? I did not have it pressure tested yet, I figure if I am going in, I'm going to do everything while I am in there. Other drive was re-built about 4 years ago.

Help me iboats! Any tools I need? What are the steps??

I figure I would do a whole service transom kit on both drives as well.

 

[proshadetree]

Re: 1987 OMC Cobra 5.0 Re-Build

Cobras water pump impellers are easy maybe 5 bolts and done. Heck I have done them underwater. Drive reseal wow. Get the drive pressurized and see if it has a leak. If yes I would have a pro build it. Not a job for a average mechanic.

 

[bruceb58]

Re: 1987 OMC Cobra 5.0 Re-Build

When was the last time you pulled the drives? If the u-joint boot has water in it, the water can get in your drive that way as well.

 

[kylejb2663]

Re: 1987 OMC Cobra 5.0 Re-Build

When was the last time you pulled the drives? If the u-joint boot has water in it, the water can get in your drive that way as well.

To be honest, I can't tell you when the last time the drive was pulled. I just purchased the boat this season, I know that I will in fact be pulling both of them in a few weeks.

My Marine Shop quoted me out $1150 to do a re-seal only on the drive. I'm certainly not willing to pay that much money to a mechanic otherwise I would go by a SEI Conversion Kit with a SEI 116 drive and eventually buy another one for the other side. I think I can do the drive re-seal but I need help from iBoats!!

What in particular should I be checking once I pull the drive? Regardless of the condition, I plan on replacing the Gimbal Bearing, Outdrive Seal, Exhaust Bellow, Shifter Cable Bellow, and U-Joint Bellow on each drive.

 

[bruceb58]

Re: 1987 OMC Cobra 5.0 Re-Build

The shifter cable bellow is a tiny boot up inside the boat. No need to change that.

 

[Lou C]

Re: 1987 OMC Cobra 5.0 Re-Build

There are some seals that can be changed with out special tools, such as the seal under shift rod cover, the seal under the water inlet cover, the big o-ring under the top cover and the orings on the bearing housing but other seals require a mechanic and special tools. I'd rig up something to pressure test it and check yourself. Could be something simple like the fiber washers for the drain n fill plugs...Find out first where you think it's leaking and then decide. I would not be in such a rush to convert to an Alpha. The Cobra is a good drive as along as you can get the parts,and have a good tech to fix things you can't fix yourself. I have mixed things about the SEI drives, the conversion is a good idea, but a proper set up Cobra is just fine too....

The impellers are very easy to change, like a 15 min job, it's under the plastic cover on the rear of the upper gear housing. There is a seal on the impeller drive shaft that can leak, that might be your problem, this I'm not sure how hard it is to replace but it had to be replaced on mine, along with the gasket for the bearing housing in the lower unit. After that (6 years ago) no leaks.

 

[LAC_STS]

Re: 1987 OMC Cobra 5.0 Re-Build

If you take the prop off and look in the cavity (inside the bullet looking part) you can see 4 screws. these screws have a rubber seal on each one. These were where my drive was leaking from. And from what I read it is a very common place especially if your prop shaft is out any (tolerance is 2 or 3 thou I think).

You can order new screws that come with the seal on each one if they are leaking. No special tools required either.

But as others have said you should go to a hardware/home improvement store and rig yourself up a pressure tester. You can use the fitting that comes on a gear lube fill if you cant find the right size elsewhere. Many threads on this here. There is no way to tell where your at or what is required until you do the pressure test.

 

[kylejb2663]

Re: 1987 OMC Cobra 5.0 Re-Build

This sounds great guys- Thank you for the advice!!

I will go ahead and rig up a pressure tester and try it out. I'll post in a few weeks on what my findings are! Thanks again guys!

 

[kylejb2663]

Re: 1987 OMC Cobra 5.0 Re-Build

Alright guys- Digging this thread up!

I finally got the stern drives off - built some stands for them as well.

I guess I am just wondering what I should be checking and what the best way is to do a pressure test, I would honestly like to just re-seal them completely. I am not worried about it taking time and it's not like I am in a hurry- I am posting a few pics too of the props. Anyone have any suggestions besides water impellers, gear lube was already changed.

