1986 OMC Cobra 4.3 V6 no longer engages forward or reverse

Hello gang, I'm new here on this forum and seeking some help with my I/O drive. I have a 1986 OMC cobra stern drive I guess is what its called. It's a 4.3 V6 and we have owned it a couple seasons. It has always performed well and I have had no issues with it. This last outing however, we had been boating all morning - then parking it in a cove to meet with some friends and anchored for awhile. Some other friends came by on their boat and we stated up to follow them to another cove to hang out with them. We followed them for about a mile or two (moving at 25-30 mph) and all seemed normal with the boat and how it was running. The water was a little rough and I had been following them on the their side so inadvertantly riding in their wake. It was too rough so I slowed to idle and was going to pull in directly behind them. I came to a stop, then it happened, the prop would no longer engage. The engine was running normally and revved up when I tried to engage the prop, but the prop wouldn't spin in either forward or reverse. It sounded just like I was revving it in neutral like when I pull the lever out and push it forward, like to give it more gas when I am starting it. Anyway, engine runs normally, it revs when I move throttle, just prop will no longer engage. I have not experienced any problems with this engine prior to this. It was just that sudden, I came to a rest while being propelled along, tried to start moving again, and prop doesn't engage.

How do I proceed to diagnose this? I have so far found the cable that goes to the engine, and when I push the button on the throttle lever "up" like normal and push the throttle forward or reverse, the part that the cable is mounted to moves, and a little triangular gear looking thing moves also, and a little switch that is attached to a bracket is engaged when the gear thing moves up or down (fwd or reverse). What else am I looking for?

Thanks for any help.

Jerry Romero, wichita, ks

Re: 1986 OMC Cobra 4.3 V6 no longer engages forward or reverse

Howdy,


Welcome aboard!


It sounds like you may have had a coupler failure, a prop hub failure or a drive failure.........

You can tell by looking behind the engine with the engine running. Does the drive shaft turn? You might need a flashlight. Also, if the coupler has failed, running the engine very long will cause an overheat since the raw water pump is not turning. You'll know because the risers will get hot pretty quickly.

If the drive shaft does turn, then (on the trailer) put it in gear with the engine off, and have a look at the prop. Can you turn the prop (by hand with the engine OFF) with the drive in gear? If you're in FWD, there should be a "clicking" sound when you turn the prop forward (clockwise) and you should not be able to turn the prop CCW. (opposite for REV)..........

You may have a "spun" prop hub. It'll be fairly obvious if that's the case. If you suspect a spun prop, try a different prop.

If none of the above has happened, you may have had an internal failure in the drive unless your lower shift cable miraculously failed in neutral.

Sorry about that,


Rick

Re: 1986 OMC Cobra 4.3 V6 no longer engages forward or reverse

Rick, thanks for those diagnostic tips. I will try them later today and report back. Thanks allot for your help!

Jerry

Re: 1986 OMC Cobra 4.3 V6 no longer engages forward or reverse

OK, I just got done diagnosing as Bryan suggested. Here is what I found:

1. With engine running, the drive shaft is spinning happily, I can see it spinning.
2. Boat on trailer with engine OFF and trimmed down -

I placed the drive in Nuetral - the prop spins freely in either direction with no resistance.

With drive in FWD - prop has heavy resistance and I can spin prop CCW and CW

With drive in REV - prop has heavy resistance and I can not spin the prop in either direction.

What does all this tell me, and is there anything to check next?

Thank you for your help.

Jerry

Re: 1986 OMC Cobra 4.3 V6 no longer engages forward or reverse

Jerry,

Well, first of all, good check on the "drive-shaft" (I do hope that if you were doing this on the trailer you used some sort of flush adapter)

It's very possible that the drive is NOT shifting into gear in either direction but if it was only going partially into gear, you would hear some "grinding/clicking" or something.

Since it doesn't do the same thing in FWD and REV, I would start at the lower shift cable and see if it is moving the correct amount in either direction.

To change a lower shift cable, you'll have to remove the drive. I would do that anyway since I would want to set the drive up on a stand and shift it manually using the shift shaft to determine if it actually IS shifting. If it is shifting properly, then you may have a problem with the shift mechanism in the transom mount and/or cable etc.

If you have had any problems going into gear in the past, (and you didn't get it fixed) you might have finally damaged the shift dogs enough to prevent it from going into either gear.


If you're not familiar with removing the drive, you might find someone that is..........also If you want to do any other maintenance yourself you should get an OEM OMC service manual that matches your year/Model etc.

Re: 1986 OMC Cobra 4.3 V6 no longer engages forward or reverse

HT32BSX115 said:

Jerry,

Well, first of all, good check on the "drive-shaft" (I do hope that if you were doing this on the trailer you used some sort of flush adapter)

It's very possible that the drive is NOT shifting into gear in either direction but if it was only going partially into gear, you would hear some "grinding/clicking" or something.

Since it doesn't do the same thing in FWD and REV, I would start at the lower shift cable and see if it is moving the correct amount in either direction.

To change a lower shift cable, you'll have to remove the drive. I would do that anyway since I would want to set the drive up on a stand and shift it manually using the shift shaft to determine if it actually IS shifting. If it is shifting properly, then you may have a problem with the shift mechanism in the transom mount and/or cable etc.

If you have had any problems going into gear in the past, (and you didn't get it fixed) you might have finally damaged the shift dogs enough to prevent it from going into either gear.


If you're not familiar with removing the drive, you might find someone that is..........also If you want to do any other maintenance yourself you should get an OEM OMC service manual that matches your year/Model etc.

Click to expand...

First off, sorry for using the wrong name before Rick, my bad!

I did use the ear muffs with water running and engine ran at normal temp

One thing happened when I did the test in gear with the prop the first time - after trying what you suggested with engine off, and it didn't do same thing in fwd and rev, I started it again (water running of course) and tried fwd and reverse. ONE time the prop spun in reverse with some clicking noise, then it wouldn't do it again. Would not spin in fwd. No other noises when in gear.

So, maybe a lower cable, is that bad?

Thanks again.

Re: 1986 OMC Cobra 4.3 V6 no longer engages forward or reverse

I changed my lower shift cable last year on my 90' OMC Cobra with a 4.3 litre. Wasn't fun snaking it down the tube but a little patience and perseverance got it in. The cable adjustment at the engine needs a study of the OMC manual. Also, you'll need an OMC tool ( I went to a marina, traced it on cardboard and my tool maker father make one out of aluminum) for where the cable connects to the drive. In summary, get the real deal OMC manual. Glad that job is out of the way. She shifts like butta now.

HT32BSX115 said:

Jerry,

Well, first of all, good check on the "drive-shaft" (I do hope that if you were doing this on the trailer you used some sort of flush adapter)

It's very possible that the drive is NOT shifting into gear in either direction but if it was only going partially into gear, you would hear some "grinding/clicking" or something.

Since it doesn't do the same thing in FWD and REV, I would start at the lower shift cable and see if it is moving the correct amount in either direction.

To change a lower shift cable, you'll have to remove the drive. I would do that anyway since I would want to set the drive up on a stand and shift it manually using the shift shaft to determine if it actually IS shifting. If it is shifting properly, then you may have a problem with the shift mechanism in the transom mount and/or cable etc.

If you have had any problems going into gear in the past, (and you didn't get it fixed) you might have finally damaged the shift dogs enough to prevent it from going into either gear.


If you're not familiar with removing the drive, you might find someone that is..........also If you want to do any other maintenance yourself you should get an OEM OMC service manual that matches your year/Model etc.

Click to expand...

Re: 1986 OMC Cobra 4.3 V6 no longer engages forward or reverse

When I first read your post, it sounded to me like a lower shift cable. It usually breaks at the drive- -where all the tension is from trimming- -so take a look to locate it and see. As HT3..... suggested it was good to check the shaft too but it sounds like a lower shift cable to me. FYI: there was recall on that cable and at the time OMC replaced them under warranty on the era of OMC that you have. I found my replacement on the web rather easily. Can't remember how much but it was around $50.

jerryromero said:

First off, sorry for using the wrong name before Rick, my bad!

I did use the ear muffs with water running and engine ran at normal temp

One thing happened when I did the test in gear with the prop the first time - after trying what you suggested with engine off, and it didn't do same thing in fwd and rev, I started it again (water running of course) and tried fwd and reverse. ONE time the prop spun in reverse with some clicking noise, then it wouldn't do it again. Would not spin in fwd. No other noises when in gear.

So, maybe a lower cable, is that bad?

Thanks again.

Click to expand...

Re: 1986 OMC Cobra 4.3 V6 no longer engages forward or reverse

One thing happened when I did the test in gear with the prop the first time - after trying what you suggested with engine off, and it didn't do same thing in fwd and rev, I started it again (water running of course) and tried fwd and reverse. ONE time the prop spun in reverse with some clicking noise, then it wouldn't do it again. Would not spin in fwd. No other noises when in gear.

So, maybe a lower cable, is that bad?

Click to expand...

Yeah. That would make me look closely at the lower shift cable. the drive must come off anyway so you can easily check that the drive itself is shifting correctly.

Re: 1986 OMC Cobra 4.3 V6 no longer engages forward or reverse

4Winns2 said:

When I first read your post, it sounded to me like a lower shift cable. It usually breaks at the drive- -where all the tension is from trimming- -so take a look to locate it and see. As HT3..... suggested it was good to check the shaft too but it sounds like a lower shift cable to me. FYI: there was recall on that cable and at the time OMC replaced them under warranty on the era of OMC that you have. I found my replacement on the web rather easily. Can't remember how much but it was around $50.

Click to expand...

Thanks so much for all your help. I will check into the lower shift cable. This is something I'm not sure that I will have time to do myself but I can check to see if it broken. I sure appreciate the helpfulness of this forum and hope that sometime I can return the favor!

Cheers! Jerry

Re: 1986 OMC Cobra 4.3 V6 no longer engages forward or reverse

HT32BSX115 said:

Yeah. That would make me look closely at the lower shift cable. the drive must come off anyway so you can easily check that the drive itself is shifting correctly.

Click to expand...

Thanks so much for your help Rick, I really appreciate your willingness to help!

Jerry