1986 Mariner 150 Magnum power trim problem

[Mats]

Hi everyone,
I have a weird power trim problem that I haven't found described in any forum so far. When trimming down the engine it won't stay in the down position. It seems to be some over pressure in the system.
It all started when I asked a good friend of mine running a outboard repair shop to fix my leaky power trim. He did fix the leaky part, but can't get the engine to trim down and stay in the down position. He has been trying to fix this issue for over a year and now told me he's giving up. Apparently he has consulted fellow mechanics, but no one has been able to tell what mighty be wrong.
Anyone have a rough idea what might be the problem?
Cheers,
Mats

 

[QBhoy]

Some options might be that the vent screw is leaking or not sealing or there is water in the hyd fluid.
When you say it won’t stay down, you mean it will tilt up when in reverse ? Defo check the vent screw is not passing.
It could also be that the internal valves are passing in the pump and not holding pressure.

 

[Mats]

The engine won't stay in the down position at all. Boat is on a trailer so the reverse gear has no effect. There seem to be an over pressure in the system that pushes the engine slightly up from the down position. I don't think this can be related to a leak somewhere.

 

[Watermann]

Is your motor an inline 6 or V motor and does it have the single center ram or is it a double rams with a remote pump?

 

[Mats]

It's a v6 with a single center ram with an integral power trim pump.

 

[Watermann]

Can you take a video of the event your talking about and post a link to it here? Really don't think I've heard anyone describe having your specific problem before. There should be someone around that has though and the video just might be help.

 

[Mats]

The engine is hanging in my garage now. I will see if I can hook it up to a battery and make a video on the weekend.

 

[Dukedog]

It's a v6 with a single center ram with an integral power trim pump.

should be two trim and one tilt cylinder, pump all on clamp.... single tilt n trim ram on clamp, pump in boat... went away on production motors in '83....

hope ya'll figure this one out.. have never heard of this before...........???

 

[merc850]

Since this is a hydraulic issue and could be a common occurrence in some other equipment maybe searching for "hydraulic pump problem" might be helpful,

 

[QBhoy]

What about the chance of water, as mentioned earlier ?

 

[jimmbo]

Has the air been bleed from the system and the fluid at the correct level?

 

[Mats]

A bit surprised to find the whole power trim assembly missing on the engine when I went out to do the video in the garage. It was still lying around in the repair shop. I have now assembled it and when testing it there was air in the tilt was not running smoothly and the power trim motor was working really hard when pushing in the trim rods. Filled up with hydraulic fluid and ran the tilt up and down and refilled more fluid several times. With refilled fluid the tilt runs perfect, but the trim rods won't move at all. They are stuck in the most trimmed out position. When the rig is tilted down to the the trim rods, it sounds like they hit solid metal.
I'm a bit hesitant of what to do now, as the mechanic told me that when the motor didn't stay in the trimmed down position, he had loosened the release pressure valve and it went flying some 30 feet and sprayed the whole wall of his shop full with hydraulic fluid. I wouldn't want that to happen in my garage. We currently have 15 inches of snow and it's freezing outside (Sweden) so no option to take the engine outside at the moment.
Am I right in the assumption that I need to loosen the pressure release valve to get the trim rods to move in?

 

[jimmbo]

What I remember about my 84 115(which used the same Tilt/Trim system), loosening the manual release screw allowed me to tilft/lift the motor up out of the water, regardless of where it was sitting. Letting the engine down was a different matter, the engine would drop, and the trim rams, if they were less than all the way out, would extend to their fully out position and that was as low as the engine would drop. Any lower/inward required the trim pump to be working.