Spastic Alternator Gauges

[HUMPH]

So, we were heading out of a marina we spent the holiday at this morning and I noticed that my gauges were not reading proper voltage. They were bouncing around quite a lot reading down to 6 or 8 volts then up to 13 volts or so. Both were having this issue but the port side much worse. The outside temperature was in the high 40's and the wat temp was 43.5 degrees. After the engines started warming up a bit the gauges both read a steady 13+ volts. What would cause is?

 

[Lazy Daze]

Connections (alternator, battery, grounds, gauges, etc) could be dirty or more likely loose. As things heated up, the metal expanded and tightened the connection enough. I'd go through the various connections and feel/twist them looking for a loose one. Take note to condition while you're there.

If no luck, the next time it happens have a voltmeter ready to check voltage right at the battery (ies). This will at least tell you if the problem is between the alt and the battery or somewhere else... Without knowing much about your engine and how it's controlled, that could be ECM, gauges, etc.

 

[endless seas]

Had my alternators rebuilt and fixed the problem.

 

[Kon Tiki]

I am a Patriots fan, but anyways, here is my experience with that situation. Good game a few weeks back.

I have the same engines and it has been explained to me, and seen your gauge story for years now, the Cat 3126 and would assume the 3116 the same. The engines are equipped with air heaters, these are thermostatically controlled, the relays and controls are in the box mounted on the back portion of the engine. When I have a cold start the gauges are pegged all the ways to the lowest value and as the engines begin to warm up I can hear my relays clicking on and off. This would explain why when you had some heat and were at operating temperature the volts read normal. Living in the Northeast this has proven to be a daily start up event for me, in fact, I use as a sort of okay gauge on the engine readiness for line release.

Our friends from the south may never even see this event, if so, only for a very short event.
Try another cold start and watch it again, this will take at least 15 minutes at those temperatures to stabilize again.

go Pats....

 

[HUMPH]

Thanks! I figured it had to be something to do with cold weather & water. I do have these relay boxes so maybe I will open things up, start the engines and watch for what you describe just so I know that is truly what it is.

Maybe we can play again this year?

 

[Kon Tiki]

Ken,
Let's hope we meet again in the bowl. After I sent the first reply I pondered a little more about the gauges, Endless Summer seemed to be able to fix his by having the alternators tuned up. I do have a friend that has a 31 Cabo with 3116 engines, his alternators look as as big as the starter motors, my alternators look like automotive size, like my childhood 350 Chevy engine. I would assume my buddy has alternators of the higher output version. Not sure why Searay selected these for my forty footer, I have plenty of electronics and AC/DC refrigerator.

I purchased the boat from a friend, he had the boat for 3 years, no alternator replacement, I am heading into season 6 and never touch them.

Regards,
Pat

 

[endless seas]

Yes I am familiar with the heaters but after both engines were warmed up the gauges fluctuated in a different manner. Sent them to the local alternator shop and for 150.00 each the gauges are steady.
Good luck come on spring...