SKU: 48210689028

Water Pump Repair Kit – Fits Mercury 9.9–20 HP 4-Stroke Outboards (Replaces 8M0135821)

$51.30 $57.00
Save 10%
No.2 Bestseller on prudentsource.com >

Pay in installments of $14.25 with ShopPay, AfterPay and Klarna

Shipping Estimate
USA
  • USA
  • CAN

Ships within 48 hours · Estimated delivery Aug 7 - Aug 12

Promo Codes Available:

For Your Every Summer RSVP, with Code: SUMMER15

Description

Water Pump Repair Kit – Fits Mercury 9.9–20 HP 4-Stroke Outboards (Replaces 8M0135821)Water Pump Repair Kit Fits Mercury 9. 920 HP 4 Stroke Outboards (Replaces 8M0135821) This water pump repair kit is designed for Mercury 4 Stroke 9. 920 HP outboard engines with serial numbers 0R833820 and above, including ProKicker and SeaPro models. It provides a direct replacement solution built to meet or exceed original equipment manufacturer specifications. Replaces the following part numbers: Mercury Quicksilver 8M0135821, 98 8M0135821, Mercury

Water Pump Repair Kit – Fits Mercury 9.9–20 HP 4-Stroke Outboards (Replaces 8M0135821)

This water pump repair kit is designed for Mercury 4-Stroke 9.9–20 HP outboard engines with serial numbers 0R833820 and above, including ProKicker and SeaPro models. It provides a direct replacement solution built to meet or exceed original equipment manufacturer specifications.

Replaces the following part numbers: Mercury/Quicksilver 8M0135821, 98-8M0135821, Mercury 8M0137849, and Tohatsu 3RS-87322-1.

  • Engineered for a direct fit to the lower unit for straightforward installation.
  • Produced to meet Mercury Marine original equipment manufacturer specifications for reliable performance.
  • Complete kit includes the essential components for a water pump service: impeller, upper/lower housings, and plate.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Brand Part Number
Mercury / Quicksilver 8M0135821
Mercury / Quicksilver 98-8M0135821
Mercury 8M0137849
Tohatsu 3RS-87322-1

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Brand Model Rated HP Stroke Years OEM Part No. Notes
Mercury 4-Stroke Outboards 9.9 4-Stroke Serial numbers 0R833820 and above 8M0135821 Includes ProKicker and SeaPro models
Mercury 4-Stroke Outboards 10 4-Stroke Serial numbers 0R833820 and above 8M0135821 Includes ProKicker and SeaPro models
Mercury 4-Stroke Outboards 15 4-Stroke Serial numbers 0R833820 and above 8M0135821 Includes ProKicker and SeaPro models
Mercury 4-Stroke Outboards 20 4-Stroke Serial numbers 0R833820 and above 8M0135821 Includes ProKicker and SeaPro models
Mercury 2-Cylinder (333cc) 9.9-20 4-Stroke - 8M0135821 For 2-Cylinder 333cc engines

Confirm your engine model/year in the table below.

Brand Model Rated HP Stroke OEM Part No. Notes
Tohatsu MFS 15 4-Stroke 3RS-87322-1 Cross-reference to Mercury 8M0135821
Tohatsu MFS 20 4-Stroke 3RS-87322-1 Cross-reference to Mercury 8M0135821

Technical Specifications

Specification Value
Product Type Water Pump Repair Kit
Installation Direct replacement, requires common shop tools
Connection Direct fit to lower unit
Dimensions Weight: 0.63 lb (0.29 kg)
Length: 4.25 in (108 mm)
Width: 4.50 in (114 mm)
Height: 6.25 in (159 mm)
Weight 0.29 kg (0.63 lb)
Other Technical Attributes Produced to meet Mercury Marine original equipment manufacturer specifications

