87 Mercury 115 voltage issue

[archbuilder]

I just put my rebuilt boat in for the first time last week. I have a 87 inline 115 Mercury on her. I wanted to get her in, so a few things were a bit "unfinished" including the battery hold down. I put a couple of I screws into the transom (secast) and bungy corded the battery to it. That put the battery slight out of level, maybe 5 to 10 degrees. I charged the battery the night before, (new battery) at 2 amps. It wasn't quite to 100% when we went out but close. When I first put her in, the motor was putting out 13 volts. Later I noticed it was running at 16. I thought it might be a connection issue with the gauges....still have some issues to work out on the mount / terminal connections. Anyhow I made a note to check that out. This morning I was getting everything ready to install the carpet and pulled the battery out. Battery acid had ran out the back of it from the cells. I did some research and from what I'm reading the battery acts as the voltage regulator on these charging systems, is that correct? Sounds like you only have the stator, rectifier and battery? I'm wanting to hit the lake next weekend, so I'm excited about figuring this one out. Here is my list of possible issues:

1. Bad battery, short or weak cell
2. rectifier out?
3. charger just boiled over the battery? Its an automatic so that doesn't seem likely.
4. The angle of the battery caused the acid to run out? It was still on the battery, so maybe that is the issue?

Regardless if high voltage is an issue, perhaps I should by one of the aftermarket controllers that regulates the voltage? I'd hate to smoke an I-pod with high voltage! Has anyone had any experience with those? I'm still trying to figure out if it replaces the rectifier or supplement's it.

 

[CharlieB]

Re: 87 Mercury 115 voltage issue

Older rectifiers are just that, rectifiers, with NO voltage regulation.

Wet cell batteries will limit voltage to the maximum that THAT battery will accept. As a battery ages, this self-imposed 'limit' increases. This is normal of a wet cell battery and is NOT noticed in our daily drivers as those charging systems are regulated to reduce water loss in the battery. As long as your marine batteries water levels are maintained and the battery regularly used, a battery can last a great many years.

Fast forward to today, electronics ARE susceptible to high voltages and motor manufacturers have responded by adding regulators.

If you run electronics on your boat then the addition of a regulator is a very good idea.

The only drawback to a regulated charging system is for the OLD aging battery, with its advanced age it may need 15 - 16 volts to fully recharge, the regulator will not allow that, the UNDER-charged old battery acts like it has failed and gets replaced a year (or two) sooner than it would have on an UN-regulated system.

Not a big deal unless you are a lot cheaper than I can be (sometimes).

So it becomes a toss-up, UN-regulated for a longer battery life (and fried electronics)

OR

Regulated to shorten battery life yet save the electronics?

Note to self;
There are a LOT of old 'tinnies' out there fishing WITH electronics, old motors, and old batteries. Voltage doesn't rise till the motor is would up, you don't usually look for fish at full speed. Don't run most electronics at full speed.

 

[archbuilder]

Re: 87 Mercury 115 voltage issue

So it sounds like my battery or its monting angle might be the issue?

 

[CharlieB]

Re: 87 Mercury 115 voltage issue

It's also possible that the battery was slightly over-filled to begin with.

Car battery locations are quite level and stable so they can be filled to the max.

Boats tilt, nose high on take off, any excess acid can 'wash' up and out the vents.

As long as the acid level completely covers the plate during 'normal' operation then that is fine.

Enclosed battery boxes are very highly recommended, often required on many classes of boats by the Coast Guard. Not near so tightly regulated on small craft.

5 degrees isn't much, I'd be more inclined to believe that your battery was filled to the upper limit, then leaks a couple drops when you first slam the throttle. Keep cleaning it off, check the fill level and you will probably soon see it stabilize just under the 'full fill' level.

 

[archbuilder]

Re: 87 Mercury 115 voltage issue

Thanks I think I will try that out and see what happens. When she comes out of the hole, all you can see is sky! I should know more after next weekend on the lake.