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Johnson wont tilt

lineman

New member
" I have a 79 100HP Johnson th

" I have a 79 100HP Johnson that wont tilt or trim, I installed a new motor and it is running in both directions, pulled the check valve out and it looks good, pulled the shuttle valve out and it looks good, with the motor up and locked the trim pistons work in both directions, tilt piston doesnt, with the engine down the motor runs but it wont lift the engine, Im going nuts, can you help? "
 
"Lineman..... Did you refill t

"Lineman..... Did you refill the reservoir? Did you close the manual release valve? To fill, have the engine at its extreme up position, on the starboard (right) side of the PTT assy, fill the reservoir until it starts to overflow at the fill hole, then replace the screw plug.... make sure the "O" Ring is still on the back of the screw.

Does it operate now? If not, did it operate prior to replacing the electric motor?

Joe (30+ Years With OMC)"
 
manual release valve is shut

manual release valve is shut and reservoir is full I replaced O rings in release valve and check valve and it worked all last year after I replaced the trim motor
 
"Lineman.... The valve that se

"Lineman.... The valve that seperates the tilt cylinder from the trim rams is naturally called the Tilt/Trim Seperation Valve. It is located on the port side of the PTT unit and unfortunately cannot be accessed without removing the unit, or removing the port transom bracket. Frankly, I've never heard of this type situation, or of having that valve jam to a point whereas fluid could not be forced past it.

You say that when the engine is down and you atempt to raise it, the trim rams extend to their limit, then the unit goes no further. Does the sound of the electric motor at that point change, such as it had suddenly encountered a unexpected load.... or does it simply keep running at its present sound and rpm?

If, when finished with the boat the last time the PTT ran normal, you did not pull in the trim rams to trailer the rig, it's possible that the oil pressure has exceeded the 1700 psi limit of the oil pump (caused by the engine jumping up and down and the tilt cylinder acting like a oil pump when trailering). This problem causes the oil pump to be ineffective.... but that should also cause the trim rams to be inoperatable. However, see the following just in case a weird problem has popped up here.

(PTT Hydraulic Lockup)
If the engine has been trailered without having both of the trim rams pulled in, or trailered without even having the engine being supported by the trailering support, it is possible for the PTT to encounter a hydraulic lock up. The slight up and down motion, when trailering allows over 1700 psi of oil pressure to build up on the wrong side of the oil pump. Since the oil pump cannot exceed that 1700 psi, the unit is effectively hydraulically locked into position (the elec motor runs and does nothing).

The proper method for trailering is to have the engine in a full tilt position and resting on the trailering support bracket, then have both trim rams pulled in to a point where the engine makes a jerking motion. At this point, immediately take your finger off of the PTT trim switch. Now, quickly and sharply, tap the PTT up button. This removes the vast majority of down hydraulic pressure but at the same time, the engine is solidly locked into position and cannot rock up and down.

(The Cure)
Have the engine in the up position and supported so that it cannot fall. Look straight at the PTT assy.... you will see what looks like a large slotted screw, but which is in fact a check valve. Remove that valve and what you find inside which is a shuttle valve, and a spring on each end of that shuttle valve.

After you've removed those items, look straight inside of that chamber. You'll be looking at the reverse side of another check valve. Look at the hole in the backside of the valve you removed. You will need a punch that will fit inside of that hole.

Now, place the punch inside of the hole in that check valve that is still in the unit, and tap it rather sharply with a hammer. It will take quite a rap but the idea is to unseat the valve to release the hydraulic pressure. Watch your eyes as when you do release the pressure, it will have a tendency to spray out somewhat.

After releasing the pressure, reassemble the shuttle valve, springs, and outer check valve. Fill the oil reservoir with PTT fluid, having the engine in the extreme full tilt position. That's it.

Joe
"
 
" I already checked the inside

" I already checked the inside check valve that you spoke of and it is not locked up as it will move and fluid will come out. I don't trailer the boat, it is kept in the water in the backyard. The sound of the electric motor doesn't change when the trim pistons are all the way out. The only time I can get the trim pistons to move is when the engine is up. If the engine is down, the electric motor turns but the trim pistons will not lift the weight of the engine. I'm stumped. "
 
" I think I got something now,

" I think I got something now,I was messing around liftin and pushin went to release pressure and the screw was not seated , screwed it in tighter and then it worked but now its leakin fluid, I think I got the wrong O ring for the release valve would you happen to know what size or diameter O ring? either way I think I can handle it. I got the new size prop you told me about some months ago cant wait to try it out , thanks "
 
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