1991 Yamaha Waverunner Owners Manual 1991 Yamaha WaveRunner Problems!?

1991 Yamaha WaveRunner Problems!? - 1991 yamaha waverunner owners manual

I recently bought a 1991 Yamaha Waverunner 500cc. I have new NGK spark plugs in this letter and a box of sea moss and gases. I met this weekend and I have good start, but has no power at all low-end or high end. I opened the lake and is the top speed was probably 10 mph. I do not know what the problem is. Any help! plz!