Mercury – Alternator | Charging System | 8M0057693

Overview

When the alternator on a Mercury FourStroke starts to get weak, you usually notice it long before it quits—electronics flicker, the battery never seems fully charged, and the engine just doesn’t feel as “settled” as it should. This alternator is built for the 135–150HP EFI models and is designed to keep up with everything these motors run: ignition, pumps, lights, and whatever gear you’ve added over the years. It holds steady output whether you’re idling through a tight channel or running hard across open water. If your battery has been dropping lower than usual, this is the kind of part that brings the system back to life.

Key Features

 • Charging Alternator – Keeps the cranking battery and onboard systems supplied with steady power.
 • Built for 135–150HP EFI FourStrokes – Matches the output and mounting used on these engines.
 • Heat-Tested Design – Verified to hold up inside a hot outboard cowling.
  • OEM Fit and Output – Meets Mercury’s charging specs for reliability.
 • Stable Voltage Under Load – Helps prevent dips when multiple accessories are running.

Engine & Boat Compatibility

 • 135HP EFI FourStroke
 • 150HP EFI FourStroke
 • EFI charging systems
 • FourStroke platform

Performance & Practical Benefits

A good alternator keeps the whole boat feeling solid. Starts are quicker, lights stay bright, pumps don’t bog, and electronics stay steady even when you’re bouncing through chop. The ignition system holds a cleaner rhythm too, since it’s not fighting low voltage at idle or low RPM. It’s the kind of upgrade that doesn’t show off—but you feel the difference every time you turn the key.

Why Buy OEM

OEM alternators match Mercury’s mounting, output curve, and durability expectations. They’re built to handle the heat, vibration, and long run times that marine engines see. With aftermarket charging parts, you’re often rolling the dice on voltage stability. OEM keeps things predictable.

FAQ

Q1: What’s the most common sign the alternator is going bad?
A: Electronics dimming, weak battery recovery, or slow cranking after a day on the water.

Q2: Does installing this require any computer reset?
A: No—bolt it in, hook it up, and the motor manages the charging system automatically.

Q3: Can heat inside the cowling cause charging issues?
A: Absolutely, which is why this alternator is tested to handle high temperatures.

Q4: Should I inspect the belt at the same time?
A: Yes—if the belt looks shiny or cracked, replace it while you’re already in there.

Q5: What happens if the alternator output drops too low?
A: Batteries don’t recover, electronics flicker, and the ignition may stumble at idle or throttle-up.

• Supersessions
  8M0065239, 8M0065239