Logo
FULL SITE MENU

1986 Mercury 45 Classic 50 overcharging battery

B

BrandNewBoating

New member
Hi all this is my first ever boat. 1986 mercury 45 classic 50 on a 1987 bass tracker. I've noticed that when I'm running WOT for an extended amount of time (5 minutes+) my battery level goes to 18V. I've read alot of posts that say anything above 14V is bad. I replaced the rectifier with another one assuming it was a bad rectifier/regulator but that did not solve the issue. It still puts out 18V when running. Thoughts on the issue? It might be that the rectifier part of the circuit is good but the regulator is not doing its job.
 
I am pretty sure you have an unregulated system That means you only have a rectifier not a regulator, those motor use the battery as the regulator. So the voltages you are seeing could be normal. Make sure you don't use sealed batteries, because you will need to be able.to fill it.
 
flyingscott said:
I am pretty sure you have an unregulated system That means you only have a rectifier not a regulator, those motor use the battery as the regulator. So the voltages you are seeing could be normal. Make sure you don't use sealed batteries, because you will need to be able.to fill it.
Click to expand...

Thank you! Is the 18V safe for my fish finder? It's a Garmin striker 4. The ratings on the sheet show it as 10V-20V with a 1A limit.
 
WOT for 5 minutes! You think that's an electric motor!

You can install a voltage regulator to cure that problem. (Done several.) CDI makes one that doesn't mess up you tach readings.

Jeff
 
Is running WOT bad? I've heard its fine for older 2 strokes. I hope it's okay because its about ~30mins of WOT to get into the bay from the harbor. I'll look into CDI for a regulator. Thanks Jeff!
 
It's called...MERCY! You gotta "breath" the motor--even racers have to do that. Give the poor thing a a little mercy.

Case in point... My buddy has a 20 foot party barge with a brand new 10 hp 4 stroke Merc on it. Soon as he clears the dock it's WOT until gets to his location. Asked me to take a look at his motor since it had "lost power" after running the poor thing like that all summer.

A bit less throttle--his boat wouldn't go much slower at 3/4 throttle--and that poor motor would still be okay. Instead, it needs a complete rebuild with a bore and etc.

Hope that 'splains it.

Jeff
 
After 50 years of deep marine work I have great respect for equipment. I only run full bore to get on step. If step in "not applicable" back down to 75/80 percent power and change speeds. I now for the first time, have noticed a fellow tech to bring this up......thanks.
 
Gotta call hockey on this as got a ton of Bass fishermen I service that run wide open(WOT) for 10-15 miles during tournaments. A lot of these motors are 15-20 years old, ran like this since purchased and still run great. I myself run WOT for miles and never had to rebuild one.. I suspect your buddies was lugged to death.
 
I had to switch to a sealed battery so I installed a Mercury regulator part Nr. 88825A7 following this diagram, this limits the voltage to 13.5 even wide open.voltage reg.jpg
 
Good idea, not sure if that will effect life of the alternator. I use 2 strokes, get 50 plus years on 'em. Not sure what controls newer 4 strokes life. Correct me if I'm wrong, but 4 strokes, by design, tend to last more hours anyway when properly operated and maintained. We service a bass tournament in International Falls MN and these guys have really new stuff. Yes speed is critical here too as the tournament area is quite large.....pretty decent paychecks, lots of sponsors. So at 50 mph you travel 10 miles in about 12 minutes? That's not bad for a new 4 stroke. They BETTER be able to handle that for 15 grand a pop, eh?
 
Last edited:
Back
Top