Evinrude Power Trim

See this picture:

is it about this problem?

 

Yes, but the tilt lowers all the way down when I accelerate and the boat does not advance it only revs!

 

sounds like 2 problems
If the engine tilts up to where you can pull the trail lock down then it has enough oil to hold the trim
The oil is checked when its full up
A failed seal on the end of the manual tilt release screw can make it leak down under load. Its secured in its location with a internal circlip.
( plus there are other valves that can cause the same fault)

You need to be sure your prop hub is not slipping as mentioned above

 

I'm gonna look into all that tomorrow. Thanks and happy new year!

 

We'll, I removed the prop and everything at that end looks pretty good! The prop hub doesn't need to be replaced, so the issue must be something else! Maybe I had the outboard tilted out too much, I'm not sure, any suggestions anyone?

 

The electric trim/tilt pumps hydraulic fuel from one side of a piston to the other one. Tiny check valves keep the fluid there so it cannot flow back through the pump and there also is a valve in the piston that allows fluid to quickly move if the drive hits something.

Wear or a small particle can prevent a valve to fully close, so the force acting on the drive may change the trim position. If that happens and the drive stays pulled in when you throttle back, the hydraulic unit must be overhauled.
If the drive reverts to its proper position, there is just some air trapped inside.

 

I have a hydraulic circuit diagram for this, when I get home in 2 weeks I will post it
Off the top of my head I cant remember which valve is which it has been 25 years since I was passing exams on that system
There are no valves in the trim pistons so its one of the valves under the the large straight looking screw heads ( the screw head is part of the valve)
You need a giant screwdriver to remove them ( or the correct tool)

 

Ok thanks powerabout, I'll bee waiting for that diagram. I took it out again this weekend for peace of mind and it turns out that I was tilting out excessively like in the picture above, the first example on there. I also want to thank you Nakupanda for posting those examples! I had seen and read about that before, but I guess I was a little over excited and overlooked the issue. Everything seamed to work pretty good yesterday that we took it out so, thanks again guys!