Yamaha F70A v. F70B

[msteinkampf]

I’m about to re-power my Montauk 17 with a Yamaha F70. I understand Yamaha has just come out with an F70B model.

Q1: what differs on a Yamaha F70B from a Yamaha F70A?

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[jimh]

This reply to your question was generated by ChatGPT:

The Yamaha F70B is an updated version of the Yamaha F70A, and while they are very similar in many respects (both are 70 hp, inline 4-cylinder, 1.0L outboards), there are a few key differences that set them apart:

Key Differences: F70B vs. F70A

1. Updated Cowling Design

F70B has a redesigned cowling for improved aesthetics and better airflow.
It's a bit sleeker and modern-looking compared to the F70A.

2. Newer ECM & Software Updates

The F70B has updated engine control software and sometimes newer components inside the ECM (Engine Control Module), which can slightly improve efficiency, diagnostics, and compatibility with newer gauges and controls.

3. Improved Corrosion Resistance

Yamaha made minor refinements in corrosion protection in the F70B, especially in the paint and coating processes.

4. Drive-by-Wire Compatibility? (Region-specific)

In some markets, Yamaha has introduced rigging upgrades with the F70B. For instance, the F70B might support more modern controls (like digital gauges or compatibility with Helm Master EX), though it’s still a mechanically-controlled engine. This isn’t always listed officially but depends on the region and dealer offerings.

5. Weight and Dimensions

Very minor differences, if any — both models weigh around 253 lbs (lightest 70 hp 4-stroke in its class), but the F70B may have a few internal refinements or slight tweaks in mounting hardware.


What Stays the Same


• 1.0L displacement
• Inline 4-cylinder
• EFI (Electronic Fuel Injection)
• Long (20") and Extra Long (25") shaft options
• Same propeller compatibility and performance characteristics

If you're choosing between the two, the F70B is just a slightly refreshed and refined version of the F70A. Think of it like a "facelift" in the automotive world — same core, but with a bit of polishing.

[msteinkampf]

[The ChatGPT answer is] not a bad assessment. The parts catalogs for the F70A and F70B are now available online at:

https://yamahaoutboards.com/
Click on Owner Center and then Outboard Parts to get to the parts catalogs.

Part numbers differ for the cowling, ECU, float chamber assembly, stator, and wire harness; otherwise, they are about the same. The alternator output has been increased to 17 Amperes versus 15 Amperes for the F70A. My Yamaha dealer told me that all the new models coming out have increased alternator outputs to power the gadgets boaters are installing.

The F70B is available in brown color.

New Yamaha F70B engine color: brown.

Mid-70-OverviewLifestyle03_1.jpg (16.03 KiB) Viewed 220 times

[Moderator's note: added photo-image showing new engine color option.]