Recurring gauge problem - 525EFI
 

A few weeks ago, I replaced the long block on my port motor (525EFI). My boat has SmartCraft and analog gauges as well. When the motor went back in the boat, the gauges (water temp, oil temp, oil pressure and the tach) were not operating properly; they would show some values but they were way off. The SmartCraft was reading properly and showed the engine working properly as well; RPM, temps and pressures all right where they should be. We checked all of the grounds thinking that was it. We then swapped the harness for the analog to digital interface with the center engine and all of the gauges then worked properly, so the assumption then became that the analog/digital interface module had gone bad. I replaced that module and everything was back to working properly and I had the boat out a few times and everything seemed to be fine.

Yesterday, on the first start of the port engine, the gauges were all not working again. I cycled the key and the motor on/off a few times, still nothing. Tried swapping the harnesses again to the center engine and the gauges started working, so once again the analog / digital interface appears to be the culprit, but it's brand new... seems to me that something is taking out this module or something else is going on.

Any ideas on where else to look?

Four things take out electrical items:

1. Low voltage
2. High voltage
3. Amperage
4. Inadequate ground

An inadequate ground will cause a high amp condition, so these two work hand in hand. See what the manufacturer recommends that the amperage is for the interface module. Put that sized fuse on the power side of the module. Then work from there.

Hope this helps

What did you find on this? I have an oil pressure gauge that works perfect at startup then slowly goes to zero, gauge replaced and same thing happening. Oil pressure is good have run it for hours this way. Sometimes my Tach goes haywire too zeroing out and flipping around then works fine.

Tried like crazy to find a loose ground and couldn't. It turns out that the first analog/digital interface module that I used was not the correct module for the 525 so it's possible that was the problem although it did work fine for a few weeks. I replaced that module with the right one for the 525 and thats been working properly the last two weeks. Unfortunately, season is over for me at this point, so I won't know for sure if its fixed until next year unless of course, it quits on me during my winterizing.

Thank you for the response. I will double check for loose ground but in my head it's either the wire harness you replaced or a sensor.

Not likely to be a sensor if you're having trouble with the tach and the oil pressure gauge. More likely to be a ground or the interface. If you have SmartCraft, there should be one analog/digital interface for each engine. It's easy enough to swap them to see if the problem travels. You just unplug and plug it into the other one. If the problem goes away, the interface module is likely the culprit.

both those wires run thru your main engine harness,,,pull apart and clean...maybe spread pins for a tighter fit,,,vooooodo rob

Thank you I will give that a try before throwing parts at it.

Reviving this thread. I replaced the AGI box on my port motor at the end of last season and all has been working fine until yesterday. Ran the boat all weekend and no sign of any trouble. Yesterday, start the port engine and the tach, oil pressure, oil temp and water temp gauges are not working; all of those are controlled by the AGI box. Smartcraft shows everything on the engine working normally. Get back to the dock, swap the AGI from the center engine and problem travels so again, so I know the AGI box has failed. This is now the second one now to go on that engine. It worked fine on Sunday, boat was put away and then yesterday just didn't work. Batteries are shut off when the boat is put away, so just don't know how something like that fails when nothing is being used. Any more ideas ?

Where are the AGI boxes? Can they be anywhere in the boat, behind the gauges, or on the engine? Any pics? Im still having the issue with my oil pressure gauge. Gauge reads low, then trails off to zero. I replaced the gauge and all wiring in the gauge cluster. Its crazy that you have had this happen twice.

Yesterday, I blew another one of the AGI boxes on that same motor. All three motors have these boxes. The starboard and center motor have a CAN bus wire that runs from the dash to the back of the motor right by the ECM and have a plug that looks exactly like the plug on the AGI. The port motor (with the problem) has a "terminator" plug on the end of it near the ECM rather than plug into the harness. This is the second time in a week; something is definitely wrong. Any ideas on how to trouble shoot this?

I have a similar problem, port 600SCi runs, but no gauge operation, going to swap the Analog interface module and see if problem goes to SB engine

Rob,
Did you ever figure out what the problem was?
Thanks,
Dean

That was on our 353 Formula I sold the boat and the next owner fixed it by changing AGI box.

Thanks for the data Rob!

so my AGI's are Part Number 892486A02, but I can't seem to find them on the web...

Genuine Mercury & Mercruiser parts. Analog Gauge Interface Digital Engines

This is all I can find? Plus I just need the AGI, no the harness also...
Thanks,
Dean

Back in 2014, I spoke with Mercury extensively about this problem and they had told me that they had instances of voltage spikes caused by drive trim pumps and had recommended I put a transient voltage suppressor on the drive trim pump. At the time, all of my 12V accessories including drive trim, trim tabs, etc, were all connected to the port engine battery and the port AGI was the one failing. I installed the TVS and and guess what, I blew another AGI after that. My ultimate solution was to install another battery and run a dedicated circuit to isolate all 12V devices and limit the engine batteries to just starting the engines. I have not had another AGI fail since and that was 3 years ago.

H5,
Thanks for the input, hopefully I won't have to go to the same route as you, I hopefully will get my new AGI ordered today, just need to confirm if the part number I have is correct....

I researched the AGI box thru Livorsi

Rob,
I talked w/ "Marty" at Livorsi, and we couldn't figure it out, I Bing'd it, and Hardin marine had the data, ended up calling Merc racing, talked with "Allen"and found out that I can't just buy the AGI Module anymore, NOW I have to buy the whole installation kit, P/N: 892486K04...... which has the AGI module in it, along with crap I don't need, gotta love Merc racing! :(

Of course, why not! Before you could just buy the AGI box, r & r it and away you go. I did it 2 years ago on the current Fountain, there was 2 box styles (black engine and blue engine style) to choose from but looks like things have changed.

Update, so the 892486K04 kit came in,

Genuine Mercury & Mercruiser parts. 892486K04 AGI Kit Mercury Racing


and I installed the AGI module, (different P/N than what I had installed) fire up the port engine, and all gauges work now... I now have a spare AGI I/F harness.....
Thanks for the help OSO brothers! :)