2000 Volvo Penta 5.7L GL Lacks Top Speed

[Johnshan1]

I have a 2000 Larson with the volvo penta 5.7L engine, duo prop. I have always had a 40 mph top end until recently. The boat is running at 4000 RPMS at full throttle as always, but I am only getting a 30 mph top end speed. It sounds like its hesitating at full throttle as well. If I back it off a touch it will smooth out and I actually gain a mph or 2.

Is it safe to assume my carb is getting gummed up? I have run 85 hours this season on ethanol fuel. I cleaned the tank out and replaced the filter prior to this season and the addition of ethanol.

The boat runs great otherwise- should I pull the carb and clean/inspect?

Thanks for any input.

The bottom is clean by the way- spotless actually.

 

[Johnshan1]

Re: 2000 Volvo Penta 5.7L GL Lacks Top Speed

Also, I did verify that the throttle plate is opening all the way.

 

[BILL INGRAHAM]

Re: 2000 Volvo Penta 5.7L GL Lacks Top Speed

Is Your Io And Props Growth Free? A Few Barnacles And 90 Degree Air Slow Me From 4600 To 4200 Rpm.backing Off Throttle Will Temporarily Lean And Reduce Timing Slightly-possible Rich Condition At Wot? E 10 Can Challenge Components Even Though Certified.

 

[Johnshan1]

Re: 2000 Volvo Penta 5.7L GL Lacks Top Speed

The lower end and props are clean. It sure seems like theres something holding this back.

Can I simply remove the fuel bowl and look for crud without removing the carb?