OMC Cobra 5.0 broken ???

[Chris Martin]

Hey guys hope you can help. I have a 1991 VIP Kona with a 5.0 OMC Cobra. I was running it this weekend and all was well. I was running around 55-60 mph, at about 4500 rpm. When I got out of the throttle, I heard a gnawing sound coming from the out-drive. I shifted into neutral, and the sound continued. I killed the engine and pulled it to shore. With the boat trailer-ed and in gear when you turn the prop you could feel it slip over the gears. I have since pulled the out-drive, and separated the upper and lower unit. It had plenty of fluid in the unit. There were some small metal flakes found in the fluid. The upper gears and bearings appear to be fine. I am thinking that the lower unit gears have come apart. Is there anyway to inspect the lower gear unit? I have had the boat about 3 years now and it has never gone in to reverse, could this be part of the problem? I understand engines, but the out-drive is all Greek to me. Any help will be greatly appreciated. I have never seen a boat like this one, and really don't want to scrap it and start over, but I don't want to spend more than it is worth to repair it.

 

[HT32BSX115]

Re: OMC Cobra 5.0 broken ???

Howdy,

Welcome aboard!

When I got out of the throttle, I heard a gnawing sound coming from the out-drive. I shifted into neutral, and the sound continued.

Any number of things can cause this but most of the time it's a gimbal bearing and/or u-joint problem.... If the noise changes when you turn turn the steering wheel left and right it usually confirms the bearing and U-joints. Removing the drive gives you a first-hand look at them...

With the boat trailer-ed and in gear when you turn the prop you could feel it slip over the gears.

You're talking about turning the prop "FORWARD" with the drive in FWD and it "clicked"?

Perfectly NORMAL. They all do that. (clutch dogs slipping)

I have since pulled the out-drive, and separated the upper and lower unit. It had plenty of fluid in the unit. There were some small metal flakes found in the fluid. The upper gears and bearings appear to be fine. I am thinking that the lower unit gears have come apart.

While it might be "normal" to see *some* metal in the oil, you wouldn't want to see a LOT unless the oil hasn't been changed in many years. I wouldn't want to see ANY if I had just run the drive after an oil change. When did you change the oil last?

Is there anyway to inspect the lower gear unit?

Disassembly. But if you do that without the proper tools, OEM service manual and the "skills", you may be buying yourself a rebuild.

I have had the boat about 3 years now and it has never gone in to reverse

Because you just don't use Reverse or it WON'T go into reverse?

If it will NOT go into reverse, you could have a drive problem and/or lower shift cable problem. either of those could damage the clutch-dogs eventually.

 

[Chris Martin]

Re: OMC Cobra 5.0 broken ???

I have removed the drive and inspected the U joints and bearings, they appear to be fine.

As for the prop slipping, I had the drive in forward, and could feel it slip while turning the prop in reverse. When turning the prop forward there is no resistance at all.

It has been about 18 months since the fluid was changed and there was just a small amount of flake in the fluid.

The boat wouldn't go into reverse, not that i didn't try. I suspect that the linkage at the carb. was not set properly. I haven't used the boat in quite a while. I work overseas and didn't get to use it but one time last summer.

I have the unit pulled apart at this time. I have a feeling that the lower unit is going to need a rebuild now no matter what I do. The sound that came from the out drive was very loud and sounded very expensive when it happened. How can I inspect the lower gears?

 

[Levinz11]

Re: OMC Cobra 5.0 broken ???

Good luck getting her fixed. That is a sexy looking ride!

 

[HT32BSX115]

Re: OMC Cobra 5.0 broken ???

As for the prop slipping, I had the drive in forward, and could feel it slip while turning the prop in reverse. When turning the prop forward there is no resistance at all.

Well, that is quite different.

If you can turn the prop [backwards] with the drive in FWD, (and it's really IN gear) You have an internal problem with the shift dogs. (I.E. they're "toast")

If the drive will not shift properly into and/or out of either gear, it indicates a possible problem with the lower shift cable (a common Cobra problem)

Running it that way can and frequently DOES damage the drive.

