Serious engine stumble with 3.0L 2009 Volvo with Demon 2bbl Carb

[YahooMarine]

Hello. I have read many threads on this site about carb issues but they all seem to be with Holley carbs. My 2009 Chaparral has a Demon 2bbl carb.

It was great when new 2 years ago in the summer of 2009. In early 2010 Volvo recalled the engine for a potential carb problem involving loose screws. The dealer inspected the carb and declared my ok. However, ever since the engine is hard to start and this year stumbles badly and stalls if I throttle up hard at low rpms such as to pull up a skier. Over 3,000 rpm there is no problem and near 3,000 it stumbles but usually recovers.

I suspect it is the accel pump.

Also, I bypassed the inline fuel filter in case it was causing this but no improvement so I put it back in line.

Anyone have any knowledge about Demon carbs? They have a pretty good website but I cannot find the oem 2bbl marine carb listed anywhere. Having a manual would help me a great deal.

Thanks, Rich

 

[Maclin]

Re: Serious engine stumble with 3.0L 2009 Volvo with Demon 2bbl Carb

Demons are not far removed from Holleys in design and methods. As far as Marine versions, any Demon 2bbl manual or tuning guide would work for most of the settings like accel pump lever adjust, etc. If it is a "half-a-4bbl-demon" then the accel pump renew pieces should even work. Yours may have the larger volume pump, watch out for stuff like that.

Call the dealer also now, even though it has been a while and see what all the tech bulletin told them to do for the recall.

 

[Don S]

Re: Serious engine stumble with 3.0L 2009 Volvo with Demon 2bbl Carb

The inspection shouldn't have had anything to do with your starting problems. All the dealer did for the inspection is to look down the throttle bore at the screws holding the throttle plates in to make sure the screws were staked. If they weren't staked, a new carb would have been installed.
You might look to see if the choke plate is still working. if the engine was cold when the inspection was done, they would have had to open it manually. Shouldn't have done anything doing that, but who knows.

 

[YahooMarine]

Re: Serious engine stumble with 3.0L 2009 Volvo with Demon 2bbl Carb

Whatever they did involved removing the carb from the boat as all of the red paint was gone from the bolts and the linkage and around the gasket. If nothing else the carb was off the engine and perhaps turned upside down. The linkages may be involved in the issue.

The choke plate works but is at about 45 degrees whan I look at it cold. Should it be completely closed?

Thanks, Rich

 

[Susquehanna Squid]

Re: Serious engine stumble with 3.0L 2009 Volvo with Demon 2bbl Carb

My buddy had no luck with that Demon. Go back to the Holley if possible.

 

[YahooMarine]

Re: Serious engine stumble with 3.0L 2009 Volvo with Demon 2bbl Carb

Thanks for the input. After repeated attempts to get info from Demon, just yesterday I dound out that they are out of business.

So, any ideas out there? Is there a Holley drop in replacement? Did Demon possibly use a Holley oem body and modify it?

Any help will be appreciated.

Thanks, Rich

 

[Susquehanna Squid]

Re: Serious engine stumble with 3.0L 2009 Volvo with Demon 2bbl Carb

I am pretty sure that my buddy was able to switch out that Demon and install the Holley without any problems whatsoever. And, just in case you are not sure, Holley has a kit with just about every gasket type included in it.