Check Ball Kit – Fits MerCruiser R/MR/Alpha One Drives (1983–1990) (Replaces 30-98475T1)
Check Ball Kit – Fits MerCruiser R/MR/Alpha One Drives (1983–1990) (Replaces 30-98475T1) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Product Details
This is a direct replacement Check Ball Kit – Fits MerCruiser R/MR/Alpha One Drives (1983–1990) (Replaces 30-98475T1). It is engineered for use with MerCruiser R, MR, and Alpha One sterndrive applications manufactured between 1983 and 1990.
This kit serves as a direct interchange for Mercury/MerCruiser part numbers 30-98475T1 and 98475T1, ensuring proper fit and function.
- Designed for direct replacement of the original components.
- Specifically made for R/MR/Alpha One sterndrive units.
- Includes all necessary check balls for a complete service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury/MerCruiser | 30-98475T1 |
| Mercury/MerCruiser | 98475T1 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For MerCruiser applications, this kit is specifically designed for the sterndrive units listed, not specific engine horsepower ratings.
| Brand | Model | Years | OEM Part No. |
|---|---|---|---|
| MerCruiser | R Drive | 1983–1990 | 30-98475T1 |
| MerCruiser | MR Drive | 1983–1990 | 30-98475T1 |
| MerCruiser | Alpha One Drive | 1983–1990 | 30-98475T1 |
Technical Specs
- Product Type
- Check Ball Kit
- Installation
- Direct replacement
- Application
- For R/MR/Alpha One sterndrive units
- Dimensions
- 14.0" × 10.0" × 2.0" (355.6 mm × 254 mm × 50.8 mm)
- Weight
- 0.036 kg (0.08 lb)
- Warranty
- 1 year factory warranty
What’s in the Box
- Check Ball Kit (Replaces 30-98475T1)
Installation Notes
- Ensure the sterndrive is safely secured and disconnect the battery before beginning work.
- Access the upper gearcase housing where the check balls are located. This may require partial disassembly of the drive.
- Carefully remove the old check balls and any associated seats or springs, paying close attention to their order and orientation.
- Thoroughly clean the cavities and mating surfaces to remove any debris or sealant residue.
- Install the new check balls from the kit in the correct sequence as noted during disassembly.
- Reassemble all components using new gaskets and O-rings where required. Torque all fasteners to the manufacturer's specified values.
- Once assembled, reconnect the battery and test the shifting and drive operation in a controlled environment before returning to full service.
Troubleshooting & FAQ
How do I know if my sterndrive's check balls need replacing?
Common symptoms of failed or worn check balls include difficulty shifting, clunking noises during gear engagement, or a failure to hold in forward or reverse gear. A visual inspection during routine service may also reveal worn or damaged components.
Will this kit fit an Alpha One Gen II drive?
No, this kit is specifically for the earlier R, MR, and original Alpha One drives manufactured from 1983 to 1990. Alpha One Gen II drives use different internal components.
What is the function of a check ball in a MerCruiser drive?
Check balls are small, typically rubber or plastic balls that act as one-way valves within the hydraulic and oil passages of the sterndrive's shift mechanism. They control fluid flow to engage and disengage the forward and reverse gears.
Can I complete this installation myself?
While the process is straightforward for those with mechanical experience, it involves critical drive components. We recommend professional installation to ensure correct assembly, sealing, and reliable performance.
Is this an OEM part or an aftermarket equivalent?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials. Our parts are manufactured in an ISO 9002 facility and are batch-inspected for quality and consistency.
How fast is shipping and what does it cost?
We ship worldwide quickly—typical transit time is 5–15 days. Standard shipping is free to most locations, with expedited options available at checkout where applicable.
What is the warranty and return policy on this part?
This product is covered by a 1-year warranty against manufacturing defects under normal use. If you encounter any issues, please contact our support team with your order details. Returns are accepted within our standard window for unused items in their original condition. See our policy page or reach out for instructions.
Safety & Important Info
- Verify images and specifications against your original part before purchase. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement part, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world conditions.
- Fast Global Fulfillment — We offer free standard delivery to most regions, with typical transit times of 5–15 days.
- Manufacturer-Direct Value — Our direct-sourcing model ensures fair pricing without compromising on materials or quality control.
Payment & Security
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