Sounds like a rebuild but you won't know until it's apart.

Understand that BOTH the upper and LOWER must be disassembled since there'll be metal contaminated oil in both.

That boat is pretty cool.

If I had it I would consider finding a complete Mercruiser Engine and drive to replace the OMC "stuff".
(About 5 years ago I removed the complete OMC 460 King Cobra from my 1987 FourWinns 211 Liberator and replaced it with a 1997 Mercruiser 454+ Bravo III I bought off Craigslist from a boat that had a tree fall on it!)

Since Cobras are not cheap to rebuild and OMC is no longer in business, this would be a good time to consider doing the above, or replacing the drive with an SEI drive.

http://www.sterndrive.cc/mm5/merchant.mvc?Screen=CTGY&Store_Code=SE&Category_Code=Cobra



I would not put major money in any Cobra.

Sorry about that,


Rick

 

[Chris Martin]

Re: OMC Cobra 5.0 broken ???

Well she's toast. I drained the fluid and pulled the upper and lower apart, major metal chunks found in the lower unit, upper gears and bearings appear to be in good shape. I think that the lower unit has eaten itself up. I think that I will take your advise and try to change out the entire setup.

 

[HT32BSX115]

Re: OMC Cobra 5.0 broken ???

Well she's toast. I drained the fluid and pulled the upper and lower apart, major metal chunks found in the lower unit, upper gears and bearings appear to be in good shape. I think that the lower unit has eaten itself up. I think that I will take your advise and try to change out the entire setup.

Yeah, bummer!

Look for a damaged boat you can buy with an otherwise intact Mercruiser (or Volvo!) engine and drive. OR a similar boat that has a freeze damaged engine similar to yours.

You can then remove the freeze damaged engine and drive, and yours, strip your engine down to the "long" block and install the "new" transom shield/gimbal mount, your engine with all the Mercruiser or Volvo trimmings and the "new" drive.

Choose as new as you can find. I would want a Mercruiser Alpha GEN II (or a Volvo Penta SX) type drive and associated engine.

I am not all that familiar with Volvo other than you want a Volvo that is approx newer than about 1995/96 or so (when ever the SX came out)

If Mercruiser, somewhere around 1992 or 93 I think.......

When I did my OMC--->Mercruiser swap out, I looked for BOTH in a (300hp+) 350MPI/ 454/496/502 + associated drive and found SEVERAL Mercruiser engines and drives locally (Seattle/Western Wa) I didn't find ANY complete Volvo packages

I tended to lean toward Mercruiser because there seemed to be a far greater supply of used parts available everywhere.
(do a search on EBAY in "boat parts" for "Mercruiser" and "Volvo" and you'll find about 3 to 4 TIMES MORE Mercruiser "stuff" than Volvo)


It might be cheaper in the long run to do an SEI conversion using their $350 "kit" and a new warranteed drive. There's several people that here that have done that.

You could also just buy another rebuilt or used drive. I could have stayed with the King Kobra when I had it, but I'm glad I did the switch!


Regards,


Rick

 

[Chris Martin]

Re: OMC Cobra 5.0 broken ???

Rick, Thanks for all of your help. I'm going to order the SEI conversion and the new drive. I would rather do that than buy a used Cobra and risk it being bad, or going bad again. I looked at the instructions, it doesn't look like it will be too difficult to install. I'm going to order it next week, and hopefully be back on the lake in a few weekends. Thanks again.

 

[HT32BSX115]

Re: OMC Cobra 5.0 broken ???

Rick, Thanks for all of your help. I'm going to order the SEI conversion and the new drive. I would rather do that than buy a used Cobra and risk it being bad, or going bad again. I looked at the instructions, it doesn't look like it will be too difficult to install. I'm going to order it next week, and hopefully be back on the lake in a few weekends. Thanks again.

There's more than a few people here on iBoats that have done this conversion so do a search.

You can probably avoid most of the pitfalls etc...

They have a pretty good product and I hear their support is excellent.

You probably already found their forum http://sterndrive.cc/vbforum/forum.php

Good luck!


Rick