Needing help changing the lower-unit gear lube on an '89 OMC Cobra 4.3L

[Andy80]

I've got a 4.3L OMC Cobra on a 89 Four Winns Freedom. I've been knocking out all the maintenance items on my check list and I'm now struggling to change the gear lube in the lower unit.

Throughout these forums I've read lots of conflicting ways to perform this procedure. With that said, I am going to stick with what the manual says and I'm not interested in trying methods used by other manufacturers. For those of you with experience on the OMC, I'm all ears.

Here's the problem, the specs on the lower unit states it holds 64oz of fluid, but I'm only able to get a quart in at a time. If I add any more than a quart, it comes right back out the fill hole. I've tried three times now and have wasted about 4 quarts of lube....:facepalm:

The manual says to drain all the used oil by removing the drain plug and dipstick. Once the oil has been drained, replace the dipstick and drain plug and then open up only the fill hole. The manual states that only opening up the fill hole "creates a vacuum". The problem I'm having is that there doesn't seem to be much of a "vacuum" going on and I cannot keep the 2nd quart of lube inside the fill hole.

The manual doesn't mention using a pump and I'm not sure if I'm overlooking something simple, or if I've got a bigger problem on my hands. I'm not wild about the idea of taking the boat to a mechanic, and finding a certified OMC mechanic is impossible in my area. With Memorial Day weekend right around the corner, I need to get this bad boy up and running before I run out of time! Any help with this matter is greatly appreciated.

Andy

 

[Don S]

Re: Needing help changing the lower-unit gear lube on an '89 OMC Cobra 4.3L

The manual says

You keep repeating that "The manual say", exactly which manual do you have. Is it the OEM manual or one of the aftermarket clymer or seloc manuals?

 

[a70eliminator]

Re: Needing help changing the lower-unit gear lube on an '89 OMC Cobra 4.3L

The fill hole is the center plug which is below the fill level so yea oil will spill out, you have to pump it in and be quick about putting the plug back in, final fill after a short run and top off through dipstick hole is ok if nesessary.

 

[bruceb58]

Re: Needing help changing the lower-unit gear lube on an '89 OMC Cobra 4.3L

Hopefully, this is the procedure you are using. I personally use a 1 gallon oil jug with a pump for it. I buy my oil in qts but pour that into the 1 gallon jug. I always have more than 2 qts in it so I am not injecting air bubbles when the jug gets close to empty.

 

[Andy80]

Re: Needing help changing the lower-unit gear lube on an '89 OMC Cobra 4.3L

Thank you all for your suggestions and quick replies. To answer Don's question, the manual is a Clymer which seems to be different than the manual Bruce posted. The instruction in the Clymer vs. the manual Bruce is using seems almost identical in procedure except the Clymer manual specifically states to "replace" the drain plug AND dipstick and then remove the fill plug to begin the process of refilling with oil. The Clymer manual suggests that this will create a ?vacuum? whereas I see no reference to that in Bruce's instruction. Both manuals do not suggest the use of a pump, but I'm now wondering if that goes without saying?
Bruce- is your manual an OEM and would be more accurate for this procedure? (It's frustrating to see variations in different manuals for such a crucial maintenance procedure like this.) What type of pump would you recommend? I suspect there is a pump with a threaded tip that will match the OMC's fill plug...

 

[Don S]

Re: Needing help changing the lower-unit gear lube on an '89 OMC Cobra 4.3L

Clymer manual specifically states to "replace" the drain plug AND dipstick and then remove the fill plug to begin the process of refilling with oil.

That is why it's not recommended to use those cheap aftermarket manuals, especially Clymers, for anything. They have so much wrong information it's scary.
If you leave the dipstick in, you can't fill the rest of the drive because it would be pressurized. You leave the dipstick out, fill the drive then put the dipstick in and snug it down. At that point you can remove your pump from the fill hole and the vacuum will prevent the oil from running out AS FAST because of the suction.

 

[Andy80]

Re: Needing help changing the lower-unit gear lube on an '89 OMC Cobra 4.3L

That is scary! I'll be replacing the Clymer this weekend. I'll pick up a pump and give it another try this time with the dipstick removed.

One last question, if the unit needs to be topped off after cyclying, is the procedure to top-off the same as filling? Connect the pump to the fill hole, remove the dipstick, and top-off to the appropriate level?

 

[Don S]

Re: Needing help changing the lower-unit gear lube on an '89 OMC Cobra 4.3L

Topping off is the little you may loose while putting in the fill plug. It's also a VERY Slooooooow process to fill through the dip stick, wait for a while and recheck the level.

PS: Seloc manuals aren't much better, and OMC is out of buisness, so you might want to get the full model number off your motor to verify the year of your engine and drive, then look on ebay for some OEM manuals.

 

[Andy80]

Re: Needing help changing the lower-unit gear lube on an '89 OMC Cobra 4.3L

Thanks Don, you've been a great help.

Andy

 

[dellsboater]

Re: Needing help changing the lower-unit gear lube on an '89 OMC Cobra 4.3L

Funny this should come up today, went to buy some Gear lube at local repair shop. He said make sure you fill it from the bottom hole, not middle as it will cause air lock. It seems with this issue everyone tells you the other is wrong. I even told him what the service manual says, and he said he was aware of that, but the manual is wrong and said he had a pile of lower units that where done that way junked sitting out back. I think the safe way is to check it at the dipstick when done and if you really want piece of mind, pull off the top cover and visually make sure it has covered all the gears. Just make sure to have a replacement oring, or be darn careful not to muck it up....

 

[bruceb58]

Re: Needing help changing the lower-unit gear lube on an '89 OMC Cobra 4.3L

Funny this should come up today, went to buy some Gear lube at local repair shop. He said make sure you fill it from the bottom hole, not middle as it will cause air lock. It seems with this issue everyone tells you the other is wrong. I even told him what the service manual says, and he said he was aware of that, but the manual is wrong and said he had a pile of lower units that where done that way junked sitting out back. I think the safe way is to check it at the dipstick when done and if you really want piece of mind, pull off the top cover and visually make sure it has covered all the gears. Just make sure to have a replacement oring, or be darn careful not to muck it up....

Look at this thread and do a search for many like it.

http://forums.iboats.com/showthread.php?t=479977&p=3247229#post3247229

Personally, I would do it the way the OMC service manual says to do it. I am sure that if the shop guy actually went to OMC training he wouldn't be giving this bad info.

For more piece of mind, fill the drive, check the level in 24 hours and check the level every time you take the boat out. That's waht I do with my Volvo and the OMC Cobra I had before it.

Absolutely no reason to take off the top cover. If you do, you should always replace the o-ring. That goes as well for all the drain/fill/dipstick holes. All gaskets/o-rings should be replaced when you change the lube.