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Alpha One Trim Limit Switches

wblazer

Regular Contributor
Hi Guys,

I am confused about the adjustment and workings of my 1986 Alpha One trim limit switches. When I push my control switch to the down position the drive goes completely to the full down position. I guess this is normal.When I push the button to the up position it comes all the way up as pushing the trailer position. I looked in the Merc manual that I down loaded a while back and the adjustments were not clear to me. There are two switches port and starboard. Why two switches? And could some one help me with the troubleshooting of the switches. Thanks for any help given.
 
The 2 are TL (trim limit) and TS (trim sender).The TL works in the up position untill it`s limit is reached, then trailer button takes over. If you can raise it all the way with the trim button, the circuit has been by-passed at the pump connection.
 
How the trim/tilt works

Before you tear anything apart or replace wiring and switches, test it out; first by visual inspection by pulling back and forth on the wires while operating the switches and then test with a meter. At the commander switches, the red wire will always have 12 volts. The green wire gets 12 volts when the trim toggle is held down. The blue wire gets 12 volts only when the toggle is held up or the trailer switch is pushed in. The purple wire is part of the limit switch circuit.

If the switch voltages are as they are supposed to be then go to the trim/tilt pump assy. and make sure the purple wire connector (single wire) and the blue wire connector with two blue wires on one side of the connection are not corroded or loose. These are the trim position and limit switch wires. Pull them apart and inspect; they should be clean and tight; reconnect them. If necessary, trace the wires to the front of the engine near the slave solenoid. One wire is grounded near there and the other is connected to a terminal. If you don't get a voltage reading at the terminal junction, apply 12 VDC to see if the trim gauge moves. If it does, check for voltage back at the trim pump connections. If no voltage is there, apply 12 VDC there to check gauge movement.

Next check the three wire connector (RED, BLUE & GREEN) at the pump assy. This plug can vibrate loose and cause your problem. Pull it off and see if the pins are clean and not corroded; reconnect it.

The RED wire in the plug sends 12 volts from the pump assy. to the toggle up/down and trailer up switches. The BLUE & GREEN wires bring 12 volts from the toggle trim/tilt and trailer switches to the two solenoids on the pump assy.

The GREEN wire goes to the DOWN solenoid while the BLUE wire goes to the UP solenoid.

Did you check the switches with an ohmmeter? The trim/tilt switch is a 2-way switch and will show continuity only when it is toggled in each direction between two of the wires.

Up toggle connects the RED wire to the BLUE wire. Down toggle connects the RED wire to the GREEN wire. The TRAILER UP switch also connects the RED wire to the BLUE wire.

The OD trim limit switch will only send voltage to the trim/tilt switch in the upward toggle position if the OD limit switch is below the adjusted trim limit that keeps the OD being out of the water.

To test the limit switch circuit, lower the OD to the down position and slowly raise it with the trim toggle up until it stops. Then measure the distance between the trim cylinder attaching bolts. If the distance is approx. 22 +/- 1/4 inches, then the trim limit switch is adjusted properly and the commander trim toggle switch is working in the up/down mode.

Go to the trim/tilt pump assy. and make sure the purple wire connector (single wire) and the blue wire connector two blue wires on one side of the connection are not corroded or loose. Pull them apart; they should be clean and tight; reconnect them.
Next check the three (RED, BLUE & GREEN) wire connector at the pump assy. The RED wire in the plug sends 12 volts from the pump assy. to the toggle up/down and trailer up switches. This plug can vibrate loose and cause your problem. Pull it off and see if the pins are clean and not corroded; reconnect it.

The BLUE & GREEN wires bring 12 volts from the switches to the two solenoids on the pump assy. The GREEN wire goes to the DOWN solenoid while the BLUE wire goes to the UP solenoid.

Disconnect the trim/tilt assy. wires from the battery and then check each of the nuts and studs on the solenoids for clean and tight fittings. Each solenoid has three wires and the buss bar connected to it. The bases of them have a black ground wire and a small blue wire to one and a small green wire to the other.

