Checklist for troubleshooting shifting and noise issues? [1990 3.0L OMC Cobra I/O]

[JoeDirtPharmD]

Greets!

1990 Donzi with 3.0L OMC Cobra I/O (MED series). Still waiting for my service manual to arrive.. *sigh*

We were successful in getting the motor to fire/idle great after Pertronix install and carb rebuild. Also changed motor and stern drive oil (per appropriate procedure outlined on forum).

Lower housing has part of the fin broken off, and the prop is chewed up - no history on how/when. But, it's obvious it hit something in it's past

Starting it is a bit of an art, need to jiggle the throttle just right to catch it in neutral. When we were adjusting idle, there was a point where there was an abrupt, repetitive clunking noise (like a brick in a clothes dryer ) coming from the drive. Immediately turned it off.

Upon restart, it made the same noise. I engaged the red tab on the throttle and jiggled the handle and it went away.

Drive shifts fine into reverse, prop shaft spins. No love from the forward gear, however. We're wondering what to look for in stepwise fashion, and if that includes performing the shift adjust per Stuart's site? The cable is red, so I'm assuming that's the updated one...

Anyone wish to share their opinion, good, bad or otherwise on what I'm looking at? Seemed that it was trying to engage during idle... not sure if the drive is shot or in need of repair? Checklist of things to look at? We're VERY new at this, so definitely a learning curve to overcome here.

Any tips, hints or suggestions would be appreciated.

SUMMARY:

• 1990 OMC Cobra I/O (MED series)
• Motor is good, idles/revs fine
• Prop is chewed up, lower fin on lower unit is partially gone. Prev. history unknown.
• Drive shifts into reverse, not forward. Finding neutral is a bit finicky
• Make horrific cllunking noise during idle as if it were attempting to engage
• Have red cable installed
• Pertronix installed, have not installed the ESA fix
• Stern drive oil changed per manual, came out dark and some metallic residue, but no chunks.
• In need of a troubleshooting algorithm, things to look for, etc.

 

[JoeDirtPharmD]

Re: Checklist for troubleshooting shifting and noise issues? [1990 3.0L OMC Cobra I/

To my untrained eye, the cables are working, but no go at least going forward Some pictures to demonstrate:

FORWARD position

NEUTRAL position

REVERSE position

Stern drive

 

[sea wolf]

Re: Checklist for troubleshooting shifting and noise issues? [1990 3.0L OMC Cobra I/

The bottom line is that you will have to go thru the steps outlined in Stuart's site, including pulling the drive, splitting it & checking the height of the shift rod. There ain't no shortcuts. You should be pulling the drive anyway to check the u-joints, gimbal bearing & bellows. From the looks of that drive, it didn't much p.m. It took quite a hit. Make sure there's no oil leaking past the prop shaft seal. You may be able to fix the fin with a skeg guard. Not sure about that though. There ain't much left to it. Good luck.

 

[Lou C]

Re: Checklist for troubleshooting shifting and noise issues? [1990 3.0L OMC Cobra I/

I agree with seawolf, the drive has to come off so you can check the adjustments the right way, starting at the shift rod height, the bellcrank and shift cable. Also even though the shift cable is the red one it could still be bad, with too much drag causing shifting problems. Finally you have to add the circuit to the Petronix to have the ESA work, the ESA lets it idle slower when shifting out of gear, if the ESA does not work you will have shifting problems no matter what you do. I kept the points in mine just to avoid dealing with that. Simpler just to replace points when they need it.

 

[JoeDirtPharmD]

Re: Checklist for troubleshooting shifting and noise issues? [1990 3.0L OMC Cobra I/

Sure thing! Going through Stuart's guidelines won't be an issue.

Was just hoping to get some insight/opinions on the noise issue and whether anyone thought this may be a matter of the drive cable being out of adjustment.

 

[sea wolf]

Re: Checklist for troubleshooting shifting and noise issues? [1990 3.0L OMC Cobra I/

Sure thing! Going through Stuart's guidelines won't be an issue.

Was just hoping to get some insight/opinions on the noise issue and whether anyone thought this may be a matter of the drive cable being out of adjustment.

Yep. Hopefully, that's all it is.

 

[JoeDirtPharmD]

Re: Checklist for troubleshooting shifting and noise issues? [1990 3.0L OMC Cobra I/

As a follow up/resolution: ended up splitting the drives - shift rod was bent. Removed prop shaft, a handful of gear teeth feel out on the garage floor. Teeth on forward gear and drive shaft bevel gear were stripped to the nubs.

Picked up a used lower on eBay. After new seals/gaskets, perusing the shop manual (that finally arrived), Stuart's article, and the homebrew ESA interface for the ignition, glad to say the boat runs great! Better than initially expected, really...

Hope to be able to post our restoration thread later this winter