Help with rough acceleration on Volvo 3.0

Joined
May 28, 2009
Messages
13
Took the boat out today, and it ran fine for the first half of the day. On our way home, I noticed a faint popping/chuffing sound when running on plane. I stopped and the boat was idling roughly and almost died a time or two. When revving the engine with the boat in neutral, the sound was worse while quickly opening the throttle, however once the engine leveled off at a given RPM it seemed to run fine. I opened the engine lid and the noise seemed to be coming from the carb/flame arrestor. We brought the boat on in and symptoms continued.

I got home, pulled the plugs, and they all look fine. I then cleaned them anyway for good measure. I put the boat on the hose and took the flame arrestor off, and was still experiencing the same symptoms. I sprayed a good bit of carb cleaner through it with no improvement.

Fuel is fresh.

I know it is difficult to describe symptoms like this, so I took a video so you can see and hear what I am dealing with. Note that the boat wants to die if I return it all the way to a 900 rpm idle. Also there is no "chuffing" sound when advancing the throttle slowly or when at a steady high RPM, but only when advancing the throttle quickly (It was doing it constantly, however, at steady higher RPMs while on the water under load. Also there was a slight loss of power). See: http://www.youtube.com/watch?v=Ao1yWL6wcig

I am thinking either the there may be a problem with the timing but more likely something in the carb is not right. Any ideas?
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Help with rough acceleration on Volvo 3.0

Defective accelerator pump, water in carb, carb out of adjustment. Hard to say for certain. But it should idle down to 650 rpm with no problem.
Has it had a full tuneup lately? How about a compression check?
You might want to install a water seperating fuel filter. The E10 fuels can play havoc on your carb without one.
 
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