Hi guys,

I've used this forum for years helping me diagnose problems and it's always been very helpful. Now I have encountered a more difficult problem which I why I'm posting today.

I have a 2004 Yamaha FX HO Cruiser, and haven't used it since November. Last weekend, I started it up for the first time since then and it started with no problems. I let it warm up for a few minutes and checked to make sure the pisser was working (it seemed to be working, at least intermittently when idling). After a few minutes, I tried to open it up full throttle. Immediately I could tell something was wrong, as it struggled to get past 23 MPH and wouldn't even get up on a plane. I proceeded to bring it back to the dock to think things over.

After a couple hours of it resting at the dock, I decided to try again. This time, after idling for a few minutes and then goosing it a few times, the overheat indicator started buzzing. Once again, I took it back to the dock to think things over. An hour later, after the block had cooled, I started her up again. This time, the overheat indicator started buzzing immediately. Just to make sure that I wasn't crazy, I read temps off the engine using an IR thermometer and didn't read anything over 140 F.

Having read that the overheat indicator will limit the ski to 3,000 RPM, I took the ski out on the water and found that I was able to get the ski up to ~6,000 RPM. On the dock, when flushing the ski, I can throttle it to ~9,000 RPM. If the overheat indicator is on, why am I able to get the ski to over 6,000 RPM?

Here are my thoughts and what I've tried so far: There may be two independent problems. I believe this may be the case because before the overheat buzzer ever sounded (meaning the RPMs shouldn't have been limited) I couldn't get the ski up to speed. I believe that one of the thermo switches or thermo sensor is bad, since every time I start the ski it sounds immediately, even when it's completely cold. As a side note, I have replaced the spark plugs to eliminate that as a problem, and non-ethanol gas (with seafoam) was used in November, so my inclination is not the gas, however I could be wrong.

I know it's a complicated issue, but I'd appreciate your guys' thoughts/opinions. Please tell me what you think my next steps should be. I'd love help solving this problem! Thank you.