POWER TILT TRIM Electric Motor Differences – by Joe Reeves
The 3 wire unit incorporates a solenoid for the up mode, and direct wiring for the down mode. The 3 wire motor has a “Black”, “Blue”, and a “Green wire. Battery negative (-) connects to the black wire… Battery positive (+) connects to either the “Blue” or the “Green” wire to have the motor run in one direction or the other.
The 2 wire (One “Green” wire, One “Blue” wire) unit incorporates a complex relay setup for both the up and down mode. Via the relay system, the battery negative (-) connects to one of the motor wires, the battery positive (+) connects to the other motor’s remaining wire causing the motor to run in one direction. The wires being reversed via the relay system causes the motor to run in the opposite direction.
The two different type electric motors cannot be interchanged “UNLESS” their associated wiring system (relay/solenoid setup) is interchanged with them.
POWER TILT TRIM Electric Motors 1976 – 1992
Three (3 ) Wire POWER TILT TRIM Electric Motor:
This PTT electric motor existed between 1976 thru 1981.
The original OMC part number is 387277 and supersedes up thru the numbers of 582048, 582155, and finally to its present part number of 584107. It appears to be unavailable at Bombardier but it might be available at Sierra under Sierra’s part number of 18-6761.
Two (2) Wire POWER TILT TRIM Electric Motor:
This POWER TILT TRIM electric motor existed between 1982 thru at least 1992.
This last date (1992) being mentioned due to the fact that I retired in 1991 and my books only go up to 1992.
The original part number is 391264 and supersedes up thru the numbers of 393988, 394176, 434795, with its last number being listed as 985237. This electric motor appears to still be available. It may also be found at Sierra under Sierra’s part number of 18-6759.
Yes, either electric motor is expensive but prices are not listed here as they seem to change about every six months or so.
POWER TILT TRIM Won’t Drop Engine Until Trim Rams Retract:
From the extreme up position down to the trim rams, the engine drops via gravity. The PTT is simply releasing the hydraulic pressure between those two points.
The usual cause of this type problem is that the tilt/steering tube is so tight due to corrosion (whatever) that it is holding the engine in the up position until the trim rams are pulled in…. then hydraulic pressure takes effect.
The cure is to loosen one of the large tilt/steering nuts 1/2 turn, then with a 2×4 and a large hammer force the swivel bracket sideways slightly. Force grease into the grease fittings on the front of the swivel bracket. That should do it.
POWER TILT TRIM Temporary “Down” Lockup
A problem that takes place in various POWER TILT TRIM units is that a boater will trim the engine all the way up, then attempt to trim it down, only to hear the PTT electric motor running and nothing happening… the motor is not moving downward. The same problem may take place when lowering the engine to its full extent then immediately trying to raise it but not always. Then, after waiting a short time, the boater finds that the PTT unit is functioning properly once again.
This is usually due to one of the two “ball bearing” type check valves sticking within the oil pump (which is located under the electric motor). At least this is what I’ve found to be the case in every instance I’ve encountered this problem…. and it is usually the “ball” check valve pertaining to the “up” mode.
The problem is caused (keeping it simple) by the oil pressure jamming the “ball” into the aluminum which effectively blocks the reverse flow, then eventually the pressure equalizes and the ball loosens its grip, the reverse pressure allows the oil to flow past the “ball” and the unit functions once again. Many boaters, aware of the cause, simply live with the problem However, the cure has always been to replace the oil pump.
POWER TILT TRIM 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 assembly…. you will see what looks like a large slotted screw on the port (left) side of the PTT assembly, 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.
POWER TILT TRIM Oil Pump Air Lock
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 recommended) 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!).
Editor’s note: Please be sure to check your engine parts diagrams or our application guides to confirm the correct parts for your motor.
