Mercruiser Alpha Dual Power Trim

[joliette]

I'm just starting to look at wiring up my power trim for two drives. I have a Quicksilver dual throttle control, which has the two trim switches built into one of the throttle levers. I have identified the 5 wires relating to port up / down, stbd. up / down and common. However, these wires are quite a light gauge compared with the wiring in the power trim pumps and looms, so I am concerned about connecting them directly to the trim pumps ...

Investigations so far have revealed a Mercruiser Dual Trim Control Panel, containing a couple of relays connected to a trim switch panel (that I do not need as I have the switches at the throttle). This suggests to me that I ought to install a similar relay set up with my Quicksilver dual throttle ... Is that the correct the way to go about it?

 

[spannerman]

There should be two relays on the trim pump, for up and down.
The Blue/white wire is up, the green/white is down, these wires only control the relays so don't need to be heavy duty.

 

[joliette]

Yes, I've just tried that out and it works great!

My problem now is how to wire in the Trim Limit Switch. I assume the function of this is to shut off the power supply to the trim pump. Is the switch meant to operate on both the up and the down solenoid? Looking at Mercruiser wiring diagrams it appears that it operates on just the up solenoid, but then I do not have a circuit diagram to check. If it does operate on just the up solenoid, what happens when the down extremity is reached, or is that just something to look for on the trim gauge?

 

[spannerman]

The blue/white wire goes via the trim limit switch so only works on 'UP'
There should be a 3rd wire Purple/white from the trim buttons which goes direct to the Up relay so when the trim limit is reached you can then drive the trim up all the way for trailoring. You should check the trim limit works correctly by trimming out until the pump stops and measure the length the trim cylinder has extended, it should be 20-3/4" or 520mm on an Alpha drive from center to center on the mounting spindles.
When you reach full down you will hear the pump make a screeching sound as the overpressure blowoff valve opens to protect the system, so you won't damage it if you hold the button a bit too long.
Hope this helps.

 

[rafiki_]

I have a Quicksilver (twin) throttle contol with my Alpha's. This is wired to trim the drives down only, with a separate Trailer Up switch. Not sure why, and a bit fiddly to use in practice.