Merc 40 HP power trim won't lift, even manually

[tamadoug]

I have a 95 mercury 40HP (serial#0G291100 - black plug on the trim motor). It sat for two years. The power trim will not lift now, even manually. The motor runs freely when running down and grunts with no movement when the "up" switch is pushed. (It didn't move down cause it was already down.) I opened the manual release valve per the manual and I still couldn't lift it by hand. When we opened the fill plug, fluid came out and then we could move it (manual valve was still open 3 full turns). As we lifted the motor, it push the fluid out of the drain as if the fluid was on the wrong side of the piston (picturing a basic hydraulic cylinder in my head). Anyhow, I need to order parts and get it fixed ASAP. I am hoping that someone can point me to the most likely root cause so I can get the right parts on order. I will probably break it down in the AM before work and see what I find, but I really don't know what I am looking for. Based on other posts, I will look at the control valves. I appreciate whatever guidance I can get. Thanks in advance.

 

[RRitt]

Re: Merc 40 HP power trim won't lift, even manually

hmm ....
my first guess would be that the manual bypass seized into place and the tip snapped off. get a bucket. go ahead and fully remove the manual bypass. There needs to three orings. If not then the tip is somewhere inside your system and the system will not run again until you find all parts and debris and remove. If you do have three orings then your rocker arm probably has some surface rust and needs to be worked free (without damaging). The rocker arm actuator has to slide perfectly for that pump to work. Even the smallest bit of surface rust or debris in the actuator can cause complete failure.

 

[tamadoug]

Re: Merc 40 HP power trim won't lift, even manually

Thanks. I will take it apart and check it out tonight. I appreciate it.

 

[RRitt]

Re: Merc 40 HP power trim won't lift, even manually

be cautious and slow if you take it too far apart. Hydraulic pumps can be humpty dumpty things. They don't go back together very well.

 

[tamadoug]

Re: Merc 40 HP power trim won't lift, even manually

So I took the manual bypass out and as you suspected, two o-rings. I didn't get any deeper into dissassembly last night than taking the two SHCS from the cylinder side and removing the pump base from the motor. Do you think that it is safe to order the manual bypass and an o-ring kit and that will cover all that I need to get going? Thanks again for your help.

 

[tamadoug]

Re: Merc 40 HP power trim won't lift, even manually

OK, have the unit off and the thing split. How do I get the piece of the valve body out? Can you punch it out from the opposite side? drill, needle nose?

 

[aussieflash]

Re: Merc 40 HP power trim won't lift, even manually

Has it snapped off or are you just missing the O ring.Is the end of valve pointed?I have seen valves with only 2 orings.

 

[tamadoug]

Re: Merc 40 HP power trim won't lift, even manually

Thanks for the reply. It has three o-rings. The third o-ring and the tip were broken off. You can push it from the opposite side with a really, really small punch. I am good to go...I hope. I will put it on the boat tonight and see if it works. Thanks all.

 

[RRitt]

Re: Merc 40 HP power trim won't lift, even manually

OK, have the unit off and the thing split. How do I get the piece of the valve body out? Can you punch it out from the opposite side? drill, needle nose?

It's not easy. I do enough of them that I made my own tools. a square and true jig for the drill press that drills a 1/16" hole to the perfect depth without damaging the aluminum plus a super-long and skinny screw extractor. I don't remember what I tried before I made the tools. I do remember that I was killing about 30% of the pumps and that is why I built the tools.

another lesson learned is to polish the rocker arm actuators so that they have a silky smooth movement. a metal lathe (or good drill) and some 1200 wet dry works well. Rocker arm pumps are on the verge of breaking even when new. even the smallest burr or debris can cause failure. carefully examine the actuator piston for even the slightest damage.