Alternator – Fits Mercury 75-115 HP 4-Stroke Outboard Engines (Replaces 8M0063970, 897755T)

$167.09 $267.00

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Alternator – Fits Mercury 75-115 HP 4-Stroke Outboard Engines (Replaces 8M0063970, 897755T) is backordered and will ship as soon as it is back in stock.

Worry-free returns

You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).

If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.

Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This is a high-output aftermarket Alternator – Fits Mercury 75-115 HP 4-Stroke Outboard Engines (Replaces 8M0063970, 897755T). It is engineered to perform as a direct replacement for original equipment on Mercury Marine 75, 80, 90, 100, and 115 HP 4-Stroke EFI outboard engines manufactured between 2001 and 2020 (serial numbers 1B366823 to 2B094995).

This unit provides a reliable, cost-effective interchange for several part numbers, including Mercury 8M0063970 and 897755T, ARCO 20852, Delco 8400080, and others.

Installation Method: Belt-driven serpentine pulley
Power Output: 12 Volt / 50 Amp for robust charging
Package includes one complete alternator assembly

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Brand	Part Number
Mercury	8M0063970
Mercury	897755T
ARCO	20852
Delco	8400080
Arrowhead	ADR0313
J&N	400-12367
EMP	4-6840
Sierra	18-6840
API Marine	20126

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Designed primarily for Mercury 4-stroke EFI models from 75 to 115 HP. Please check your engine's serial number against the range provided (1B366823–2B094995) where applicable.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	75 HP EFI	75	4-Stroke	2001–2020	8M0063970/897755T	S/N 1B366823-2B094995
Mercury	80 Jet EFI	80	4-Stroke	2001–2014	8M0063970/897755T	S/N 1B366823-2B094995
Mercury	90 HP EFI	90	4-Stroke	2001–2020	8M0063970/897755T	S/N 1B366823-2B094995
Mercury	100 HP EFI	100	4-Stroke	2001–2012	8M0063970/897755T	S/N 1B366823-2B094995
Mercury	115 HP EFI	115	4-Stroke	2001–2020	8M0063970/897755T	S/N 1B366823-2B094995
Mercury	115ELPT EFI	115	4-Stroke	2001–2012	8M0063970/897755T
Mercury	115ELPT EFI Saltwater	115	4-Stroke	2004–2005	8M0063970/897755T
Mercury	115EXLPT EFI	115	4-Stroke	2006–2012	8M0063970/897755T
Mercury	115EXLPT EFI Saltwater	115	4-Stroke	2001–2005	8M0063970/897755T
Mercury	75ELPT	75	4-Stroke	2013–2020	8M0063970/897755T
Mercury	75ELPT EFI	75	4-Stroke	2006–2012	8M0063970/897755T
Mercury	80ELPT Jet Optimax	80	2-Stroke	2009–2014	8M0063970/897755T
Mercury	90ELPT	90	4-Stroke	2013–2020	8M0063970/897755T
Mercury	90ELPT EFI	90	4-Stroke	2006–2012	8M0063970/897755T
Mercury	90EXLPT	90	4-Stroke	2013–2020	8M0063970/897755T
Mercury	90EXLPT EFI	90	4-Stroke	2006–2012	8M0063970/897755T
Mercury	115ELPT	115	4-Stroke	2013–2020	8M0063970/897755T
Mercury	115EXLPT	115	4-Stroke	2013–2020	8M0063970/897755T

Technical Specs

Product Type: Alternator
Installation: Belt-driven
Output: 12 Volt / 50 Amp
Rotation: Clockwise (CW)
Pulley Type: 4-Groove, 58.5mm OD
Fan Type: Internal Fan (IF)
Regulator: Internal Regulator (IR)
Clock Position: 12 o'clock
Mounting: Earth Return
Terminal Type: B+ Terminal: M6-1.0
Dimensions: 20.5cm x 18.5cm x 18.0cm (H x W x L)
Weight: 3.5 kg (7.7 lbs)
Warranty: 12 months leisure use / 90 days commercial use
Other Technical Attributes: 5SI Unit Type

What’s in the Box

1 x Alternator Assembly (8M0063970/897755T) with integrated pulley

Installation Notes

Disconnect the battery terminals (negative first) to prevent electrical shorts.
Locate the belt tensioner, release the tension, and carefully slide the serpentine belt off the alternator pulley.
Unplug the main electrical harness and disconnect the battery charge wire from the B+ terminal on the back of the alternator.
Remove the upper and lower mounting bolts holding the old alternator in place and lift it out of the engine bay.
Position the new alternator and loosely thread in the mounting bolts.
Reconnect the electrical harness and the battery charge wire, ensuring a secure connection.
Tighten the mounting bolts to the manufacturer's recommended torque specification.
Reinstall the serpentine belt, ensuring it is correctly routed on all pulleys, then re-apply tension.
Reconnect the battery terminals (positive first). Start the engine and verify the charging system is operating correctly.

Troubleshooting & FAQ

How can I confirm this alternator fits my specific Mercury outboard?

The best way is to cross-reference your old part number with the numbers in our Part Number Matrix. Also, check your engine’s model, horsepower, and year against our compatibility table. For many models, fitment is dependent on the engine serial number falling within the S/N 1B366823 to 2B094995 range.

My engine is an 80ELPT Jet Optimax, which is a 2-stroke. Will this part still work?

While this alternator is primarily specified for the 4-stroke EFI engine family, some sources indicate compatibility with the 2-stroke 80ELPT Jet Optimax (2009–2014). If you have this model, please visually compare your existing alternator and its connections to our product images and specifications to ensure a match before ordering.

What are common signs that my current alternator is failing?

Symptoms include a battery warning light on your console, dimming lights, slow engine cranking, a whining or grinding noise from the engine, or a battery that frequently dies. You can also test the voltage at the battery with the engine running; it should be between 13.5 and 14.5 volts. A reading outside this range often indicates an alternator problem.

How often should a marine alternator be inspected or replaced?

There is no fixed replacement interval; it depends on usage and conditions. Inspect the belt at regular service intervals. Alternators in saltwater environments may have a shorter lifespan. Replace it when you notice any signs of failure to avoid being stranded with a dead battery.

What is the difference between this and an OEM part?

This listing is for an aftermarket replacement, not an original equipment manufacturer (OEM) part. It is built to meet or exceed OEM-level specifications using comparable materials. All our parts are manufactured in an ISO 9001 certified facility and are batch-inspected to ensure quality and consistency.

How fast do you ship and what does it cost?

We ship worldwide quickly, with a typical transit time of 5–15 days for most regions. Standard shipping is free. Expedited shipping options, if available for your location, will be presented at checkout.

What is the warranty and return policy?

This part is covered by a 1-year warranty against manufacturing defects under normal leisure use (90 days for commercial use). If you experience an issue, please contact our support team with your order details. Returns are accepted within our standard window for unused parts in their original condition. See our full policy page or contact us for instructions.

Safety & Important Info

Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
This is an aftermarket replacement, not an OEM component.
Professional installation is recommended for safety and performance.

About Sea Sierra

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Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
Manufacturer-Direct Value — Fair pricing without compromising on materials or quality control.

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