***Alternator mesurements for 3.7 Mercruiser mod**Not much room in engine bay**

[Lukelona]

Ok guys, cleaned all battery terminals, the better battery that was in it had bad connection this whole time. I turned switch to just the better battery and hit key, it would lose connection and is have to wiggle terminal. Put brand new marine battery from my other boat and put it in, took the crappy older battery out and put the almost new automotive battery in with the marine. Following me? Lol
took it out for a couple hours test run.
As soon as launched, checked voltage via multimeter. It was charging little above 12v
Drove it around for a while, batteries don't drain at all, but multimeter still reading about 12.3-12.5 give or take.
Well after about an hour, I had stopped for a min, then took off kinda fast and boom, the gauge shot up to halfway mark, and I stopped again (to check if something bad happened lol) and checked voltage, it was reading 13.5-14v! This is where it should be probably?
Took off again and it stayed charging good for about 10 min then slowly went back down towards where it was reading (12-13v).
So I'm lost now. Does the regulator only kick on when batteries start to drain, then kick back off? Is the regulator going bad? I'm not trying to get stranded due to low voltage lol.

 

[stonyloam]

Yeah about 14 v is where it should be. Could be the regulator terminals need to be cleaned and tightened. You need to get ahold of a Mercruiser manual, #8 tells you how to check the regulator. I can't link to boat fix on my IPad. It seems like the regulators either work or not, no in between.
Here is a little something: http://www.breezeworks.net/cgi-bin/MBoard/forum/display_topic_threads.asp?ForumID=1&TopicID=98

 

[Lukelona]

Yeah about 14 v is where it should be. Could be the regulator terminals need to be cleaned and tightened. You need to get ahold of a Mercruiser manual, #8 tells you how to check the regulator. I can't link to boat fix on my IPad. It seems like the regulators either work or not, no in between.
Here is a little something: http://www.breezeworks.net/cgi-bin/MBoard/forum/display_topic_threads.asp?ForumID=1&TopicID=98

thanks for the info, much appreciated!
I'll check the terminals for corrosion or loosened.
Also I'll try to find an online manual for the 3.7...

 

[stonyloam]

There is a site called boatfix that has manuals that you can view on line, and print (I think), I just can't link to it on my iPad. When I get back home to my PC i'l send you a link, in the meantime maybe one of the other folks can link you up. You want mNual #8 for the newer 470's, if you have an older model the regulator should be the same for either.

 

[alldodge]

I think you meant boatinfo, and if so I'll assist
http://boatinfo.no/lib/library.html

Boatfix does have some stuff but not manual 8, and those it does have there are only a few pages
http://www.boatfix.com/merc/mainmenu.pdf

 

[stonyloam]

Thanks Dodgeman, the old brain ain't what it used to be LOL.

 

[Lukelona]

I'm doing all this from my phone, so I guess I need the laptop to open the link.

 

[Lukelona]

Can I change the name of this thread? Lol

Also I un-bolted the Orange wire and cleaned the contacts with wire brush, checked the other connections for tightness and still no change in voltage.
It's reading 12.1 when I first start it cold. This is with no electronics on

 

[Lukelona]

I looked closely at engine to see if/how I'd have room to fit an alternator. I think if I use I high mount with brackets from timing cover and power steering pump and keep the alt. close to PS pump I could fit it

I'm planning on making my own brackets simply because I'm not spending almost $200 for $10 in steel lol
I can purchase a 10si marine alternator oneBay for under $60 with free shipping.
I plan on going this route asap.

In the meantime, I took the boat out yesterday and today with no issues.
If it's only charging just above 12v does this mean it's not charging or charging just enough to keep batteries charged? haven't used any accessories except radio here and there. But it starts right up strong every time.

 

[bruceb58]

It's not charging. A fully charged battery is 12.7V so ut needs to be over 13V to be charging.

 

[Lukelona]

How are the batteries not dying though?
I need a real alternator asap! Lol this thing is stupid

 

[bruceb58]

You need to measure the voltage at the battery. The gauge on the dash could be WAY off.

 

[Lukelona]

You need to measure the voltage at the battery. The gauge on the dash could be WAY off.

I have tested at battery. Both running and not running.
Not running is right about the same as running. But I've started it tons of times, and taken on the water multiple times and hasn't drained batteries at all.
This is what I don't get.
If it wasn't charging, seems like the batteries would've drained by now?

 

[bruceb58]

Ignition system is a fairly low current draw. Other than the power requires to operate the starter, you could run for a long time depending on your battery capacity.

 

[Lukelona]

Ok, yea it starts very quickly,even when cold. Within couple revolutions. So probably isn't drawing much.
I'm gonna go buy a alternator locally probably tomorrow and fab some brackets. I have an idea that I think I could fit it in my tight bilge area.
I will post pics of process and completed job. (hopefully) lol
That way, anyone with the same issue can learn from this, as that's what this forum is for right?