Repower an old 15’ Dauntless

[DavidK]

We inherited an older 15’ Boston Whaler Dauntless with a 75 hp Mariner motor. The boat’s in great shape but the motor is frustratingly unreliable and I’d like to replace it with a new one. My priorities are 1) reliability and 2) quietness. I’m leaning towards a Honda, but I’m looking for fellow owner recommendations for both brand, model and size (hp). Thanks!

[CaptBrett]

Hello Capt,  

Nice rig to inherit. I would highly recommend a Yamaha over a Honda any day.  However, I have no bad things to say about Honda.  My views are: 1. I just spent the last year completely restoring a 1983 15' Super Sport.  These old 15's were all rated for a 70 hp.  I think Yamaha makes the best 70 4-stroke you can buy.  

When comparing Honda Marine and Yamaha Marine 70 horsepower (HP) outboard motors, both brands offer strong performance, reliability, and advanced technology. However, there are several key differences in their features, performance characteristics, and overall design. Here's a breakdown of each:

Honda Marine 70 HP Outboard

• Model: BF70
• Engine Type: 4-stroke
• Displacement: 998 cc (cubic centimeters)
• Cylinders: 4 cylinders, inline
• Fuel System: Programmed Fuel Injection (PGM-FI)
• Cooling System: Water-cooled
• Weight: Approximately 206 lbs (93.5 kg) for the standard model
• Power-to-Weight Ratio: Honda is known for its smooth and quiet engines, and the BF70's power-to-weight ratio makes it a great option for smaller boats that need efficient power without adding excessive weight.

Key Features:

• Quiet Operation: Honda’s four-stroke technology is known for providing smoother, quieter operation compared to two-stroke engines.
• Fuel Efficiency: Honda’s PGM-FI system enhances fuel efficiency, helping to save on fuel costs over time.
• Durability: Honda engines are renowned for their longevity and reliability, which is often attributed to their advanced engineering and durable construction.
• Low Emissions: The Honda BF70 complies with stringent EPA and CARB (California Air Resources Board) standards, which makes it one of the more environmentally friendly options.
• Variable Valve Timing (VVT): Honda uses VVT to optimize power output, providing a balance of performance and fuel economy throughout the RPM range.

Yamaha Marine 70 HP Outboard

• Model: F70
• Engine Type: 4-stroke
• Displacement: 996 cc
• Cylinders: 4 cylinders, inline
• Fuel System: EFI (Electronic Fuel Injection)
• Cooling System: Water-cooled
• Weight: Approximately 249 lbs (113.9 kg) for the standard model
• Power-to-Weight Ratio: Yamaha's F70 is a bit heavier than the Honda BF70, but it’s still known for being relatively light in comparison to other engines in the same power class.

Key Features:

• Performance and Power: Yamaha’s F70 is designed for excellent mid-range performance and strong low-end torque, making it ideal for a wide variety of applications, from fishing to recreational boating.
• Reliability: Yamaha has a reputation for building long-lasting, reliable engines, and the F70 continues that tradition with tough components and quality manufacturing.
• Fuel Efficiency: Yamaha's EFI system provides excellent fuel efficiency and smoother performance at all RPM ranges, similar to Honda's PGM-FI technology.
• Electronic Controls: Yamaha offers advanced electronic controls that allow for smoother shifting, better throttle response, and more precise control, particularly at low speeds.
• Quietness and Vibration: Like Honda, Yamaha’s four-stroke engines are quieter than two-strokes, and the F70 features advanced engineering to minimize vibration, ensuring a comfortable experience on the water.

Comparison Summary

Feature	Honda BF70	Yamaha F70
Engine Type	4-stroke	4-stroke
Displacement	998 cc	996 cc
Power Output	70 HP	70 HP
Weight	~206 lbs (93.5 kg)	~249 lbs (113.9 kg)
Fuel System	Programmed Fuel Injection (PGM-FI)	Electronic Fuel Injection (EFI)
Cooling System	Water-cooled	Water-cooled
Noise Level	Very quiet, smooth operation	Quiet, but slightly more noise than Honda
Fuel Efficiency	Very fuel-efficient, low emissions	Very fuel-efficient, low emissions
Reliability	High reliability, long lifespan	High reliability, long lifespan
Electronic Control	Standard controls, minimal electronics	Advanced electronic controls, smooth shifting
Price Range	Generally priced slightly lower	Slightly higher due to advanced features

Which One to Choose?

• Honda BF70: If you prioritize quiet operation, fuel efficiency, and a slightly lighter engine for your boat, the Honda BF70 may be the better option. It’s known for smooth, quiet operation and is a great choice for environmentally-conscious buyers due to its low emissions.
• Yamaha F70: If you’re looking for a slightly more powerful low-end torque and prefer advanced electronic controls (like smoother shifting and better throttle response), the Yamaha F70 could be the better fit. It’s also slightly heavier, but it offers excellent reliability and strong overall performance.

Ultimately, both motors are highly reliable, efficient, and suitable for various boating activities. Your decision may come down to which brand you have a preference for, the weight considerations for your boat, and the specific features you find most important.