I was planning on doing a full transom kit and gimble bearing, etc. I was also wondering how I could check the U-Joints. I still have one drive on the boat that I have not removed yet so I can do the tests on that if it needs to mounted.

Thanks guys!

 

[kylejb2663]

Re: 1987 OMC Cobra 5.0 Re-Build

Also, here is a pic of the boat too!

Just did a lot of work on the outside of it!!

 

[Lou C]

Re: 1987 OMC Cobra 5.0 Re-Build

that's a great looking boat, I have never seen one of those before, nice!!
Back to the Cobras, was this a salt water boat at one time, looks like it could have been.
Did I see water or gear oil in that bellows? Your driveshaft and u-joints don't look rusted, but you want to check them carefully for wear. If it's gear oil, the input shaft seal on the drive has to be changed. I'd change the driveshaft bellows at least and take a good look at that little water hose when you're in there. The gimble bearing you turn with your fingers and feel for roughness, it should be completely smooth. The u-joints, you feel for looseness and play. While you have got the drives off, clean out the area where the bellcrank is, and then pack that area with OMC/Bombardier triple guard grease, that will keep the shifting from getting stiff. When you reinstall the drives, replace the gasket for the water passage hole on the left side of the pivot housing, and make sure to coat the pivot housing gasket with OMC gasket sealer on both sides. I replace the impeller every other season, it's an easy job on the Cobra, the impeller is under the plastic cover on the upper unit. 3 bolts the cover is off, 3 bolts the impeller housing is off.

You can make up a pressure tester and try to find where it's leaking, but other than the top cover seal, the seal for the shift rod cover and the bearing cover, the other seals need a mechanic because of the need for special tools (esp prop shaft seals and input shaft seal on the upper unit). It's probably worth checking yourself, but I had my drive re-sealed about 6 years ago and it's been fine ever since. I do replace the gaskets for the drain and fill plugs each season.

 

[sam60]

Re: 1987 OMC Cobra 5.0 Re-Build

Very nice looking boat!

 

[Black as]

Re: 1987 OMC Cobra 5.0 Re-Build

That?s a nice looking boat, good luck with the re-build

 

[kylejb2663]

Re: 1987 OMC Cobra 5.0 Re-Build

that's a great looking boat, I have never seen one of those before, nice!!
Back to the Cobras, was this a salt water boat at one time, looks like it could have been.
Did I see water or gear oil in that bellows? Your driveshaft and u-joints don't look rusted, but you want to check them carefully for wear. If it's gear oil, the input shaft seal on the drive has to be changed. I'd change the driveshaft bellows at least and take a good look at that little water hose when you're in there. The gimble bearing you turn with your fingers and feel for roughness, it should be completely smooth. The u-joints, you feel for looseness and play. While you have got the drives off, clean out the area where the bellcrank is, and then pack that area with OMC/Bombardier triple guard grease, that will keep the shifting from getting stiff. When you reinstall the drives, replace the gasket for the water passage hole on the left side of the pivot housing, and make sure to coat the pivot housing gasket with OMC gasket sealer on both sides. I replace the impeller every other season, it's an easy job on the Cobra, the impeller is under the plastic cover on the upper unit. 3 bolts the cover is off, 3 bolts the impeller housing is off.

You can make up a pressure tester and try to find where it's leaking, but other than the top cover seal, the seal for the shift rod cover and the bearing cover, the other seals need a mechanic because of the need for special tools (esp prop shaft seals and input shaft seal on the upper unit). It's probably worth checking yourself, but I had my drive re-sealed about 6 years ago and it's been fine ever since. I do replace the gaskets for the drain and fill plugs each season.

Thanks Lou!! It's a Chris Craft Amerosport 284- looked real different a few months ago before we did all the painting and windows. Swim platform was completely full of rot so I cut open the fiberglass, put new marine grade wood in there, and reglassed it, painted, etc. It's nice and solid now.

I do know for a fact that it has never been in salt water, but the outdrives sure do look like they have been. I would like to re-paint them but someone warned me to be careful because they are aluminum so I was not sure of the process in order to paint them. There was a lot of water in the driveshaft bellows on both sides, so I am wondering if those were the culprit and the drives may not even need to be resealed. The U-joints on the port side had lots of water droplets on them though and tons of condensation- looked more rusted then the one I took pics off.

