1978 Johnson Tilt /Trim issue, Won't go down. Help?

[MPAdams]

Hello! Newbie Here... I just picked up a bass boat from an old bass-pro's estate. It is a 1978 Monark McFast with a Johnson 115 outboard, I have a problem with the tilt/trim system. It tilts up, not down. Tilt motor runs but no real movement down, and the tilt motor sounds strained trying to go down. Works great up. I can use the pressure release screw and it will go down but only to the Trim rods, and they do not move either powered or using release screw with downward pressure on engine. I can not get the engine to drop the trim cylinders at all. I have filled the reservoir and cycled it up/down multiple times to bleed unit. Does anybody have any ideas?

From viewed from the back the Tilt/Trim unit has motor on left, reservoir on the right the tilt cylinder in the middle and on each side of the lift cylinder is a trim cylinder(2 total) the Model number of the Trim unit on the outside of the mounting bracket is 115etL78c and the serial number is j4980804.

Any help would be appreciated.

Thanks,
MP

 

[Joe Reeves]

The trim rams do not retract in the manual down via the release valve mode. That model PTT incorporates a good size special electrical solenoid for the UP mode.

In the down mode, the voltage to the electric PTT motor is direct (switch to electric motor) unless someone has went to the trouble to install a down mode solenoid also..... have they?... and if so, does it click in when activated?

The PTT electric motor is a three wire motor... black is ground. Trace the wires from the motor back to its connector and disconnect it. Run small jumpers to the electric motor... does it run in both directions? If not, with voltage running directly to it, the electric motor will require repairing/ replacing.

 

[MPAdams]

Thank you, Joe Reeves! It looks like I will have to tear in to this thing and am trying to find a parts diagram. I have purchased 2 downloadable manuals and they didn't have them. I have gone to different parts supply stores online and my model year/number is not an option anywhere I can find. The only thing I have found is that it apparently was manufactured for sea use.

Do you know where I could find a parts break out to help me know what I am looking at in tear down? 1978 Johnson 115etL78c

Oh - and yes... it did run in both directions.

 

[just_james]

Look on shopEvinrude, it'll give you a part diagram.

 

[Joe Reeves]

Thank you, Joe Reeves! It looks like I will have to tear in to this thing and am trying to find a parts diagram. I have purchased 2 downloadable manuals and they didn't have them. I have gone to different parts supply stores online and my model year/number is not an option anywhere I can find. The only thing I have found is that it apparently was manufactured for sea use.

Do you know where I could find a parts break out to help me know what I am looking at in tear down? 1978 Johnson 115etL78c

Oh - and yes... it did run in both directions.

So.... with the electric motor being okay, running in both directions... did the motor tilt up and down?
Reservoir full when the engine is titled up? Manual release valve closed?
What is it that you're planning on tearing into?
The problem, it appears is simply that either the PTT switch is faulty in the down mode OR the down wire is broken somewhere between the switch and the electric motor.

 

[MPAdams]

So.... with the electric motor being okay, running in both directions... did the motor tilt up and down?​

The motor tilts up easy but does not tilt down. In trying to tilt down, the motor loads
Also, neither trim cylinder goes down.

Reservoir full when the engine is titled up? Manual release valve closed?​

Yes - filled to the threads. Release valve is closed - yes.

What is it that you're planning on tearing into?​

I plan to tear into the manifold and check each of the valve assemblies to ensure nothing is frozen.

The problem, it appears is simply that either the PTT switch is faulty in the down mode OR the down wire is broken somewhere between the switch and the electric motor.​

PTT SWITCH: I bypassed by applying power directly to the wires leading to the motor (3 wire system) and motor works in both directions - however hydraulic lift does not allow motor to go down.
WIRES: Motor works so no wire broken

Do you happen to know which internal valves operate which functions? (ie valve #63 is a direction shuttle but I don't know what functions the other valves support) THANKS! MP

 

[Joe Reeves]

At this point, the electric motor runs in both directions but the hydraulic system is not taking effect. Do the following.............................

(PTT Oil Pump Air Lock)
(J. Reeves)

When the PTT unit is as it should be, the electric motor runs, the manual release valve is closed, the unit is full of lubricant, and nothing works, the usual problem is an air lock under the oil pump Proceed with the following.

Engine in full tilt position. Remove reservoir fill plug screw. Insert a air nozzle up against the reservoir fill hole with rags (or something) packed around it to obtain a tight fit. Apply just a slight amount of pressurized air (10 psi resommended) to the reservoir. This will force the oil under the oil pump to remove the air lock. DO NOT go crazy with the air pressure (15 psi tops!).

 

[MPAdams]

Tried the air lock idea - thanks. It didn't work. Bummer. Took off the hydraulic unit and pulled all plugs and valves out and cleaned everything. I replaced some of the seals - found them at hardware store. IT WORKS!!! Thanks for the ideas and help!