OMC Cobra outdrive noise

[A1957]

i just completed fixing the shift assist system on our 1989 Sanger with a 5.7 liter engine and King Cobra outdrive and went for a short ride. The drive has a tremendous amount of what sounds like gear noise.
The gunnels of the boat are enclosed from just forward of the shifter handle to the stern so it’s like a sound tunnel. The noise is actually louder at the helm then in the open areas of the boat.
The noise gets louder and changes pitch when turned left or right from straight.
My first thought was possible wear in the U-joint/CV assembly so I pulled the outdrive off. They appear to be tight and the splines of the shaft look OK.
What I did notice is the incredible amount of backlash there is when rotating the shaft clockwise-counter clockwise with my hands. I didn’t get a chance to measure it but it’s WAY more than a properly setup ring and pinion assembly in a car which is really my only point of reference. I’ll pull the top cover tomorrow and take a peak.
i did drain the drive before I pulled it and there was very little metal dust on the drain magnet. Otherwise the oil was full and pretty clean.
Any thoughts about how much gear slop I should have?
And would there be any drawbacks to me running the engine with the drive off? I just want to verify that in fact the sound is now gone with the drive off. Maybe 15-20 seconds max.
And finally, how can I shift the drive from neutral to forward or reverse while it’s off the boat? I see the shift shaft. Is it up and down or left-right or ???
Thanks in advance.

 

[HT32BSX115]

You might have a bad gimbal bearing.

No problem running the engine with the drive off. Just disconnect the hose that goes from the transom mount to the T-stat housing (or power steering pump cooler) and hook your water hose up there with some common plumbing fittings.

You don't want to run the engine without cooling water flowing or you will cook the exhaust manifolds, risers, Y-pipe and exhaust shutters. The shutters will melt first!

Find your model number together and get a correct year OEM (OMC) service manual. (NOT Clymer/Seloc)

Also get an alignment tool so you can check it.

I can't remember which way you push (or pull) for FWD or REV....but It should be obvious from moving the shifter with the drive off.

You can move it manually, and turn the input shaft to see what gear you're in.

IN FWD, turning the prop by hand will "ratchet" turning it FWD and "lock" trying to turn it in the REV direction.....and vice versa when shifted to REV.

 

[A1957]

Thanks for the reply.
I have ordered original OMC service and parts manuals. They should both be here Monday so I’m kinda holding off until then. I know most of the part numbers in the parts manual will have been superseded or obsoleted but the exploded views are a big help to me.
I’ll get an alignment tool also. I’ve seen them on eBay relatively inexpensive. If it is the gamble bearing will I need a special tool to remove/replace?
And do you think I’ll be able to hear the bad bearing with the engine running or just wait and check it with the alignment tool?

 

[Lou C]

That does not sound good to me. There is normally very little backlash in the upper gears which is what you are feeling when you turn the driveshaft. There will be drag on it due to the fact that you are also turning the impeller blades when you turn the driveshaft. What is the history of this drive and how exactly was the outdrive oil changed the last time it was done? A properly set up and full of lube Cobra drive is QUIET. Merc boats I've been in are noisier, the Cobra is not.

Have you check the gear oil with the dipstick in the middle of the top cover? Is it full? They take about 2 qts after draining.

https://www.crowleymarine.com/support/tech_articles/omc-cobra-outdrive-lubricant-filling.html

 

[HT32BSX115]

A properly set up and full of lube Cobra drive is QUIET. Merc boats I've been in are noisier, the Cobra is not.

Have you check the gear oil with the dipstick in the middle of the top cover? Is it full? They take about 2 qts after draining.

I was shocked at how much louder my Bravo III is compared to my previously installed King Kobra.....

 

[A1957]

So clarification to my OP. I have the “350 King Cobra” engine/outdrive but it is not the “King Cobra” outdrive. Based on the picture ID page I found, the outdrive is the standard Cobra. The model number of the drive is 985273.
I got to look closer at it this morning and here are my observations:
- I drained the oil prior to removing the drive and the oil was clean and full per the dipstick. I poured it into a 1 gallon jug and it filled almost exactly half way so my take is that the drive was properly filled.
- The bellows for the exhaust is worn through at the bottom of 6-8 convolutions. It must have been leaking exhaust badly.
- The bellows for the driven shaft is probably also bad. It had water in the bottom of it which may have happened when I removed the drive. But...
- The bearing is a rusted mess. It spins quite freely but you can hear the dry, rusted balls or rollers inside. It does not seam to move fore-aft or side to side but is definitely toast.
- I was able to put the drive in gear and rotate it. With the oil reservoir top off I can see that the beveled gears look very good. What I thought was excessive gear slop before must have been while in neutral because there is none now.
- There appears to be a screen inside the four water intake ports on the lower part of the drive but it’s slid up and only covers 1 of the 4 holes. Do have to split the upper/lower drive to fix this?

So my plan of attack is to buy a bearing and seal, a bellows kit, I already have the drive removal gasket/oring kit, I’ll need an oring for the top reservoir cover, washers for the drain and fill plugs and some drive oil. I already have lube for the zerk fittings.
I already ordered the manuals and the alignment tool. What will I need to remove/replace the bearing and seal?

Am I forgetting any parts or tools?

Any tips you can offer me to make this go smoother?

And again, thanks for sharing your knowledge. Otherwise this would be in a shop that I can’t afford.