I do not think that the Fill and Drain plug gaskets have ever been replaced. I did just replace them this year when I winterized it, could that have been the culprit as well of water getting into the drive? Do you by any chance know what special tools I would need? I would almost be willing to buy them because I plan on having this boat for a while- I do know I could convert to a SEI Drive, but there is just something proud to be said that I still have Cobra's that are functioning and maintained!

Water pump does look easy- I purchased the original OMC Workshop Manual, Owners Manual, and Part list and it's detailed in there as well.

Thanks Lou!!!

Very nice looking boat!

Thanks man! It took a lot of time to restore to that compared to what it was, I'll post a before pic

That?s a nice looking boat, good luck with the re-build

Thanks man!!

 

[indybleck]

Re: 1987 OMC Cobra 5.0 Re-Build

Beautiful boat!!!!!!!!!!!!!

 

[Lou C]

Re: 1987 OMC Cobra 5.0 Re-Build

Although you could try replacing the drain n fill gaskets yourself, I still think you want to pressure test it to see if its really leaking. Sometimes if you get water in the bellows, what happens is that water gets in the seal around the input shaft seal which is made to keep oil in but not keep water out (should be though). Start with pressure testing, see what that shows you, replace the bellows on both drives. I'd also start looking around for a good OMC shop, sooner or later you will need one, unless you want to swap both Cobras to Alphas as per SEI's kit. There is also a kit, sold by Volvo dealers and marinepartsexpress.com, that lets you mount a Volvo SX, or DP on a new pivot housing. This is possible because the Volvo SX design, was adapted from the OMC Cobra, during the OMC/Volvo joint venture years. BUT, its way way more expensive than the SEI Alpha swap. Myself, I'd try to find a good OMC shop and have the drives gone through, over the winter. Do the bellows and then make sure you get the shift cables adjusted right. Well maintained Cobras are very good drives, I have one that's 24 years old and it's still going strong. The last time it was in the shop for drive work (re-sealing) was 6 years ago. All I do is change the oil each season, check everything, lube up the shift linkage and it shifts great. It still has the same shift cable on it, as when I bought it 9 years ago, that cable is well over 10 years old.

 

[kylejb2663]

Re: 1987 OMC Cobra 5.0 Re-Build

Alright guys well I finally got the pressure tester rigged and it turns out I am leaking at the input shaft seal and down near the prop area!! I did a measurement though on the prop shaft and it looks like the shaft is even so it must just be the seal, THANKFULLY!

I may have found a guy that will re-build the drives for me. Maybe this is a bit over my head so I'll leave it to a pro, plus I priced out the tools and the guy who is going to rebuild said it would take years to pay off the cost of the tools compared to what he is going to charge me. So maybe that means he will give me a good deal!!!

Quick question, I noticed that when I was trying to get the drives off the transom, they would move side to side like they had a lot of play in them... I don't believe they are supposed to have that much play, correct? How do I fix this? I think I am going to replace the Gimbal and U-Joints just for safety anyways, I really don't know everything that's been done so better safe then sorry, Cheap insurance!

 

[kylejb2663]

Re: 1987 OMC Cobra 5.0 Re-Build

Bumpty Bump... on the post above!

Also, FYI I ordered all the parts hopefully I got the right ones as per the workshop manual... I did not go with Sierra parts I went with Johnson Evinrude OMC OEM Parts- I have heard a lot of people say when it comes to seals that the OEM's are better... not sure-

Upper Seal Kit - 987603
Lower Seal Kit - 0439967
Fill Plug - 0307551
Drain Plug - 0318544
Washers for Drain and Fill Plugs - 0311598

 

[bruceb58]

Re: 1987 OMC Cobra 5.0 Re-Build

You also want the o-ring for the dipstick, oblong o-ring for the water passage and the gasket for when you mount the drive back up to the pivot housing.

 

[kylejb2663]

Re: 1987 OMC Cobra 5.0 Re-Build

bruceb

Sounds good! I'll get those ordered. I was going to order the entire transom kit for each drive that way I can replace all the bellows and make sure everything is up to par. The oblong o-ring for the water passage would you happen to have a part number on that? I did find the one for the dip stick though.

Any ideas on what i should be changing since the drive moves side to side? I was going to do the Gimbal and u-joints as well.

Thanks!