On top of each solenoid, the large BLUE wire from the pump motor attaches to a large copper stud with the solenoid that has the small blue wire at the base while the large GREEN wire from the pump motor attaches to a large copper stud with the solenoid that has the small green wire at the base.

The other copper solenoid studs are connected together with a copper buss bar. One of the two studs will also have a funny looking 110 amp fuse attached to the bar. The large RED wire from the battery connects to the 110 amp fuse. This large red wire is the power for this buss bar. A small RED wire attached to the bar stud sends 12 volts to the switches which in turn sends the 12 volts to the solenoids which turns on the pump motor.

Important: if the studs on the either solenoid are dark and not like a clean penny, especially the BLUE wired solenoid, this solenoid is failing due to age and/or a loose bottom copper stud nut. The dark color comes from heat generated inside of the solenoid by the contactor because it is arcing like welding similar to points wearing out. Change the solenoid.

Cleaning Trim Limit Switch & Trim Position Sender

For the trim/tilt problem you are experiencing, if the wires from the limit switch (port side) and trim position sender (starboard side) are in good condition, they (Switch or sender) can be disassembled to clean out the old hardened grease. SCRIBE the sides of each one and the OD for a reference mark before removal. Clean out the old grease and pump fresh Mercruiser 2-4-C grease thru the zerk fittings before reinstallation. Clean the small brass contact points with solvent and a pencil eraser until shiny; repack w/ 2-4-C grease and reinstall by aligning reference marks.
 
Bt Doctur thanks for the information. Guy thanks for the in depth description of how the circuit works and how to troubleshoot it. This is much more information than I have seen in the manuals, really good stuff. I am pretty good with a multimeter and think this information will be what I need to solve this problem. Thanks again to both of you. I will post results next week end when working on the boat again.
 
Guy,

I was going to start to troubleshoot the switches as you suggested. Decided to look at the switches on the out drive before going into the boat, just to be familiar with what I would be dealing with. Both switches have the wires cut about one inch from the switch. This boat is used and not real sure of its history. I did not see any other wire except the cut ones at the switches. Is it a big deal to run new wires from the switches to the pump? Please let me know your thoughts on this.Thanks for helping.
 
I would believe more rotted away than cut.reason being the sender had 12V to all the time the key is "on".Replacements come with the wires attached and it is somewhat difficult to replace them.drive, bellows, gimbal housing need to be removed for access to the 2 bolts above the gimbal bearing.once off, remove the old wores, install the new ones, install cover plate and reassemble drive components.
 
Bt Doctur,

Thanks for the information. Don't really want to remove all those parts if I don't have to. The boat runs fine, but i was told using the trim option would increase RPM's and speed. What are your thoughts on this. Thanks for your help.
 
but i was told using the trim option would increase RPM's and speed.

Yes it will. That's why there is a limit switch. Your's is not working. You can trim by ear. SLOWLY hit the trim up switch a little bit at a time until the bow rises a little at the same time RPM's climb. If you go to far the engine will over rev--you'll know it for sure. If the boat starts to porpoise then trim down a little.
 
Guy

Thanks, that is what I will do. I have did enough work on this boat this season it is time to put in in the water and enjoy it for the remainder of the good weather.Thank you and Bt Doctur for the helpful information.
 
Guy

I forgot to ask you one question. Do I want to do this after the boat is on plane? Because it does reach plane, only I have the drive totally down.
 
Hey guys,
I realize this is an older thread but I found it doing a search for a similar problem. I bought an old boat that was missing both the trim limit and sender due to corroded wiring so I replaced both units and wiring (plus the bellows and Gimbal bearing). I was able to get the sender to register on the gauge but I am having isssues getting the "Trim Limit" switch to perform as designed.

