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The short answer
A common rule of thumb is about 2 lb of thrust for every 100 lb of fully loaded boat weight, then add more for wind, current and heavier water. Most bass boats land in the 80–115 lb range on a 24V or 36V system, which is why motors like the Minn Kota Ultrex QUEST 90/115 and Lowrance Ghost are so popular. For shaft length, measure from the mount to the waterline and add enough that the prop stays 12 inches or more below the surface. If you fish salt water, choose a saltwater model like the Minn Kota Riptide Terrova QUEST.
Our top picks
- Best for bass boats: Minn Kota Ultrex QUEST 90/115 — 90 lb on 24V or 115 lb on 36V, brand-rated. Check price on Amazon
- Best for heavier freshwater boats: Lowrance Ghost 47″ — Lowrance rates it at 97/120 lb thrust. Check price on Amazon
- Best for salt water: Minn Kota Riptide Terrova QUEST 90/115 — Brushless and built for coastal boats. Check price on Amazon
Thrust by boat weight at a glance
| Loaded boat weight | Suggested thrust | Typical voltage | Example motor | Best for | Amazon |
|---|---|---|---|---|---|
| Up to about 2,500 lb | About 55 lb or more | 12V | Minn Kota Edge 55 (cable-steer bow mount) | Jon boats, small aluminum boats | Check price |
| About 2,500–4,000 lb | About 80 lb or more | 24V | Minn Kota Riptide Terrova 80 | Mid-size fishing boats | Check price |
| About 3,500–5,000 lb | About 90–115 lb | 24V or 36V | Minn Kota Ultrex QUEST 90/115 | Bass boats | Check price |
| Heavier freshwater boats | About 100–120 lb | 36V | Lowrance Ghost | Big bass and multi-species boats | Check price |
| Bay boats and center consoles | About 90–115 lb | 24V or 36V | Minn Kota Riptide Terrova QUEST | Coastal fishing | Check price |
How we built this guide
We compared manufacturer sizing guidance, specifications, owner reviews and published reviews from established boating and fishing outlets. Manufacturers publish their own thrust charts, and they differ slightly, so treat the numbers here as a starting point and check the brand’s recommendation for your exact boat.
Step 1: Work out your loaded boat weight
Start with your boat’s dry weight from the manufacturer, then add the weight of your outboard, fuel, batteries, gear, livewell water and passengers. Fully loaded weight is often much higher than dry weight, and it’s the number that matters for thrust. When in doubt, round up.
Step 2: Choose thrust
Use roughly 2 lb of thrust per 100 lb of loaded weight as a baseline. Then size up if you fish in wind, current or tides, if your boat is tall-sided and catches wind, or if you plan to use GPS anchoring a lot. Anchoring in wind is one of the hardest jobs a trolling motor does, and an underpowered motor will drain batteries trying to keep up.
Many premium motors, including the Minn Kota QUEST family, are rated for different thrust at different voltages. The Ultrex QUEST 90/115, for example, is rated at 90 lb on 24V and 115 lb on 36V.
Step 3: Choose voltage
Voltage determines how many batteries you need and how much thrust a motor can produce.
- 12V (one battery). Suits small boats and lighter thrust, typically up to about 55 lb.
- 24V (two batteries). Common for mid-size boats and motors around 70–90 lb.
- 36V (three batteries). Standard on most bass boats and heavier boats, with thrust above 100 lb.
Higher voltage generally means more thrust and better efficiency, but more battery weight and cost. Lithium batteries reduce weight significantly.
Step 4: Choose shaft length
Shaft length keeps the prop in the water. Too short, and the prop comes out of the water in waves. Too long, and it drags in shallow water and is awkward to stow. Measure from the top of your mounting surface to the waterline, then add enough length that the motor’s lower unit sits at least 12 inches below the surface. Add more if you fish rough water.
Most bass boats use 45–60 inch shafts. Taller bay boats and center consoles often need 72–87 inches. Our saltwater trolling motor picks include longer shafts for those boats.
Step 5: Decide on features
Once you know the size, choose features. GPS anchoring (Spot-Lock and similar) is the most valuable upgrade for most anglers. Built-in sonar transducers save mounting a separate transducer. Brushless motors run longer per charge. See our GPS trolling motor picks for the best options.
Bow mount or transom mount?
Bow-mount motors pull the boat from the front, which gives you much better control when fishing a shoreline or holding on a spot. They’re the standard on bass boats, bay boats and most dedicated fishing boats, and they’re the only type that offers advanced GPS anchoring in most lineups. Transom-mount motors push from the back, cost less and suit small jon boats, canoes and boats used mainly for slow trolling. If you fish seriously from the front deck, a bow mount is worth it.
A sizing example
Say you run an 18-foot bass boat with a dry weight of about 1,300 lb. Add a 150 hp outboard, a full tank of fuel, three batteries, a livewell of water, tackle and two anglers, and the loaded weight can easily climb past 3,500 lb. At 2 lb of thrust per 100 lb, you’d want at least 70 lb of thrust. Add margin for wind and GPS anchoring, and an 80–115 lb motor on 24V or 36V is a comfortable fit. That’s why so many bass boats run motors like the Minn Kota Ultrex QUEST 90/115.
For shaft length on the same boat, measure from the bow deck to the waterline. If it’s about 20 inches, a 45–52 inch shaft keeps the prop well under the surface in normal chop. If you fish big, rough lakes, go longer.
Recommended motors by size
For most bass boats, the Minn Kota Ultrex QUEST 90/115 covers the most common sizing range with a brushless motor and Spot-Lock. For heavier freshwater boats, the Lowrance Ghost is rated for up to 120 lb on 36V. For Garmin-networked boats, the Garmin Force Kraken is a quiet, brushless alternative. For coastal boats, the Minn Kota Riptide Terrova QUEST brings brushless power to salt water.
Good to know: if you also plan to run live sonar on the trolling motor shaft, check mount compatibility. Our forward-facing sonar guide covers mounts.
Sizing checklist
- Use loaded weight. Include people, gear, fuel and batteries, not just the boat’s dry weight.
- Size up for wind and current. Extra thrust saves battery when anchoring in tough conditions.
- Match voltage to your battery space. Three batteries for 36V take room and add weight.
- Measure shaft length carefully. Keep the prop at least 12 inches under the surface.
- Freshwater or salt. Choose a saltwater model for coastal use.
- Check the brand’s chart. Manufacturers publish sizing guidance for their motors.
FAQ
How much thrust do I need for my boat?
A common rule of thumb is about 2 lb of thrust for every 100 lb of fully loaded boat weight, with more for wind, current or heavy GPS anchoring use.
Is 24V or 36V better for a trolling motor?
36V produces more thrust and is standard on most bass boats, while 24V suits lighter boats and needs one fewer battery. Choose based on boat weight and battery space.
What shaft length do I need for my trolling motor?
Measure from the mount to the waterline and add enough length so the motor sits at least 12 inches below the surface. Most bass boats use 45–60 inch shafts; taller boats need more.
Can a trolling motor be too powerful for my boat?
Not usually. Extra thrust gives you more control and efficiency at lower speeds. The main downsides are higher cost and the extra battery weight of higher-voltage systems.
Do I need a saltwater trolling motor for coastal fishing?
Yes. Saltwater models add sealing and corrosion protection. Using a freshwater motor in salt can shorten its life and may affect warranty coverage.