J
Jeff Page
Guest
"I own a 90HP 2-stroke from th
"I own a 90HP 2-stroke from the late 90s with few hours and it has run perfectly until recently.
Initially, I believed it was bad fuel, or a fuel delivery problem, but after replacing the gas, fuel tank, connectors, line, filter and squeeze bulb, and then disassembling the carburetors, fuel filter and fuel pump and finding everything pristine, it must therefore be electrical.
Sometimes it runs perfectly. At other times, it acts like there is water in the fuel. Add throttle and it balks and chugs, then runs smoothly but tops out at exactly 4000 rpm (normal with this prop is 5500). Sometimes it surges, as it there is a switch flipping on and off that doubles the power output. This occurs faster than water going through the card could cause. When it is running poorly, the idle is very slightly rough.
It always starts easily.
There is a yellow wire connected to the CDI unit, that when disconnected, bypasses the computer so you can get back to port. If I disconnect it, the engine runs much worse than when it is running poorly, so I don't think there is a bad connection there.
I have disconnected every single connector. there is no water or corrosion in any of them and they are making good contact.
I own the official Yamaha service manual, but it's troubleshooting guide covers only basics.
Before I start randomly purchasing electrical parts, I would appreciate any ideas how to diagnose this."
"I own a 90HP 2-stroke from the late 90s with few hours and it has run perfectly until recently.
Initially, I believed it was bad fuel, or a fuel delivery problem, but after replacing the gas, fuel tank, connectors, line, filter and squeeze bulb, and then disassembling the carburetors, fuel filter and fuel pump and finding everything pristine, it must therefore be electrical.
Sometimes it runs perfectly. At other times, it acts like there is water in the fuel. Add throttle and it balks and chugs, then runs smoothly but tops out at exactly 4000 rpm (normal with this prop is 5500). Sometimes it surges, as it there is a switch flipping on and off that doubles the power output. This occurs faster than water going through the card could cause. When it is running poorly, the idle is very slightly rough.
It always starts easily.
There is a yellow wire connected to the CDI unit, that when disconnected, bypasses the computer so you can get back to port. If I disconnect it, the engine runs much worse than when it is running poorly, so I don't think there is a bad connection there.
I have disconnected every single connector. there is no water or corrosion in any of them and they are making good contact.
I own the official Yamaha service manual, but it's troubleshooting guide covers only basics.
Before I start randomly purchasing electrical parts, I would appreciate any ideas how to diagnose this."
