OMC 4.3 Lower unit loses trim

[geoooo]

Hi,

I have a 1989 OMC 4.3 that I just bought. After I lift the boat, the unit slowly drops to vertical within a few hours. It seems to work quite well under normal operation, although it does seem to require a tweak up now on then.

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.

Could it be that the cylinders have seals that are leaking back into the reservoir?

TIA,

-geoooo

 

[Bondo]

Re: OMC 4.3 Lower unit loses trim

Ayuh,... The Pump has a check valve in it that can be leaking,+ the rams might have a valve that can be leaking....
Though it's More likely the pump...

 

[geoooo]

Re: OMC 4.3 Lower unit loses trim

Thanks for the quick reply. Ok, wishful thinking. I think rebuild kits are available for this pump. Do you think it's worth considering? Or should I get an aftermarket pump? I will not be doing this myself.

TIA,

-geoooo

 

[MToma1]

Re: OMC 4.3 Lower unit loses trim

Mine did that for two years. I got a rebuild kit and replaced all the O-rings. Works like a charm and never falls down even after months. Its easy to do, but you will have to bleed off the rams after your done. All of its in the manual. You can make a bit of a mess but easy.

 

[geoooo]

Re: OMC 4.3 Lower unit loses trim

Thank you and Bond-O for your replies - very helpful.

 

[geoooo]

Re: OMC 4.3 Lower unit loses trim

One more question. Whether this be a ram or pump issue, as long as fluid is not leaking to the outside, is there any danger in waiting until the end of the season to fix this? For now, it's only a minor inconvenience, but OTOH I don't want to inflict any damage.

TIA,

-geoooo

 

[Bondo]

Re: OMC 4.3 Lower unit loses trim

Ayuh,... The only Damage I could see would be the drive dropping, while in shallow water....
It won't hurt the hyd. system any... Just the Prop, if you run aground...

 

[geoooo]

Re: OMC 4.3 Lower unit loses trim

No problem there. It's a very gradual process, even at 40 mph.

I don't know how/when threads get closed, but I've gotten all the help I need on this one. Thank you.

 

[Bondo]

Re: OMC 4.3 Lower unit loses trim

I don't know how/when threads get closed, but I've gotten all the help I need on this one. Thank you.

Ayuh,... Usually threads are only closed if there's a Problem, such as posting to somebody else's OLD thread...
Otherwise they just drift into the archives for learning purposes to other posters...

 

[geoooo]

Re: OMC 4.3 Lower unit loses trim

I totally resemble that remark :redface: Thanks again.

 

[geoooo]

Re: OMC 4.3 Lower unit loses trim

I guess it's not over yet. I'm trying to locate a trim pump (surprise), and I'm finding numbers like 986278, 985846, 912018, 986960, 3850033 (Volvo x-ref I think).

If it's my "trim pump" that's the cause, what # should I be looking at? And is there such a thing as a rebuild kit for the pump? I can't seem to find it now.

Better yet, anyone have a link to the proper trim pump that I can just buy? My OMC # is 432APRMED.

 

[geoooo]

Re: OMC 4.3 Lower unit loses trim

Thank YOU,

I bought a used pump / motor / manifold which I will deliver to my mechanic along with new RAM seal kits. He is a Penta-authorized service dealer and "says" he knows his stuff.

I hope he's able to diagnose Rams vs Pump (is this possible?) with some sort of pressure leak-down tests or whatever, and if he can't rule out either beforehand, then to replace one, check if the trim still drifts downward, and if it does, replace the other.

I'll let you know and post my results as soon as I find out. Thanks for your time.

-George

 

[geoooo]

Re: OMC 4.3 Lower unit loses trim

Just for closure, I can report that it was something in the trim-pump assy, guessing the check-valve. I bought a used pump/motor assembly on-line for $250, and now it's steady as a rock. Thank you guys.