Help, I'm currently working on my trim switches on my F311. After pulling all the wires off the trim switches I then tried each wire to a hot wire to see what wire powered what. This is what I found, there are three basic colors in the wiring harness going to the Mer. control box . There are the purple wires that go to trim senders, the three light blue wires that make the drives go out and the three green wires that make the drives go in. The problem I don't understand is that it dos'nt mater witch green wire I power up out of the three they all power both drives the same time down. With the light blue ones one wire powers the drive out the other powers the other drive out and the 3rd wire powers both the drives the same time out. I'm not sure that even if the one blue wire power both drives the same time is correct. But I know that all three of my green wires shouldn't act the same way working both drives at the same time. Sorry if this sounds confusing, any help is much appreciate. Propwash

Not sure what you're after, but here's the wiring diagrams if that helps?

Thanks for responding Ghostrider. This is what I'm working on, do you happen to know what the three electrical units are and what there purpose is in this control box? Do you think I could bypass them if I can get the drives to operate the way I need them too with out any limit switches involved? Thanks Propwash

I run without the limit switches purely because when I was doing my wiring I got fed up with all the wires and did away with them! So long as you have a good idea what you're doing and you know they aren't there you should be fine. Me? I'll probably wind up putting one of those stick on labels by the trim swtiches to remind me not to screw everything up!

From what I can gather, the control box simply acts as a junction box for the relays. The relays are powered by the trim switches (which the round thing in pic 2 is) which get's it's power from the supply side of the ign switch.

There really is no point in bypassing this function as it is the correct way to wire (via relays). You could replace the function by putting in your own suitable relays but the trim limit function is controlled by the large box by cutting power to the output side of the relay thus stopping the drive. If you were to do away with the limit senders and just hard wire the trim, it is conceivable that this is then made redundant.

Long story short; pop a couple of powered 3 way relays in the line which are turned on and off by the action of the powered switches. (1 way=up, 1 = off, 1= down) If that works the drives then good! risk is without the balance provided for elec output of the one box providing override and power control, one drive may be slightly quicker than the other which may cause problems if you have a tie bar or the like.

God I hope I'm right here, or my drive's going to suffer big time!!!

The built in check valves should minimise the damage you can do if you slightly over-trim accidently, but there is no check valve for stupidity so mistakes can happen.