Mercruiser 3.0 -98 charging problems

[JayEll87]

Good day from Scandinavia I recently purchased a boat with a Mercruiser 3.0 -98 with Alpha one gen 2 sterndrive. I've done full mantenance to alpha and now started with the engine. Main issue at the moment is that it's not charging correctly, recent owner replaced the alternator and things should be good from that point of view but still multimeter shows just 8,8V in both batteries.. and yes both batteries are died and I've not had time to replace them yet as I noticed this issue just two days ago.

Connections seem to be as wiring diagrams show, only difference from alternator side is that I've 2 wires connected to the same "port" in addition to purple wire, but if I've understood correctly this is just an excitation lead so it should not matter. I tried to measure pretty much everywhere but could not get anything over 9V when engine is running idle, also directly from alternator orange lead. Soo, what would this tell to experts? Can battery affect like this or could the alternator be the reason? It has less than 10hrs in it..

 

[Bt Doctur]

can you post a pic of your alt

 

[JayEll87]

Not the best pic but something I had in my phone..

 

[Bt Doctur]

cant tell what ypre but have never seen any other wire but "sense" and "excite" try removing the red wires and retest.
You should see 12v on 1 and 12v with the key "on" for the other lead

 

[Bt Doctur]

 

[alldodge]

Someone has added more wires to the 12V switched lead. The one on the left. What do they go to?

Check the to see if you have 12V on both of them with the ignition ON and running

 

[JayEll87]

Thanks for answers. I've a doubt that red wires go to stereos / tv which were not originally even an option for this boat model (year 1975.) The guy who sold the boat did not seem to be a technical mastermind so I think I can expect pretty much everything from him, he told that he had added stereo/tv by himself.

But I will re-check this and let you know what I find.

 

[TurtleTamer]

Is that a fuse connected to the main wire ("250V")? Is continuity good through that?

 

[alldodge]

Is that a fuse connected to the main wire ("250V")? Is continuity good through that?

That;s not a fuse its a noise capacitor

 

[JayEll87]

Did some research and problem is now solved. Red wires connected to switched lead were for running hour meter and engine space blower, I didn't disconnect these as I doubt that this wouldn't solve the original issue.
I measured every point from brand new battery to alternator and used engine ground point for grounding, 12,7V everywhere where it should be. Then I changed ground to alternator ground lead and lost the voltage, found out that cable was cut, replaced it and now I've 14,7V in battery terminal when engine is running Thanks for ideas all!

One issue I still noticed is the voltage gauge, which shows only 12V no matter what multimeter shows. Where does this measure the voltage? I probably place new gauge / wires to this as it would be nice to have correct readings when cruising in archipelago.

 

[alldodge]

The helm gauge is taken from one of the purple wires off the key switch