Incorporating Power Tilt and Trim

[boarder290]

I have a 1978 Johnson 70 horse that currently does not have power tilt and trim. I found a tilt/trim unit which will work however i have some questions regarding the switch to operate it. The unit is two wire and from what i have read this will require a set of relays to reverse the polarity to get it to raise and lower. My question is if I can use a double pole double throw switch instead. It is the same thing as far as i could tell. Also what would the amperage rating of the switch need to be to not burn out.

 

[Frank Acampora]

Re: Incorporating Power Tilt and Trim

The tilt/trim motor can draw up to 30 amps so it really should be protected with a 30 amp circuit breaker. The breaker is placed in line with the power leads to the relays. The signal fom the switch only energises coils inside the relays so it can be protected with a 5 amp fuse. However, power for the switch is usually taken from the battery terminal of the ignition switch so it will already be on a fuse or circuit breaker placed inside the engine.

Yes, you can use a double pole, double throw switch BUT----You must manually move the lever to stop tilting. It is not the best option and you really should buy the correct type: A M-O-M switch is the accepted one. Momentary on-- Off-- Momentary on. This switch is spring loaded and returns to center (open) when you release the button or lever. It can be had at Radio Shack for a couple of dollars.

 

[metriccrescentwrench]

Re: Incorporating Power Tilt and Trim

I'd check around on ebay and see if you can find a tilt/trim relay box. If you do end up using a momentary double pole switch make sure you run wire large enough to take the full amount of current. Also, make sure that your switch is rated for DC amps - it takes a significantly more robust switch to handle 30 Amps DC than 30 Amps AC.

 

[nphilbro]

Re: Incorporating Power Tilt and Trim

Frank is absolutely correct!

I dash mounted mine with a double throw switch, which is fine...EXCEPT...be sure to get one that is self centering (M-O-M is apparently what it's called)!

I used a cheapo from Radio Shack I had in the shop not thinking twice about it. The problem is that I don't always get it back to center and it wreaks havoc if I'm paying closer attention to other things...like driving! It will also switch on its own from bouncing in big water which is very bad! As soon as I find one that springs to center I'm replacing it. Radio Shack, Schuck, Autozone don't carry them in stock.

I really like the placement, though, and glad I moved it to the dash and away from the controls.

Wiring can be a bit confusing though. I have common ground and power terminals (multiple) I wired under both the dash and at the stern. You'll want power it in a short run to the fused stern source - but I really like the idea of using a breaker for such an important component. Mine isn't switched except for the main battery Guest switch).
Run the two send cables from the T&T(green/blue I think) forward to the switch and connect to the outer terminals on on the switch and - here's where I got hung up - run the center terminal TO GROUND. I don't believe my switch is any more than 5A, btw.

 

[boarder290]

Re: Incorporating Power Tilt and Trim

Thanks for the input! I was planning on using a momentary switch. I found one on amazon that is waterproof dpdt mom. My biggest concern is why relays were used vs a switch in the original design. I read somewhere that the relays would dissipate heat, but this did not make much sense as the relays are just transferring power through them, the same as the switch would. Or did they just not use them because they were not developed yet? Being an engineer I like to understand the how, not just the why.

 

[hungupthespikes]

Re: Incorporating Power Tilt and Trim

Money drives most things. The relays and the short wire runs compared to the long 30a wire runs and the 20 dollar switch. Not to mention the safety factor of the high amps being contained in a much smaller area.

With the relays: 3-18 gauge wire to the single poll double throw switch.
without the relays: 4/6 - 8/10 gauge wire to a heavy duty double poll double throw switch.

It would be faster, safer, less money, and easier to install/troubleshoot, to use the relays.

Do you really want to use a switch in order to swap the power and the ground?
huts

 

[nphilbro]

Re: Incorporating Power Tilt and Trim

It would be faster, safer, less money, and easier to install/troubleshoot, to use the relays.

Do you really want to use a switch in order to swap the power and the ground?
huts

In my case, the entire 20ft T/T cable assembly from relay to relay was missing from the remote even though the relay plug sockets were present. By running the power just a few feet from the T/T motor to the main switched battery busbar I'm keeping the actual AMP load localized and the load at the switch is less than my 10A fuse or cheapo switch. The wire coming out of my trim motor itself is only 14 gauge.

I think they used relays because everything had to fit in the cable assembly bundle from motor to remote and running 2 dedicated 8GA cables 20ft wouldn't be practical.

FWIW...I haven't had any issues other than those stated earlier.