Electrical Problem - Not Sure What

[davemoore]

While out on the lake Thursday afternoon, I started up the motor to move to a different spot and when I went to about 3/4 throttle, the engine began to bog down like it wasn't getting any fuel. I pulled back to about 1/4 throttle and it ran fine. I throttled up again, slowly, and it seemed ok, until I pressed the trim switch to bring her up, and it cut out again. I began watching the gauges and pressing the switch, and noticed the RPM's drop slightly, and the voltage drop (on the depth finder, which is much more accurate) every time I pressed the switch. Then I started trying other things - like the bilge pump - that draw lots of power and it did the same thing... like the voltage is dropping too low to properly charge the coil.

I usually have somewhere around 14-16 volts while running, but have been noticing less recently, and on this day, I was in the 11.5 range. At one point in the nights before, while using a hand-held spotlight, I noticed it drop to 10.5.

I'm not sure if my charging system is going, or if it's just a battery finally going. I don't know how old the battery is - we bought it with the boat.

What can I do to test the charging system? If it is the stator or regulator, I think I want to change to an alternator, right?

Thanks for any help.

Dave

 

[Barnacle_Bill]

Re: Electrical Problem - Not Sure What

It would help to know what motor you have. Year, size, model, etc.

 

[stonyloam]

Re: Electrical Problem - Not Sure What

470 right? Even if the battery is not the best, your charging system should be outputting around 14 volts. The stator essentially has no moving parts, and as long as the magnets are in place, failure seems unlikely. More likely the regulator, time for for an alternator conversion. I just installed the low mount w/ps from Breezeworks. Going to test it out tomorrow, if the weather holds. In the meantime you could get your battery load tested to see what kind of shape it is in. Most auto parts stores or WalMart can do it. Got to keep that old 470 hummin.

 

[txmdc]

Re: Electrical Problem - Not Sure What

My first thought is that there is a bad cell in your battery. Another thought is that you have a bad ground connection. Check the connections to your motor and to your battery. Even what seems like a little bit of corrosion can cause a headache.

As bhile said, we don't know what we're working with, but if it's an I/O that has a marine grade of a regular automotive part, Autozone should be able to test your alternator, regluator, and battery(ies). They would be a big help in finding out which parts are good and which ones aren't.

 

[davemoore]

Re: Electrical Problem - Not Sure What

Sorry y'all... yes, it's a 1983 Merc 470, all original...

I just went out and checked to make sure I had a v-pulley for the alternator conversion (which I do), and noticed that the regulator may be leaking and looks somewhat cracked (hard to tell for sure by flashlight). I will check it closer in the morning.

I think I'm going to plan on an alternator conversion and new battery.

We cut our excursion short on Thursday because I was scared we'd get stuck in the middle of an empty lake (yes, it was almost empty ).

Thanks for the input... will keep ya' posted...

(PS: Overall, I'm very pleased with the 470 - as long as you take good care of them, seems like they'll run strong and long)

 

[Jessfly1]

Re: Electrical Problem - Not Sure What

Here are some voltage tests if the problem persists. Battery should have about 12 volts with the motor not running, not close to 12V weak battery. With it running it should maintain about 14V, not 14V bad alternator (stator). When you first start the motor your battery should not drop below 10V if it does your starter is drawing to much voltage and that = bad starter.