OMC Cobra trim won't stay trimmed

[Joe Merone]

Sorry if this problem has been addressed on the list but I'm new and here's my problem: <br /><br />My 1986 OMC Cobra (4.3L) drive unit will not stay trimmed up while under power. If you trim it up after the boat gets on plane it'll stay for a little while and then slowly drop back down. <br /><br />When going very slow in the shallow water eveything seems fine. <br /><br />The reservoir seems full and there's no sign of any fluid leaking. <br /><br />What could be the problem? <br /><br />Thanks.

 

[TONY H]

Re: OMC Cobra trim won't stay trimmed

Sounds like your internal seals are leaking. With the load under power, the oil is bleeding past the seals back into your reservour. Sometimes it gets better as the season goes on.

 

[Joe Merone]

Re: OMC Cobra trim won't stay trimmed

Internal seals. Excuse my ignorance but just where are THEY located? <br /><br />Yeah, yeah I know - internally, but where exactly? And can I get at them without taking the boat out of the water?<br /><br />Joe

 

[crazyray2]

Re: OMC Cobra trim won't stay trimmed

the seals are inside your cylinders....they are not too bad I don't think

 

[geoooo]

Re: OMC Cobra trim won't stay trimmed

I've got a similar problem. I started a new thread.

 

[Bifflefan]

Re: OMC Cobra trim won't stay trimmed

Hi,

I'm brand new, so pardon me if I'm cutting in. I can't seem to find a "Post New Thread" button.

Anyway, I have a similar problem with my 1989 OMC 4.3 that I just bought. After I lift the boat, the unit slowly drops to vertical within a couple hours. It seems to work fine under normal operation, but just slowly drops, like a slow leak.

I had a mechanic tell me I need a new trim pump (solely from my description), but it goes up-down just fine with no problem.

TIA,

-geoooo

PM sent to you....

 

[Bifflefan]

Re: OMC Cobra trim won't stay trimmed

Internal seals. Excuse my ignorance but just where are THEY located? <br /><br />Yeah, yeah I know - internally, but where exactly? And can I get at them without taking the boat out of the water?<br /><br />Joe

Its easier to replace the tilt cylinders with rebuilt ones. And No, you really cant do them in the water as they are under water most of the time.
Replace them and then bleed the system and you should have it licked.