 

[PITBoat]

https://forums.iboats.com/forum/eng...ines-outdrives/481978-home-made-special-tools

 

[A1957]

Thanks for the link.

 

[Lou C]

That bearing looks like it has not seen grease in years so that is likely the source of the noise.
Glad your drive has 2 qts of oil in or else you'd be looking at a rebuild or used drive
When you do the bellows, you will have to either disconnect the shift cable down at the pivot housing, or, disconnect it up at the engine bracket (this saves you from having to re-adjust it) to allow the cable to move rearward enough to pull the pivot housing out a bit (support it so it does not hang on the shift cable) to replace the bellows.

When you do the bellows, you have to remove the 2 hinge bolts on either side and there is a fiber washer between the pivot housing and the part its bolted to that may fall down, you have to fish them out and make sure they are installed when you put it back together.

The Cobra bellows has a ridge on the gimble housing side that fits into a groove in the gimble housing flange. The hose clamp should be oriented between 1:00-2:00 to not pinch the bellows when you turn. The other end just pops into the end of the pivot housing. The exhaust bellows is supposed to have slits on the bottom to prevent excess back pressure. The driveshaft bellows is aysemmetric, there are 7 folds on the bottom side and 6 on the top, this helps prevent cracking if the boat has to be stored with the drive up for a long time.

I clean up the flange on the gimble housing and put some OMC gasket sealer on it, same thing where the other end pops into the end of the pivot housing. When re-installing the drive, coat that paper gasket on both sides with the same sealer. I like to pack the area where the bellcrank in the pivot housing moves back and forth with OMC triple guard grease, this keeps water out in case the gasket leaks.

 

[A1957]

Interesting about the slits in the exhaust bellows. I thought I had found why the exhaust was louder last year. I’ll have to keep looking because it definitely was.

 

[kenny nunez]

To make it easier to re-install the drive try to have it supported so that you do not have to hold it up while trying to push It into the pivot housing. The top cover dip stick has a 1/2” 13 thread that will hold the drive with a hook or bolt with some chain. Supporting it with a jack is a alternate. The bellows on the pivot side has a close fit where the driveshaft has to pass through, put some grease on the outside of the section where the universal joints are located. While pushing the drive in use a large screwdriver to rotate the shaft which will help get it through.

 

[Lou C]

That's how I do it Kenny, a long very thin screwdriver to get the splines lined up. And using an alignment bar to get the bearing straight is important. When I started doing the drive R+R I built a wood stand then as I got older I treated myself to a drive jack which is much easier.

 

[A1957]

To make it easier to re-install the drive try to have it supported so that you do not have to hold it up while trying to push It into the pivot housing. The top cover dip stick has a 1/2” 13 thread that will hold the drive with a hook or bolt with some chain. Supporting it with a jack is a alternate. The bellows on the pivot side has a close fit where the driveshaft has to pass through, put some grease on the outside of the section where the universal joints are located. While pushing the drive in use a large screwdriver to rotate the shaft which will help get it through.

I used one arm of my 2 post car lift to lift the drive off. I used a 1/2” bolt, a piece of angle and some rope. Worked great.

 

[kenny nunez]

Necessity, the mother of invention! Smart move.
If the local Zoning on garage height was not so strict I definitely would have a lift in my garage.
When you drive in the gimbal bearing be careful not to let the tolerance ring come out between the outer lips of the bearing retainer and get caught in the gimbal housing bearing receiver.

 

[HT32BSX115]

Interesting about the slits in the exhaust bellows. I thought I had found why the exhaust was louder last year. I’ll have to keep looking because it definitely was.

Don't worry too much about the "slits" in the exhaust bellows! My Previous "King" Cobra (also a "regular Cobra") ran with NO exhaust bellows at all! I didn't know it until I looked. it didn't make much difference in running and noise.....

OMC used "King" to name all the Cobras. It's a marketing thing only.

You have a Dog-Clutch Cobra.

The other two Cobras are the Interim Cone Clutch model and the SX model (SX is really the Volvo Penta SX drive)

Be VERY GLAD you do not have an interim Cone Clutch model!!

Just make sure you fill it with oil correctly, and you check the alignment carefully when you put it back together, and when shifting into either FWD or REVERSE, do it briskly.

Don't shift INTO gear slowly. Once adjusted correctly, and taken care of, a "dog" will outlive you!! :thumb:

 

[A1957]

I purchased an alignment tool for the outdrive. Do I also need a shift cable adjustment tool? I’ve seen the two piece tools for sale but my manuals won’t be here until Monday so not sure if I will need them.

 

[Lou C]

If you are going to disconnect the cable at the pivot housing end then yes you need the 2 tools that get it right, there is one that holds the bell crank at a 90* angle and the other that goes up on the engine bracket that sets the length of the cable between the pin on the engine bell crank and the retainer on the load lever (lever that trips the esa). Now I have done the bellows by disconnecting the transom cable up on the engine, and just being careful to pull the retainer out without changing the setting to do the bellows. But if it was not shifting right before, then yes you should do the whole adjustment procedure.
Using the tools greatly increases the probability of a successful outcome. IF you do a search on my user name I have typed out the procedure several times....

 

[HT32BSX115]

Using the tools greatly increases the probability of a successful outcome. IF you do a search on my user name I have typed out the procedure several times....

:thumb: :thumb: