1989 OMC COBRA 'Hiccup' under power

[Nates78ski]

Hey guys, I've got a 1989 Bayliner with an OMC cobra on it. While under power, at about 25 mph there's this 'hiccup' or maybe more appropriately named 'thud' every 9 seconds. When I lower it to about 20 mph it will do it about every 13 seconds. @ 30 it's about 6 seconds and @ 35-40 its about every 4 seconds.

I'm about certain it's in the lower unit. But even while running it under power, when it 'Thuds' (almost like you're hitting a small log in the water) it doesn't hesitate, lose speed, etc.

Any idea what I'm looking at before I start opening the thing up? Is it even worth it to open it up?

Best Regards,

 

[Speak]

Shift cable is out of adjustment or the dog clutch is worn. Dogs are more then likely done.

 

[HT32BSX115]

Hey guys, I've got a 1989 Bayliner with an OMC cobra on it. While under power, at about 25 mph there's this 'hiccup' or maybe more appropriately named 'thud' every 9 seconds. When I lower it to about 20 mph it will do it about every 13 seconds. @ 30 it's about 6 seconds and @ 35-40 its about every 4 seconds.

I'm about certain it's in the lower unit. But even while running it under power, when it 'Thuds' (almost like you're hitting a small log in the water) it doesn't hesitate, lose speed, etc.

Any idea what I'm looking at before I start opening the thing up? Is it even worth it to open it up?

Best Regards,

Howdy,

While the problem you mention is sort of generic to the OMG Kobra, it's pretty helpful to include the model number and engine size etc, of the package.

Now, having said that, I'll agree with Speak. You likely have had a lower shift cable adjustment problem for long enough to cause this. If it happens more than a few times, the (permanent) damage to the clutch dogs is pretty much irreversible and cannot be adjusted out.

The remedy is usually a complete rebuild of the drive (since you wouldn't tear one down just to replace the clutch dogs)

Since a complete rebuild is fairly costly, a lot of people consider either a used replacement drive or an SEI conversion.

Regards,


Rick

 

[Nates78ski]

Hey guys, The owner put this roofing patch over the side of the upper half of the lower unit. When I peeled it back and loosened the plug, water came pouring out... I'm not sure why he put this patch on there. But I'm feeling mostly certain that there shouldn't have been water pouring out of the (upper half of) the lower unit. Thoughts?

 

[bruceb58]

The patch was covering the "Do Not Remove Plug". If you loosened the plug, the retaining nut fell into the drive. Now you get to take the drive off to find the retainer. Either that or the previous owner removed it and was covering up his mistake with the patch.

 

[Nates78ski]

I'm certain he had it off before. But why was there water pouring out of there?

 

[bruceb58]

It's a water cavity. Not surprised there was water in there. Just so we know we are talking about the same thing, care to post a picture?

 

[HT32BSX115]

I'm certain he had it off before. But why was there water pouring out of there?

There probably would not be any water "pouring" out when the engine is not running but when the engine is running and the drive is in the water, that "chamber" is pressurized by the raw water pump.

 

[HT32BSX115]

Incidentally, If you have water "pouring" out there, it's not going to the engine and you risk an overheat of the engine and/or manifolds & risers.

 

[Nates78ski]

Ok guys, I got a new lower half from SEI, got it mounted and everything's great. Well.. not quite. It shifts into forward but doesn't shift into reverse. Obviously I just have the shift lever off one way or another, but if I knew which way, it might help me to only have to take the unit off once to get it right, instead of multiple times.

When i pulled the lower unit, I had the throttle in gear in full forward, as I do with Mercruisers (I know they're not the same, but, there you go.) Should that be in neutral next time?

Regards,

 

[HT32BSX115]

Yeah. You likely still have a "mal-adjusted" lower shift cable.

You need the correct OEM (OMC) service manual and there's a couple of tools that help too.

If I remember correctly, it doesn't matter what gear you're in when you pull the drive.

Have a look at the following too if you haven't! http://www.hastings.org/~stuart/cobra/

I hope you flushed the upper of any metal shavings etc......(upper & lower share the same oil)