2007 Mercruiser 4.3 Changes Speed

[thunder219]

I took the boat out yesterday, I ran across the lake and everything was fine but on the way back I noticed the boat would speed up and slow down about 700-900 rpm without me touching the throttle. I changed the water separator out when I got home but I have no clue where to start looking on this issue. The actual speed changed also not just the rpms. The throttle has resistance to it also so I don't think that's the issue. Thank you for any help

 

[R055]

Hard to say but sounds like fuel, did you check the old fuel filter by dumping the contents into a clear cup/bottle?

 

[thunder219]

I did. It was late last night so I haven't checked it since I poured it in. I had an extra fuel filter separator so decided to start simple. I will reply after I get home to what the gas looks like

 

[thunder219]

I checked it when I got home and there was no water in it unfortunately

 

[alldodge]

Is this a carb or EFI motor, a serial number could help?

 

[thunder219]

It is a carb. I will look for a serial number on it when I get home. It ran well it just has never done that in the 9 years I've had it.

 

[alldodge]

Being a carb, I would also be thinking fuel issue and the carb may need a cleaning. Could also be fuel pump or line restriction.