Package Contents

  • 1 x Water Pump Repair Kit Assembly (Replaces 8M0135821)
  • 1 x Water Pump Impeller
  • 1 x Upper Housing
  • 1 x Lower Housing
  • 1 x Plate

Installation Guide

  1. Disconnect the battery and shift the outboard into neutral.
  2. Remove the propeller and drain the gearcase oil.
  3. Unbolt and carefully lower the gearcase from the drive shaft housing.
  4. Remove the old water pump housing bolts and lift the housing assembly off.
  5. Clean the mounting surfaces and inspect the driveshaft for any wear or damage.
  6. Install the new gaskets, plate, and impeller, ensuring the keyway is aligned.
  7. Lubricate the inside of the new housing and impeller with grease.
  8. Install the new housing, ensuring the impeller vanes are turned in the correct direction (clockwise).
  9. Tighten the housing bolts to the manufacturer's specified torque.
  10. Re-install the gearcase, making sure the water tube and shift shaft align correctly.
  11. Refill the gearcase with fresh oil and re-install the propeller.
  12. Reconnect the battery and test the engine in the water, verifying water is exiting the tell-tale port.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my Mercury outboard?

A: This kit is designed for Mercury 4-Stroke 9.9–20 HP outboards with serial numbers 0R833820 and higher. Please use our Mercury Serial Number Guide to verify your engine's serial number before ordering.

Q: What are the signs of a failing water pump?

A: Common signs include a weak or non-existent water stream from the "tell-tale" outlet, engine overheating alarms, or a melted/deformed pump housing upon inspection.

Q: How often should the water pump impeller be replaced?

A: For preventative maintenance, it is recommended to inspect the water pump impeller annually and replace it every 1-2 years or every 100-200 hours of use, depending on operating conditions (e.g., saltwater vs. freshwater).

Q: OEM vs. Aftermarket?

A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?

A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?

A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

  • Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
  • This product is an aftermarket replacement part and is not an OEM component.
  • Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

  • Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
  • Fast Global Shipping: Free delivery worldwide in 5–15 days.
  • Direct from Manufacturer: Competitive pricing without compromising quality.
Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. Standard Shipping : 3-10 business days
  • If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
  • Please click here for more details>>> Return & Exchange Policy
SKU: 48210689028

