by Mark Sanders
(Sequim,, WA)
I bought a boat with a 1998 Yamaha 15 HP, 4 Stroke engine, F15ELHX, which was not running well. Since purchase, I have gotten “most” issues worked out, but in order to run at full throttle and power, the engine needs the choke out about ¼ inch. I am asking for input on what I might look into to correct this issue. Since I started working on the engine, this is what has occurred:
1. Rebuilt the carburetor (no soak). Disassembled, cleaned low and high speed jets. Sprayed ports with carburetor cleaner.
2. Replaced Inline Fuel Screen.
3. Replaced Spark Plugs.
4. Discovered bad fuel in the tank supplied by the seller. Dumped tank and refilled. Added Stabil 360 Marine Additive.
5. Pulled Fuel Tank Dip Tube and Checked Screen. Screen was Clean.
6. Added Sea Foam to new fuel in fuel tank. Fuel was regular unleaded, E10.
7. Pulled carburetor and Cleaned Again (No Soak, though).
8. Replaced Fuel Pump.
All in all the engine is running well at low speed and OK at full throttle, but still needs the choke pulled out about ¼ inch.
Currently, I have a new fuel tank and a new Yamaha fuel line. I am looking for any additional suggestions. Thanks in advance for any suggestions on things that I may have missed.