exhaust flappers

mikemj

Cadet
Joined
Jul 7, 2015
Messages
14
I have a 2000 fourwinns with a volvo 4,3gl perfs sx drive(black).Have a wot issue .when going to 3/4 to full throttle motor just bogs, back off throttle and goes great from 1/2 to 3/4throttle .everything from timing to ignition to carb(new holley 2300) have been gone thru and or replaced.Can a ignition module from a auto version be the possibility.not sure how the engine advances timing.was reading forum and there could be a maybe its the exhaust flappers,but im not sure if this engine even came with them,if so where r they located.thanks greatly appriciated
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,306
Volvo quit using flappers shoetly after the started

Check your accelerator pump
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,468
Ayuh,.... Welcome Aboard,.... Yer symptoms suggest a lack of fuel flow at higher rpms,....

Ya rebuilt the carb, is the fuel pump pushin' 4 to 6 psi,..??
Is the line, 'n fittin's at the tank clear,..??
Are ya Sure ya got the carb Right,..??
 

skydiveD30571

Lieutenant Junior Grade
Joined
Feb 13, 2012
Messages
1,042
Volvo quit building motors with exhaust flappers in the late 90's. Being that boat year and engine year are commonly different, you could have flappers. Whether that is the cause of your problems, well that's a different story. See this link for info on the flappers and removal.

http://marinemechanic.com/volvo/volvo/2010/25-2-5A[1]exhaustflapper.pdf
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
11,802
The flappers they used are the same as the ones used on the OMC Cobra and they only cause a problem if you had an over heat in the past that melted them, that would cause them to fall down into the exhaust pipe and they could possibly block the exhaust. Volvo said that they didn't think they were necessary, not sure if this is true or not, but they did stop installing them after a certain date. I had an overheat on my Cobra and had to fish one out of the exhaust housing in the transom mount, had to remove the drive to get it out with a coat hanger wire. If it did have flappers they would be right at the top of the exhaust Y pipe, but you can't see them unless you remove the riser hoses top and bottom and the 90* exhaust elbow that connects them.

4.3 Center Riser Exhaust Conversion.jpgfrom i phone 302.JPG
 
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