Choosing a Garmin Force Kraken shaft starts with one measurement: the vertical distance from the trolling motor mounting surface at the bow to the waterline while the boat is floating in calm water. Boat length alone cannot tell you the right shaft length. A high bow or frequent chop can call for a longer model.
Measure your bow before choosing a shaft
- Float the boat in calm water with its usual gear aboard.
- Measure vertically from the surface where the Kraken mount will sit at the bow down to the waterline. Record that distance in inches.
- If you regularly fish in sizable waves, add 8 inches to the measurement before using the table. If your result fits two ranges, Garmin says to choose the longer shaft.
These are Garmin's Force Kraken recommendations. The ranges overlap by design; apply the longer-shaft rule where they do.
| Bow-to-waterline distance | Recommended Kraken shaft | Shop Rough Seas Marine |
|---|---|---|
| 0–19 in. | 48 in. | White 48 in. · Black 48 in. |
| 15–34 in. | 63 in. | White 63 in. · Black 63 in. |
| 26–46 in. | 75 in. | White 75 in. · Black 75 in. |
| 38–61 in. | 90 in. | White 90 in. · Black 90 in. |
| 53–81 in. | 110 in. | White 110 in. · Black 110 in. |
Example: If your calm-water bow measurement is 30 inches, both 63 and 75 inches appear in the table, so Garmin's overlap rule points to the 75-inch Kraken. If you frequently fish in sizable waves, add 8 inches first: 30 + 8 = 38 inches. That falls in the 75 and 90 inch ranges, so the rule points to the 90-inch model.
Why the extra shaft length matters
When the bow rises and falls, a short shaft can let the propeller get too close to the surface, reducing performance. A longer shaft gives you more depth adjustment for those conditions. The Kraken has an adjustable depth collar; after installation, deploy the motor and check its depth as Garmin directs. Shaft length is measured by Garmin from the bottom of the shaft cap to the top of the prop drive, so it is not the same as your bow-to-waterline measurement.
Check the installation and sonar package
Before ordering, check that the bow has room for the mount to deploy and stow, that the deck can support the installation, and that you can access the underside for mounting hardware. Garmin's installation instructions call for a 24 or 36 V DC battery bank able to supply 60 A continuously and a 60 A continuous-rated circuit breaker. Review the Garmin installation instructions for your setup.
Also compare the exact product configuration, not only the shaft length. Some of the black Kraken listings above include a built-in GT56UHD transducer, while the linked white models do not list that transducer. Confirm the exact part number, sonar plan, and mounting accessories on the product page before checkout.
Need a second opinion on your boat?
Send Rough Seas Marine your boat make and model, bow-to-waterline measurement, typical water conditions, and preferred sonar setup. We can help narrow down the Kraken length and product configuration before you order. Contact Rough Seas Marine or browse the models linked in the table.
Source: Garmin's Force trolling motor shaft length guidance. Verify the latest manufacturer instructions and the fit of your specific boat before installation.
