[folkj]

Mariner 40 Hp Magnum Oil Injected.
Possibley a 4cyl
Unsure of Year (here are the possible serial numbers, I was told its 1990):
1-8871-C
016905
OC 287943

I recently just starting having an issue with the power trim not able to trim up. When motor is not in gear I can trim the motor up and down all the way with no problems, but when in gear it seems there is not enough power to trim it up.
I checked the oil level on the cylinder and red oil came out as soon as I opened the screw. I don't believe there are any problems with the oil level.

Hoping its an easy fix!

[BoobieBouncer]

Check the oil level with the motor trimmed all the way up.

If it is low then it could have sucked air into the lines.

You may need to bleed the air out of the system.

[folkj]

I checked the oil with trim all the way up, the level seems perfect. Never had any problems in the past until now. No leaks either.

How do I go about bleeding the air out?

[westexasrepublic]

having the same issue....waiting for answers. But I read somewhere the system is "self bleeding"?

[BoobieBouncer]

The reservoir is self bleeding, but the hydraulic cylinders are not.

There are screws on the top and bottom side of the cylinders for bleeding.

Follow your repair manual steps for your model.

[folkj]

I found the release value on the reservoir at the base of the pump. Can't believe I didnt see it before. Just have to unscrew with flat head screw driver.
Anyway, I lifted the trim all the way up, opened up the release valuve to let the motor down, (thinking this would help bleed the air our, did this 3 or 4 times) but no such luck.
Trim still goes up and down but when I apply pressure while trying to lift the trim its still to weak to lift.

I don't have a manual yet. I have one on order with the local marine shop but won't be here for another 2 weeks.

With out taking the entire power trim off I can't locate any relief valves top or bottom of the cylinder, only reserve pump.
I'm starting to think the problem is with the seals, perhaps air is leaking out and not able to build enough pressure. Again I have no oil leaks anywhere.

Any help would be appreciated.

[folkj]

Not sure if this helps, but here is a complete diagram of the power trim.

www.crowleymarine.com/mercury_parts/543/300.cfm