To be specific, no matter how I adjust the limit switch I cannot find the limiting zone on the "Up" stroke of the trim. No matter how I adjust the limit switch (30 times so far) when I activate the "Up" switch for trim it will go all the way up as if I am engaging the "Trailer" switch. I have tried to find the area in which the limit puck has continuity by using a multi-meter but I don't know if the "cut-off zone" (as it pertains to the "UP" solenoid voltage) should have continuity (to stop the "UP" solenoid) or if the area of the limit switch (puck) where no continuity is what tells the "UP" solenoid to stop lifting the outdrive.


I have the instruction sheet for the pucks and I aligned the reference mark on the limit switch puck and installed it on to the gimbal ring but no matter how I rotate or adjust the limit switch puck, when engaging the "UP" position of the trim switch, it will go all the way up as if I am engaging the "Trailer" switch.


So basically, I cannot figure out how to calibrate the "Limit Switch" to work as designed. After many attempts to calibrate the position where the limit switch should stop the the "Up Trim" stroke, no matter how I adjust the reference mark and/or rotate the switch the outdrive will go up all the way to the top of the hydraulic rams extension. I know the "Stop" distance of the up stroke should be 21 3/4 inches (for the mercruiser Alpha 1 Generation one outdrive). I am mechanically inclined and have experience with wiring and circuits but my inability to get this switch to operate as it should is getting very frustrating.


If anyone has any advice or suggestions, I would be extremely grateful.
 
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First thing is to put a ohm meter across the two wires from the limit switch. Rotate it and confirm the switch actually makes and brakes.

If it does then The issue is the wiring that comes from the trim buttons has been rewired to by pass the old bad switch.



see schematic attached. It is of an older visual version but they are all wired the same.

The purple with white stripe is power from the trim switch and the trailer switch.

the blue wire is the one that should be going to the trim up solenoid.

When people are to f*cking lazy to replace them when they fail they simply connect the blue wire to the purple with white wire and it bypasses the limit switch and allows the trim or trailer buttons to run the trim pump all the time.
 
Kghost, thank you for the prompt response. I do have the mercruiser operation and maintenance manual which shows the same schematic you provided. I will chase the wiring to see if the previous owner had bypassed the trim wiring like you stated. I have come across many wiring repairs, on this boat, where the previous owner had either used household wingnuts or simply connected wiring with nothing but electrical tape (I hate back-yard butcher repairs). Thanks again for the information.

Eric
Iron Mountain, MI
 
OK, I am making progress albeit somewhat backwards. All the wiring at the hydraulic pump (for outdrive rams) seems to be as it should be without splices or bypassed. The up solenoid (for pump) has the Blue/white wire connected to it and the "Down" solenoid has the Green/white wire connected to it. So I disassembled the remote shift lever where the trim control buttons are located. I did not see anything out of the ordinary but I tried something to see where I stand. I swapped the Purple/White lead with the Blue/White lead (at connector behind remote shifter assembly). Low and behold, the "Trailer" switch brings the OD all the way up and now the "Trim Up" switch STOPS due to the Limit Switch.

Yeah...problem solved. Thank you Kghost.
 
because you cannot get a perfect seal no matter how you do it. When replacing the sender, mod the wiring to the sender so that it dosent have 12v when the key is on.
 
I'm also just coming across this thread, and hope someone can help. A boat I bought this year (Wellcraft 192) came with the trim limit senders disconnected. And I can't easily tell where they are connected to the pump. They are just laying in the back of the boat (4 butt connectors) by the trim pump. Can anyone point me to a wiring diagram that shows where they need to be attached? I looked for terminating butt connectors on the trim pump, but they are nowhere to be found.
 
The four bullet plugs dont plug into the pump, they connect to the harness from the switch (purple wire) and a blue wire which then goes to the pump. there should be a few wires out there, two go directly to the switches up at the controls to the pump solenoids, one goes from the controls to the trim limit switch then to the trim solenoid. the trim up switch and the limit switch are in series and just like the trailer switch, except that the trim switch has the sender in series. diagram: http://fuehrerscheinindeutschland.c...alpha-senders-schematic-page-1-fetch-id-d.jpg
 
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