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2006 Opti 150's - smartcraft wiring harness problem, it's making my engines parallel all the time

L

leaky

Regular Contributor
Hi,

I've got a set of 2006 150's and smartcraft tach's/speedo setup.

The engines each have their own battery and on/off switch and are intended to be on isolated circuits. In a round-about way I found one of them had popped a fuse - trouble-shooting that further I found through the wiring harness the engines/starting-batteries are getting paralleled. So basically if you only turned one battery on, and tried to start or trim the engine with it's battery off, you end up feeding that engine through the other engines wiring harness (and popping the fuse). Similarly if you had a half dead battery and hit the starter, it would probably popped the fuse on the opposite engine.

A side effect of this is the batteries are parallel anytime the engine battery switches are on, and therefore voltage reads the same (or if one batteries dies then both end up the same).

Trouble-shooting the source of the problem - there is a smartcraft hub where the gauges are fed and engine wiring harness's for gauges plug in. It's within that hub that it's paralleling the engines - by disconnecting one engine from the hub the issue is resolved; by resolved I mean the engines are isolated and I can't feed power through the opposite engines harness anymore, but then the gauge for one engine has no signal inputs (but does turn on and has power fed from the other engine).

I did also try just disconnecting the speedo (which has signal from both engines going into it and was where I thought the problem was) but that does nothing, so it's the hub that is causing the problem..

Is this a setup problem, like for twin engine installs is there something that should have been done differently?

Theoretically I could figure out what the power feed is into the smartcraft hub, cut that for one engine, and similarly cut it on the gauge side, then connect those two together (so the power for one of the engines goes around the hub and directly to it's gauge). Any idea what color wires I should be hunting for?

Trying to figure out the "right" way to fix this before it finds a way to leave me stranded, destroys something, or starts a fire.

Thanks,

Jon
 
Last edited:
Update on this.

Reading the install manual, it states to disconnect the power for the can bus at one engine for a twin engine install, which I guess is basically what powers that "hub" I'm speaking of.

Initially I figured this was just not done, however upon inspection I found the entire 5 pin connector was disconnected on the port engine (although the manual says just to disconnect a 3 pin connector that is supposed to be located closeby to that, in effect this should also do the trick)..

Just to verify what was going on better, I took the engine harness off the hub and plugged it directly into that engines tach. It 100% works as you expect at that point with no paralleling of the engines. What makes no sense is the thing that powers smarcraft I think is what's disconnected back at the engine, so I don't understand where the power in the gauge harness is coming from.. The same reason it can power up the gauge is the reason why putting it into the hub causes the problem I think.

Any ideas or can anyone shed some light on the pinout for the plug that goes into the tach or what may be wrong?

There are a million purple bullet connectors within the ignition and gauge wires (guessing for hooking up accessories) and what I suspect is someplace one of these is putting power where it shouldn't be (like should not be plugged in but is) and/or the pinout for the connector that gone es into the gauge is wrong.

Does anyone know if the orientation of how things are plugged into the hub matters? For instance if you moved all the plugs 180 degrees around would it matter?

Thanks,

Jon
 
is a smartcraft hub where the gauges are fed and engine wiring harness's for gauges plug in. It's within that hub that it's paralleling the engines - by disconnecting one engine from the hub the issue is resolved;
Click to expand...
There must be a jumper w/in the hub providing power from one engine for both sides of the hub...that is why one harness was disconnected. Cut the jumper and connect both harnesses.
 
guyjg said:
There must be a jumper w/in the hub providing power from one engine for both sides of the hub...that is why one harness was disconnected. Cut the jumper and connect both harnesses.
Click to expand...

Thanks for the input - how would I find that jumper? As far as I know I can't get into the hub, or is there a way to get in there?

Did some more playing around last night and something else I noticed (which is a feature of the setup somehow) - if I disconnect the port ("slave") engine from the hub, and I only turn on the port engine's battery, but I do not connect that part of the gauge harness into anything, my key switch functions for that engine works fine but the power tilt does not...

If you just connect the gauge harness into the hub, but do nothing else (so only port engine battery is on), then the power tilt runs.

So somehow when you connect the gauge harness into the hub, the power tilt circuit gets fed. Since I can't imagine there are that many power leads coming up in the engine harness, it must be whatever feeds the key also gets routed into the hub, and then within the hub it also combines that to the power trim circuit. This has nothing to do with the key position either, the power trim either works or doesn't regardless of the key position, so it's a feed on the engine side of the key that must get into the hub.

There are purple and red wires going into the hub, is it probably one of those? Any light that can be shed would be much appreciated. One thing I wonder is if Mercury just intended it to work this way.

Jon
 
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