2014 Mercury 150 Fourstroke Alternator / Charging

2014 Mercury stopped charging last weekend.

Step one, see if I can do it myself. I’m baffled.

I checked the fusible link as best as I could. Visually it looks fine. With it still connected I read zero ohms resistance from the alternator stud to the stud on the other end of the link. Not sure if I have to disconnect it to get an accurate reading but it seems like it is good.

The alternator looks easy enough to remove. Putting it back together looks like the tough part because I do not see a belt tensioning mechanism. The alternator is held on by two bolts that look to be non-adjustable. The other end of the belt goes directly to the flywheel which isn’t adjustable.

Anyone know how to remove and replace the alternator belt on these motors?

Secondly, was my test of the fusible link valid or does it need to be disconnected before testing?

Although it reads zero, I would assume it’s good also but it’s much cheaper to pull it out and make sure.

I really can’t help you on the tension of the belt but sometimes there’s a slot behind the alternator bolt hole to swing the alternator in and out. You would need to see the back side of the bolts to know if this is the case.

Looking up the alt in the Merc parts catalog, it appears there are three points to secure it (If I have the right motor)

https://public-mercurymarine.sysonline.com/Default.aspx?sysname=NorthAmericacompany=GuestNA_KEY=NA_KEY_VALUElangIF=englangDB=eng

The link takes me to the login page. Just google Mercury Parts and make sure you’re going to the genuine Merc parts site.

There is a thread about this on walleye central: https://www.walleyecentral.com/forums/showthread.php?t=685296

One post reads as follows: “There is no idler pulley on the 150 4S drive belt. The belt is stretch to fit. To remove alternator remove the rear alternator screw, loosen the alternator front screw slightly and push alternator towards front of engine to unload belt for removal. Note that the alternator bolts are torqued to 36 ft-lbs at the factory and I don’t believe they used LocTite on them. Re-install by reversing this procedure. There is a regulator which appears to be internal to the alternator.

Merc suggests the first thing you should check if voltage at battery appears low and connections to battery are known to be good is to connect a digital volt meter between the alternator’s output stud and a ground on the alternator. This should also read battery voltage- same as when you measured the voltage at the battery- and if not look for a bad connection or break in the engine’s wiring harness before repairing/replacing alternator.”

As far as the fusable link, you need to disconnect it and check for continuity. If it is blown you need to find out why or it will happen again.

Sounds like that back bolt is slotted. I couldn’t see a slot there but I’ll give it another look.

Been busy the last two nights so I haven’t had a chance to disconnect things and recheck. Maybe tonight.

Thanks for all the help.

Based on that experience I went for it, even though I couldn’t see an adjustment slide. Blind trust.

Turns out there is no adjustment. It is fixed in place with two bolts which matched what I could see. I haven’t worked on stuff in years and did not expect this. Don’t know why anyone would design such a mess.

There was also blue Lock Tight on the two mounting bolts.

Luckily the bolts are fairly long my hope is that there will be enough play when remounting it to slip on the belt then have everything tighten up along with the bolts.

So the belt must be an exact fit because there is no tensioning the alternator on this thing.

Found a place near home to have it rebuilt and expect to have it back in a week.

Update.

Picked up the repaired alternator last night. $80.
From the tech.
It is a common design alternator with really cheap parts in it. He tried to find me a better replacement but could not find anything that matched up the mounting holes to the main shaft.

Had 1 dead diode on the negative side. Said they were cheap diodes that are not very reliable. They try to upgrade them to something more reliable if possible. There wasn’t enough clearance to put in a better diode.

It’s a 55 amp alternator. The diodes are rated for 35 amps. He did squeeze in a 40 amp rated diode although still not a dependable make. Hopefully that will help it last.

I don’t know how Mercury/dealers in good conscience can charge $300 for a replacement when the cost to manufacture in Asia is probably less than $40. Knowing that it is designed with crappy parts to begin with. What a scam.
No wonder you see them on other sites for $100. They are still making a healthy profit at $100.

Re-installation:
After trying multiple ways to install it with and without the belt, I think I finally found a way that worked.
Install the inside bolt with the alternator in place without the belt. Leave it loose.
Swing the alternator out away from the motor.
Install the belt.
Swing the alternator back to its fixed position with the belt on. Not an easy task because you have to stretch the belt a bit to get it to swing back into place.
Then while leaning on it to put pressure on the belt, install the second fixed bolt.

Don’t forget the blue Lock Tight like I did. Now that I think I have it figured out it should go back together more easily when I do it again tonight with the Lock Tight.

Going through the same thing right now. There is a hex stud near the top bolt. You can put a 15mm socket on it for leverage when tensioning/rebolting.