High voltage reading on bass boat (14-16v)?

Question

I have a 1990 Sprint Bass boat with a 1990 Mercury 115 hp outboard. I bought it a couple of months ago. The voltometer always reads high (14v) and gets higher when the motor is running (16v). My dept finder also gives me a high voltage warning.

All of the electonic (starter, guages, lights, bilge, aerator, trim motor) are wired to the starting battery. The trolling motor runs off of it's own battey.

Any idea what could be causing this? Bad battery, wiring?

Please give me ideas of what I can check.

Answer 1

do a basic voltage check on the battery with the engine running.  dash gauges sometimes go bad.  over-charging usually means a bad battery, but could also mean a bad rectifier or stator.  go for the battery first...it's cheaper.

Answer 2

Time to replace the batterys as 1 is bad an demanding the high charge but won't except it >Can't you smell the acid boiling>???An a very hot battery to touch>

Answer 3

Sounds like the voltage regulator is failing.

Answer 4

I'll give you the exact answer to your question because I've already been there, seen it, done that with a 1989 Merc 115; and spending a little money on it now will save you a lot of money in the future.

Getting right to the answer - the problem is your voltage regulator because YOU DON'T HAVE ONE - but you need to get one.

I bought mine new in 1989 and quickly noticed the battery voltage going unusually high on the first run.  Being an electronics technician and pretty fair mechanic, I called the dealer's service department and told them my voltage regulator didn't seem to be working.  That's when I learned that (from day one) Mercury/Mariner and Johnson/Evenrude never put voltage regulators on any of their outboard motors under 150hp until around the mid-90's.  The dealer assured me "don't worry about it, the battery will self-limit the voltage - BS!

Because of a stator's lower output (as compared to a self-contained alternator), outboards have historically been terribly lackluster in keeping a battery charged in boats that had more than just a few simple auxiliary electrical devices.  More often than not, constantly running a few electrical devices would pull more from the battery than the stator could replace even with the engine constantly running; the result was years of gripes and complaints about not being able to use a lot of electrical accessories without draining the battery. Since there was never a problem with too much charge current from a stator, there was no need for a voltage regulator, so none were ever installed.

The problem was solved in the mid-80's with a new high-efficiency stator that had almost twice the output of the older ones; but the mindset of never having enough charge current kept the outboard manufacturer's from considering the addition of a voltage regulator.  All of your electronic equipment (radios, depth finders, etc.) have their own internal voltage regulators - but your motor doesn't.

After a few years of running at very high battery voltage, the motor's rectifier went out ($200 plus labor), then the solid-state ignition/switching module went out ($500 plus labor).  It was then that I learned that all the outboard manufacturer's had come out with a voltage regulator kit that was highly recommended to be installed on all outboards manufactured from the mid-80s to mid-90s.

The regulator kit was a couple of hundred bucks plus installation, but it would have saved me a bundle of money if I'd known about it before the high voltage fried some very expensive parts in the motor - grrrrrrrrr.  So, I'd strongly advise that you get a regulator kit installed by a reputable outboard shop before it costs you dearly in the very near future.

Answer 5

most charging equiptment will charge at 14-16v. when operating under full load. all of your equiptment should be fuse protected. unless you have had a blown fuse there should be no cause for concern. is your depth finder fused? if so the fuse would blow on an overload.