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Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4716
Experience:  42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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2004 mercury 75 hp 4 stroke will not go all the way up on

Customer Question

2004 mercury 75 hp 4 stroke will not go all the way up on the power trim. It will go about half way up , but no further . I tried bleeding the system repeatedly but with no improvement. The power trim worked ok before the winter storage. Hope y ou can help Bill
JA: Sometimes things that you think will be really complicated end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Is there anything else important you think the Marine Mechanic should know?
Customer: The ram retracts about 3/8" after the power up. The pump motor is not cutting out and the sound of the moter /pump does not change too much when it ceases to elevate the piston.there is fluid in the resevour when it stops
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Marine Mechanic about your situation and then connect you two.
Submitted: 6 months ago.
Category: Boat
Expert:  Jeff G. replied 6 months ago.

Was the trim fluid level low when you first checked it?

Release the manual release valve, Turn it out a couple turns. Pull up on the engine all the way. Turn the release valve in, put the trailer leg down. Let it sit for a couple minutes, now check the fluid level. If the fluid level is OK then trim the unit all the way down. Trim up and see how far you get, pull up on the lower unit at the same time, does it go up further?

Is the titl tube where it swivels in the front of the engine greased and free?

Customer: replied 6 months ago.
fluid was not low when I checked. tube and swivel points are lubricated and free. After manually raising ,leaving up and then lowering down the results were the same as before. I tried lifting manually with the pump powered but as soon as I let go the piston retracted to the mid way position. when I checked the fluid level there was air pressure and bubbles in the oil
Expert:  Jeff G. replied 6 months ago.

The trim fluid has to be added when the unit is fully tilted. From your description it is a little low on fluid. The trim has two circuits the trim circuit and the tilt circuit. Your trim circuit seems to be working but the tilt is leaking down. Stuck check valve, leaking manual relief, or low on fluid.

How is the fluid level when fully tilted?

Customer: replied 6 months ago.
fluid level full at full tilt when raised with tractor bucket
Customer: replied 6 months ago.
it is not clear as to whether my messages are sent or not
Expert:  Jeff G. replied 6 months ago.

Are there any messages you sent that are not on the screen?

Is the trim portion working but not the tilt range?

Can you get me the serial number of the engine?

Customer: replied 6 months ago.
messages are ok..tilt up only goes about midway then stops with hydraulic motor still running . trim or down operates within that midway up range.mod 75 elpt 4s ser. ot942762.I was looking a diagram of this system and it showed 2 up relief valves
Expert:  Jeff G. replied 6 months ago.

Air in system, defective component.

Remove the E ring then the manual relief valve. Allow the trim fluid to drain into a clean container. When drained check the fluid, is there shavings, black specs, debris in the fluid?

Check the O rings on the valve, all of them must be in perfect condition, if rough or cut it will allow fluid to bypass. Are all the O rings intact and there? I've seen them break and stay in the unit.

Check these and let me know what you find.

Customer: replied 6 months ago.
turned out nylon shoulder screw and caught fluid in a mason jar . I did not see any debris or water in the fluid,The screw has 3 orings. The center one seems to be flush with the surface of the screw The others show a more typical profile , slightly above the top of the groove
Expert:  Jeff G. replied 6 months ago.

Refill and flush and replace those O rings. Do you have any experience with hydraulics, or intricate repairs if we need to go further?

Customer: replied 6 months ago.
I ordered an oring and seal kit for this unit and I will start with the 3 orings on the valve screw . I do not consider my self to be a hydraulics guru though I know the basics.clean work area, take time to lay out components in order and also to get fishing buddy over to my shop. He has considerable experience and likes fishing on my boat so to answer your question yeah we can go further
Expert:  Jeff G. replied 6 months ago.

If you need I can get you the repair manual for the trim.

Customer: replied 6 months ago.
I finally got the o ring kit and installed the orings on the nylon screw but it still is not going up all the way
Expert:  Jeff G. replied 5 months ago.

More than likely one of the check valves is open, probably from hitting something in the past. I'm going to attach the chapter on the trim. This should get you where you need to be.

Download the file from here;

https://www.dropbox.com/s/5v0faulnp5us2l8/5b.pdf?dl=0

Customer: replied 5 months ago.
I removed the entire tilt trim .I noticed that the cylinder /piston ram did not go up and down smoothly while I pushed and pulled it by hand in fact it seized up about the same area that it stopped while installed.I then tried to disassemble the ram which involved building two different spanners. I found that the cylinder had a longitudinal crack in the bore running along the port that is built in to the outer part of the cylinder. Due to the age and condition of this unit I deceided to replace the entire assembly.Thanks for your assistance . Bill Doane
Expert:  Jeff G. replied 5 months ago.

Certainly not a common problem, probably from hitting something. Lots of Luck, let me know if I can help further.

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