NMEA2000 - engine interface > SMIS connection seems intermittent

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mike.floutier's picture
NMEA2000 - engine interface > SMIS connection seems intermittent

In couple of months our Mac has been on the water we have naturally been focussing on immediate type issues so, as our outboard had been behaving impeccably, I had paid little attention to the fact that our SMIS (a Suzuki gauge designed to report a load of engine data) wasn't reporting any data at all.

However, on returning from a trip with a sailing friend, which was pretty darn exciting (15kts+ wind under full main and genoa) we were motoring slowly back to our mooring when we were passed by a RIB travelling pretty quick. My friend was helming and I , being pretty redundant at this stage, decided that we should show them that the Mighty Mac was no slouch.

Never having been faster than 5 knots under power I simply reached across to the throttle and rammed it forward. As you can imagine, with full ballast, we didn't suddenly reach 20kts and leave our competitor grovelling. I quickly realised this and returned the throttle to its former position.

Next the engine started to cycle, ie do a good impression of my friend tinkering with the throttle, like he was trying to get it to stay exactly at 3000 revs but has a shaky hand.

So I went through all the usual diagnostics for such behaviour, ie seems like a fuel issue so.....but then realised that the surging behaviour was definitely focused around 3000 revs and, on reading the manual for my Suzuki DF50, noticed that anyone foolish enough to push the throttle too far forward would simply initiate the "over-rev" fail safe which, just like the "neutral" fail safe limits revs to 3000 using the fuel injection system.

So, whilst this was reassuring regarding the state of the engine it did subsequently highlight the lack of a working SMIS gauge which, among other things reports the engine revs and also the "over-rev" caution, not to mention oil pressure, engine temp etc.

Having noticed the gauge wasn't working I tried re-starting the engine several times and eventually the gauge kicked into life and indeed appeared to be reporting all the correct info. This was pleasing until I realised that it was to be a rare occurrence.

Ok, I guess it's time for my question. I understand that everyone's boat is probably configured slightly differently BUT before I delve into the bowels (to hopefully discover a loose or corroded connection) I would appreciate any general guidance on tracing the wiring from my engine to my binnacle-mounted SMIS gauge - no other NMEA 2000 stuff involved afaik.

MacGregor 26M 2009 - Sky's the Limit -  Suzuki DF50