Answer
Sep 03, 2025 - 06:29 PM
To figure out the age and model of your Yamaha 8HP outboard, check the ID plate or sticker on the mounting bracket (usually on the port side). You’ll see a model code like 8CMH, and a longer number that includes the year code. Sometimes Yamaha sneaks the year into the serial format, but it’s not always straightforward.
Feel free to send us the model number and serial, and we'll gladly help decode it for you (and even find you the best manual for your needs).
Now for the running issue — if it cranks and fires up but only runs for 3 to 5 seconds, couple things come to mind:
- Fuel issue – try pumping the primer bulb while it’s running. If it stays running as you pump, your fuel pump or lines might be the problem.
- Dirty carb – especially if it sat for a while. Float might be stuck or jets partially clogged.
- Kill switch or safety lanyard – sounds basic, but if that’s acting up it can cut spark after startup.
- Fuel vent closed – make sure the fuel tank vent is open so it’s not starving for air.
If it starts easy but dies out, it’s usually fuel-related 9 times out of 10. The service manual often covers the troubleshooting chart for such engine issues, so you may want to check it out for more details.
