OMC Cobra Outdrive Problems

e016188

Cadet
Joined
Jun 16, 2009
Messages
27
I'm new to boating. I recently purchased a 1991 Four Winns freedom 190 with a 4.3L and OMC cobra outdrive. The boat is clean and solid. I found some water in the oil when I drained the outdrive. I do have a good local mechanic who looked at the outdrive for me. The prop shaft is bent and worse the shaft moves radially 10-12 mils. I'm guessing the prop was bent and the imbalance produced roller bearing wear over time. I'm guessing lots of hours on the motor and outdrive. He indicated that he doesn't hear noise in the upper gearbox. Should I consider repair (I'm guessing a complete rebuild) of the lower unit or should I look at conversion to Merc or Volvo outdrive? How much will the conversion cost? Can I buy a transom mount that will allow the Merc or Volve to bolt to the 1991 4.3L? Where can I buy the conversion parts?
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,559
Re: OMC Cobra Outdrive Problems

If it were me, I would stick with what you have and see if the drive you have is repairable. That boat is really too old to be cost effective to switch to another brand drive.
 

danond

Lieutenant Junior Grade
Joined
Jun 11, 2007
Messages
1,118
Re: OMC Cobra Outdrive Problems

...wait. There's cost effective efforts related to boats??? :eek:


;)
 

danond

Lieutenant Junior Grade
Joined
Jun 11, 2007
Messages
1,118
Re: OMC Cobra Outdrive Problems

What are the compression numbers on the engine? What about cooling system pressure test? Oil pressure? That'll tell you how the engine's been treated and about how much life it might have left in it.

It's typically cheaper to fix what you have unless the whole thing is grenaded, which it doesn't sound like it is.

The water in the oil worries me, though. Cooling system pressure test will tell you what's going on.
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,559
Re: OMC Cobra Outdrive Problems

The water in the oil worries me, though. Cooling system pressure test will tell you what's going on.
I think he meant water in his drive oil which is not surprising considering his prop shaft problem.
 

danond

Lieutenant Junior Grade
Joined
Jun 11, 2007
Messages
1,118
Re: OMC Cobra Outdrive Problems

Whoops. He did say outdrive.

I was still excited to hear that boat repairs can have the word "cost" used to describe them in a non-negative way ;)
 

e016188

Cadet
Joined
Jun 16, 2009
Messages
27
Re: OMC Cobra Outdrive Problems

I do appreciate the humor and help. I studied my shop manual last night.

I'm disappointed with my mechanic. He won't work on OMC. I wish he would have told me before the troubleshooting.

I don't believe the shaft bend can be accurately measured with large end play in the shaft. I believe the end play in the shaft is due to roller bearing wear in the prop shaft bearing carrier/housing. My manual shows two needle bearings in the bearing carrier. Is it possible to remove the propeller and then pull the bearing carrier/housing from the lower gearcase without additional disassembly of the lower gearcase? Will I damage the shift mechanism or other parts on the propeller shaft if I try and pull the bearing carrier without disassembly of the shift mechanism and/or vertical drive shaft and pinion gear assemby?
 
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