Discover Niche Categories That Outsell

Top-Converting Item to Boost Your Average Order

4.9 ★★★★★
Based on 5 reviews
Sort
Highest Rating
Newest First
Oldest First
Product Reviews
E
Verified Purchase
Erik
West Palm Beach, US
★★★★★ 5
Sleeping on a soft cool cloud..
Color: White, Size: King
This pillow is nice and soft it holds the coldness for a long time and I am a big man.. As far as value I think it is worth it for the quality that goes into making it..
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on February 10, 2026
J
Verified Purchase
Jesse
Fort Morgan, US
★★★★★ 4
Nice Pillow
Color: White, Size: King
I waited a few weeks before writing this review. It’s very difficult to find Info on this pillow but here’s my take on it. Height: It’s a nice height on the pillow. It has a 2” gusset which upon my research is a way to keep the inside foam and down at least 2” high. Types of sleeping: I find this pillow to be comfortable in all sleep positions. I do find that because it’s not full foam that you don’t get that full compression feeling so back sleep is not as comfortable to me as other pillows I’ve used but still very comfortable Back: Has enough height that my neck is supported. It’s not full foam so you will have to adjust your head position so it fits perfectly into the curve of the pillow for best support. Side: Thick enough that the compatibility with my mattress sink allows my body to be comfortably aligned. I have a medium hybrid tempurpedic luxe breeze. Stomach: Just barely thick enough to be comfortable. I sleep somewhat weird and like my arm to go under the pillow. This gives me the correct height for stomach sleeping if I put my head on the bottom part of the pillow. This also allows me to breathe lol. Cooling This pillow has awesome cooling. Even when I wake up the pillow is still ice cold. Never had this feeling before and I’m a hot sleeper so i really like this. Granted I do set my house temperature to like 73 to sleep. The sensor is right next to my bed so it’s a true 73. Material This has foam outer layers and a fiber fill. It really does feel unique and it’s comfy. It’s a decently heavy pillow too in king so that gives confidence there is good quality foam and materials in it. One thing to know, the cover is “slippery” and it took some getting used to, even though I use a pillow case I can feel it slides in the case more than other pillows. I think it’s because the cover is very thing to promote airflow and heat transfer. I wish it was adjustable for the price. Price I like the pillow, and got mine on sale. But I do think it’s a bit overpriced for what it is. Evidently the sale price I got wasn’t a good price and it’s gone as much as 20% off. Oh well.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on August 18, 2023
M
Verified Purchase
Matthew
Dallas, US
★★★★★ 3
Great Cooling, But Lacking Support
Color: White, Size: Standard
I have to agree with some of the other reviews—this pillow just doesn't offer enough support. It initially feels plush and inviting, but after a minute or so, your head sinks too far and ends up pressing against the underlying latex, which has a rubbery, somewhat uncomfortable feel. It might be an excellent fit for those with smaller frames, but for me, it fell short in terms of proper neck and head support. On the plus side, the cooling aspect is impressive. It's cool to the touch and noticeably more breathable than many pillows I've tried. I've seen some complaints about it not staying cool all night, but honestly, no pillow really does. Casper's claim of "12 hours of cooling" seems like marketing optimism—your body heat will eventually warm up any pillow, no matter how well-designed. That’s just basic thermodynamics. All in all, it's a well-made pillow with excellent cooling performance. If you have a smaller frame, this could be a great choice. Unfortunately, it just didn’t work for my needs.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on June 7, 2025
B
Verified Purchase
BP
Whiting, US
★★★★★ 1
Is this a joke?
Color: White, Size: King
I don't usually write reviews, but I have to for this pillow. The pillow measures 16" x 32", not 18" x 34" as stated in the description. That's not really a big deal, but they should have the correct size in the description. The problem with this pillow is the total lack of support. My head falls through this pillow within a half hour of laying my head on it. This causes me neck pain and I have to switch to my old pillow in the middle of the night. I'm a bigger dude that's 6'3" and I only sleep on my side. I thought this pillow would be great based on the other reviews that stated it works for side sleepers. I would describe this pillow as a greatly overpriced marshmallow. The pillow does have some decent cooling properties, but they don't last all night as described. This pillow would probably work great for someone who sleeps on their stomach. I wouldn't recommend this pillow to a bigger dude that's a side sleeper. Note: I did find a great Casper pillow that works for me. I bought the Casper Sleep Essential Cooling Foam pillow on Amazon. It's the one that's all foam with a phase change layer to help with cooling. The pillow has great support and it doesn't cause me any neck pain. The best part is the price, it cost less than half the price of the Hybrid Snow Pillow. I hope this review helps someone.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on July 28, 2024
K
Verified Purchase
K. Farnsworth
Charlottesville, US
★★★★★ 5
A Near Perfect Pillow
Color: White, Size: King
I was hesitant to order this pillow because it was so expensive. I was looking for a cooling pillow and after a previously purchased pillow lost it's "cool" after a few nights of sleeping on it, I was concerned that this Casper pillow would do the same. The pillow is so comfortable. My only complaint is that it does not seem to hold the coolness all night. I find I need to flip the pillow over part way through the night. But, when I flip the pillow, it is perfectly cool. The pillow is supportive without being too firm. I love this pillow!
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on June 19, 2024

recommand products

Strawberry 2pc skort set
25.99
Banana Tree 180cm
194.50
Berry Blast Delta-8 THC 3500MG Gummies
24.99
Hyundai Genuine (Mobis) Part No.: 2103004001 Part Name BEARING PAIR SET-CRK/SHF CTR
253.00
REEFE RSFB250 Solar
150.00