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I've got a 2004 Yamaha F50 that is struggling to reach the top RPM and top speed. I just recently cleaned out the carburetors and the motor was running beautifully, hitting 5500-5700 RPM with a light load, and sounded good at idle. I also balanced the carbs at the same time, but it was with a cheap balancer and it might not have been done correctly. Spark plugs are about a year old and need to be checked.
I did run into a sandbar a few weeks ago, took some waves over the stern, and had to clear some sand out of the motor's pee stream with a piece of weedwhacker wire. But this week out scooting around the motor ran fine for about two hours at 2000-3000 RPM. It sounded good and had a healthy idle. Then I just wanted to run it at wide open for a bit to burn off any water and carbon. I took it out and it went to 4500 and felt a little wavery and unsteady and I couldn't get it to go above that. I didn't experiment too much because I wanted to check oil and everything before running it more. Before I cleaned the carbs the motor also wouldn't get above 4500, but it was a clear fuel shortage problem with a block in the jets, in that situation there was a lot of vibration/choking around 2500RPM that didn't happen this time. It was super steady all the way up to 4500RPM but wouldn't go above that.
I'm curious what all I should check. It could be from the sandbar run in, maybe could be from improper balance between carbs and one spark plug getting all gunked up? Maybe I damaged the throttle linkage and it just isn't going all the way forward? Maybe a blockage in the fuel line preventing it from pulling enough juice? I also noticed that the oil has been getting steadily higher on the dipstick since I changed is ~4 months ago (I suspect the fuel pump is adding gasoline to the oil) but it is just barely above the hash marks and I wouldn't think that would cause this but maybe?
Any advice on what to dig into first as I try to diagnose this?
I did run into a sandbar a few weeks ago, took some waves over the stern, and had to clear some sand out of the motor's pee stream with a piece of weedwhacker wire. But this week out scooting around the motor ran fine for about two hours at 2000-3000 RPM. It sounded good and had a healthy idle. Then I just wanted to run it at wide open for a bit to burn off any water and carbon. I took it out and it went to 4500 and felt a little wavery and unsteady and I couldn't get it to go above that. I didn't experiment too much because I wanted to check oil and everything before running it more. Before I cleaned the carbs the motor also wouldn't get above 4500, but it was a clear fuel shortage problem with a block in the jets, in that situation there was a lot of vibration/choking around 2500RPM that didn't happen this time. It was super steady all the way up to 4500RPM but wouldn't go above that.
I'm curious what all I should check. It could be from the sandbar run in, maybe could be from improper balance between carbs and one spark plug getting all gunked up? Maybe I damaged the throttle linkage and it just isn't going all the way forward? Maybe a blockage in the fuel line preventing it from pulling enough juice? I also noticed that the oil has been getting steadily higher on the dipstick since I changed is ~4 months ago (I suspect the fuel pump is adding gasoline to the oil) but it is just barely above the hash marks and I wouldn't think that would cause this but maybe?
Any advice on what to dig into first as I try to diagnose this?