rpm going up and down 2001 saltwater II

[new england]

Hello, We just bought a used 21 foot power boat. 1990. With a 2001 yamaha 250 hp saltwater II series engine-outboard. Engine runs fine. But at various rpms it either surges or powers down. For instance, bringing her up to 2,500...all on its own it surges to 3,300. Or reverse. She seems to hold steady at 3,000.

This is our first power boat. Any suggestions would be appreciated.

I just edited the numbers. Sorry, I was in the wrong range.

[99yam40]

the motor should not run above 5500

[new england]

Thank you. I just corrected those numbers. Still learning.

[jb123]

Clean /test 02 sensor
Monitor rail pressure

[bajakeith]

surge

start with all three lift pumps and new (good) fuel line and primer bulb assempy (not tempo,attwood,moeller) and try again...the VST filter is very prone to clogging on that Great motor...BTW...2 strokers ROCK !! make sure the primer bulb is close to motor with the arrow poining upwards as towards the sky and not laying on its side or any other direction !! does make a diff !!

[new england]

Thank you. We had a mechanic look at it and he said the engine was fine and that we needed to learn how to trim the engine at certain speeds. That seemed to help quite a bit.

But I will copy all of these suggestions.