Short or Long Shaft Outboards: How to Choose For Boston Whalers

Choosing Between a Short or Long Shaft Outboard Motor

When selecting an outboard motor for your boat, one of the most important decisions is whether you need a short shaft or long shaft model. The shaft length impacts how the engine mounts to the transom and propeller depth in the water. For Boston Whaler boats with 20" transoms, short shaft Mercury Marine outboards around 15 inches are typically recommended.

What is a Short Shaft Outboard?

A short shaft outboard motor has a shaft length less than 20 inches. Short shaft outboards range from 15 to 20 inches usually. They work well on small boats and little boats with lower transom heights and lighter loads.

The shorter shaft positions the propeller higher out of the water, providing adequate depth while allowing the engine to mount closer to the transom. This improves weight distribution and stability on smaller hulls.

When to Choose a Short Shaft

• Inflatables and ribs less than 15 feet
• Light-duty aluminum boats under 16 feet
• Older Boston Whaler models around 13 to 16 feet
• Fishing skiffs and microskiffs 12 to 14 feet

The Boston Whaler Montauk and other models around 15 to 17 feet work well with a short shaft Mercury Marine or other 15 inch outboard if they have a 20 inch transom height.

Considerations with Short Shaft Outboards

The main downside of short shaft outboard engines is less flexibility if you decide to repower a different boat later. They also may not provide ideal propeller depth and engine mounting on larger transom heights.

When to Use a Long Shaft Motor

Conversely, long shaft outboards have a shaft length greater than 20 inches, usually ranging from 20 to 25 inches. They allow more adjustable mounting height and propeller depth for larger boats.

• Center console fishing boats 18 feet and up
• Pontoons 20 feet and longer
• Heavier bay boats and dual console models
• Boston Whaler Montauk 17 and larger

Benefits of Long Shaft Outboards

Long shaft Mercury outboards allow you to fine tune the engine height and prop depth for optimum performance. This added adjustment range benefits boats with 24+ inch transoms and heavier aft loads.

You also have more flexibility if remounting the outboard on a different boat later. The long shaft motor can adapt to more transom heights.

Downsides of Long Shaft Motors

On smaller fishing boats and hulls under 18 feet, a long shaft motor might hang too low, causing issues with ventilation and prop clearance. Always match your boat's needs and manufacturers requirements.

FAQ

Can I mount a short shaft motor on a 25" transom?

This is generally not recommended, as the short shaft will limit adjustment range and likely not achieve proper mounting height or propeller depth.

What size Boston Whaler needs a long shaft outboard?

Boston Whaler recommends transitioning to a long shaft outboard around 17 feet and above. But also consider your actual transom height and other factors.

Key Takeaways on Short vs Long Shaft Motors

• Always match shaft length to transom height and boat size
• Check manufacturer mounting recommendations
• Short shaft better for small fishing boats under 16 feet
• Long shaft allows more mounting adjustment on larger transoms

Choosing the right shaft length is critical for optimum performance and handling. Consider your actual transom height, boat length and weight capacity when deciding between short vs long. #mercurymarine #bostonwhaler #shortshaft #outboards #outboardengines #willitwork #longshaft #smallboat #littleboat

FAQs

What is the best short shaft outboard motor for a 14 ft boat?

For a lightweight 14 foot skiff or jon boat, the Mercury 15 HP and 20 HP portable outboards work very well. They are easy to mount and provide ample power while keeping the boat balanced.

What shaft length does Mercury recommend for a Boston Whaler Dauntless 17?

Mercury Marine recommends a 20 inch long shaft motor for the Boston Whaler 17 Dauntless model. This allows proper mounting height and clearance.

Can I use a long shaft motor on a short transom?

You can, but it will hang lower and may cause issues with ventilation and propeller clearance in the water. You also lose some ability to fine tune the height.

What is the lightest short shaft outboard under 20 HP?

The lightest short shaft outboard under 20 HP is the Mercury 15 HP EFI 4-stroke at just 105 pounds. This portable engine works very well for small fishing boats and inflatables.