Mercruiser 170 showing extreme voltage on meter

[glastron86]

This is my first boat, 86 glastron, have been out 6 or 8 times this summer. I just had trouble this last time out with the battery. The battery showed dead cells, I noticed the volt meter is running extremely high (16+ V) just before the battery went dead. This is the first time that I had noticed this. I replaced the battery and it is still running high. Would it be a voltage regulator? Thanks for the help!

 

[Don S]

Re: Mercruiser 170 showing extreme voltage on meter

Yes, it's most likely a faulty regulator. Running at 16 volts will destroy a battery in short order.
Normally when there is problems with the charging system it's best to locate a kit for changing from the stator/balancer-rotor/regulator to a standard belt driven alternator.
The regulator you need is 375 bucks from Merc.

 

[kcole683]

Re: Mercruiser 170 showing extreme voltage on meter

My 1985 170 Mercruiser would regularly run at 16 to 17 volts on the gauge. The battery I had in it when I sold it was 3 years old and still going strong. All you have to do is keep the battery filled with water and it should be fine.
The water cooled voltage regulator on these engines is designed to run at a higher voltage. The voltage limit before the regulator turns on to reduce the voltage is in the high 16 to 17 volt range.
I had a copy of the page from the Mercruiser manual that had the exact figures. When I sold the boat this spring I made the buyer a copy of all my info and then deleted it. Now I don't have it to refer to grr.
If the voltage regulator turns off and on I would not worry about it. When I ran my boa I watched the volt gauge and it fluctuated between 12.5 volts up to about 17, there was a definite movement when the regulator turns on and off. If the boat does this the regulator is working. if not then you may have a problem.

 

[DHPMARINE]

Re: Mercruiser 170 showing extreme voltage on meter

There also was a service bulletin about rewiring if the dash has an ammeter,not a volt meter.I've heard and not seen what Don says,but I would sure look into it.

DHP

 

[glastron86]

Re: Mercruiser 170 showing extreme voltage on meter

I am curious what would be involved with switching to a belt driven alternator, and is this something that any good boat mechanic could do?

 

[ntheyer]

Re: Mercruiser 170 showing extreme voltage on meter

Go to breezeworks.com. That is a great site for the Merc 470 engine and he sells a conversion kit inluding alternator for around 350$ if I remember correctly.

 

[captian Ozone]

Re: Mercruiser 170 showing extreme voltage on meter

mine drops after the motor warms up to 14.5 to 15 USSUALY. A dual battery isolator adds additional drop. It also sometimes goes crazy and does not charge at all for several minutes or pins and then starts working again.