Smis problems on twin df300's

[Rwloope]

My port side smis guage (2008) stopped working suddenly. It shows no data just ---
Starboard is working fine and the center guage only gets info from starboard. Center guage won't show trim level, fuel burn or anything from the port engine. I checked all connections and pulled out and reconnected all the T's. Any suggestions? Thanks

[Moonlighter]

Did you check the connection between the port engine interface cable and the engine harness? When you look at this connection, unplug the interface cable from the engine connection and check all the wires and the pins for corrosion and good connections. Have seen cases where water has got into the connections and caused corrosion.

Check the wires where they go into the back of the plug, give them a wriggle and check if they are not broken or corroded. You can go into the plug from the pin side, lift a tiny tab, then pull each wire out from the back if you want to check/repair the connections or clean corrosion out.

The symptoms you have suggest one of 2 things:

1. No communication between port engine and the network, which means

(a) a cororded or broken connection at the interface/engine harness connection point as mentioned above, or
(b) a failed interface cable or
(c) a failed T piece connecting the port engine interface to the network.
(D) a failed T piece connecting that SMIS gauge to the network.

Any of these can happen. The corrosion or T piece failures are the most likely, although it is not unheard of for an interface cable to fail as well. I would start with T pieces. Are they the old blue Lowrance ones? Those are a bit prone to corrosion related failures.

You can check and clean the connections as described above, swap T pieces between the starbord andport interfaces and see if the problem moves with the T piece, or swap interface cables and again, see if the problem moves with the cable. Those processes should help you figure out where the problem is.

2. A failed SMIS gauge. I doubt if it is this, because the fact that you cant get any data from the port engine to display on the other gauges points to one of the problems mentioned above. The 3 lines indicate that the gauge is getting power but is not seeing the network. Just double check that you definitely cannot get any engine data such as RPM from the port engine to show on any of the other gauges. If you end up being able to get port engine data on any of the other SMIS gauges, then the culprit will most likely be a faulty SMIS gauge.

Good luck with your trouble shooting, let us know how you go.

[Rwloope]

Thanks for the info moonlighter. I checked everything and now it's in the hands of my local dealer. It turns out the other guages started doing the same thing my next trip out. I'm thinking now it may be related to a short somewhere because my starboard engine with a good alternator isn't charging and I have a big power draw coming from somewhere. I'll update when I get it back from the shop.