1993 OMC Trim unit

[xsmarine]

I have a 1993 OMC Cobra when I took it out of winter storage I noticed that the drive unit kept dropping. At first I blamed the kid for screwing with the trim switch LOL. then I noticed it would just lower over time. There is no visible leak in the engine compartment. can someone give advice or direct me to related links.

Thanks in advance,
Craig

 

[Barnacle_Bill]

Is the manual release valve loose?

 

[jerryjerry05]

If it drifts down: Usually the hyd. pump an o-ring or check valve has gone bad.
They don't sell them anymore.
Maybe a hyd. pump repair shop or buy a used from e-bay or a salvage yard.

 

[xsmarine]

Thanks,

I will have a look at it tonight. Hopefully it is just a bad o-ring and I can just find a suitable match.

I am new to outboards and now starting to think the OMC Cobra might have been the wrong choice. Are there any factory parts left or is it just used and OEM stuff?

 

[Boat Doctor1]

Every mfg has same problem- service dealers should have the proper test gagues to check it. I do here- the trim / tilt unit must be removed - & if my old memory is good?? haha??- there are at least 2 large screwdricer type valves that must be removed & o-rings replaced on those! Should be possibly? some in the pump area itself .??

 

[xsmarine]

I came home on the weekend to take a look at the trim pump. The skeg had actually sunk into the pavement in the driveway. I raised the outdrive up and went in the house for the night. I came out in the morning to start looking at the issue and the out drive was still in the same position and hadn't drift down at all. It has been several days now and everything seems to be okay. Is it possible one of the seals had dried out over the winter and is now lubricated and working? Should I still take a look at it or leave well enough alone?

 

[JJBoatr]

Xsmarine,
I am fighting the same issue on my 92 Cobra. I just rebuilt the trim cylinders because the starboard cylinder had a small leak. The drive however is still lowering on its own, but it is slower than it was before. Like yours, my drive will stay put in the full up position but if I leave it at about the halfway point the cylinders will retract about 2" over a period of 24 hours. Might be worth a try to check yours in this manner to be sure. Because when you're underway the force exerted on those cylinders by the prop pushing the boat will most certainly push them in faster. There is a seal kit available let for the pump manifold from BRP. It is priced around $50. I am currently trying to find some good instructions on how to rebuild mine. Hope you got lucky and just had a dry seal that started to work again.

 

[JJBoatr]

The link to the seal kit for the pump valve body is below. This kit is for my model number 502APRAMK which is a Ford 5.0/HO with Cobra drive. I don't see why trim pumps would be any different, but just to be safe make sure to input your own model number when searching for your parts.

http://www.crowleymarine.com/parts/2051.cfm

 

[JJBoatr]

My problem ended up being a bad trim cylinder. I found it to be internally faulty buy putting the drive about halfway up, disconnected the down lines (AFT Lines). Expect a little bit of fluid to escape while you are disconnecting them. Once that initial loss of fluid is cleaned up, just monitor the open cylinder ports. Whichever one continues to drip is the bad cylinder. If both drip equally, the problem may be in your pump manifold. Good luck. There is a better description of this process on here somewhere I will try to locate it for you.

 

[pantaloonz]

I'm having the same issue.. I notice that if I leave the trim 1/2 way ... in the morning it's completely down. I guess I will try and put the trim all the way up and see if it holds there.

-Pantz

 

[JJBoatr]

FYSA...I have run my boat twice with this condition and despite what I thought, the prop thrust is not pushing the lower unit full down quickly while up on plain. I am definitely going to replace the cylinder but for now I'm just running it.

 

[xsmarine]

I will be heading up this weekend to do some boating /fishing. I will test to see if it stay when only partially extended. I was hoping it was just a dry o ring because it functioned fine at the end of last season. But I am always to optimistic.

 

[JJBoatr]

Nothing wrong with optimism so long as it doesn't turn into denial

 

[pantaloonz]

did either of you come to a conclusion on your issue or are you on hold for now?

I've taken my boat out twice now, the trim is behving normally from what I can "feel" It's running pretty damn well too, it pulled me water skiing quite nicely!

The interesting part for me is that the stays when all the way up. If there was a bad cylinder.. wouldn't it just go down over time..every time?

-Pantz

 

[JJBoatr]

pantaloonz,

If you read above you will see that I diagnosed my problem to being a bad cylinder. I wouldn't discount a cylinder as the culprit just because the leg will stay in full up because the cylinder will wear more in the mid range. That is my guess anyway because that is where the unit is positioned and moved around the most. I would recommend you test your cylinders as I did in the following manner:

1) Raise your Lower Unit to the mid way point of travel
2) Remove the plastic cover on your cylinders to expose the trim lines.
3) Slowly disconnect the "down" lines...Aft on the cylinder.
4) After the initial fluid loss from disconnecting them (won't take long), clean the area to remove residual fluid.
5) Now sit and wait for one of them to start leaking.

Which ever cylinder continues to drip fluid is your culprit. This indication tells you that fluid is internally transferring from the high pressure side to the low pressure side of the cylinder. Good luck.