Carb Problem

[Brandenton]

My motor idles great, right around 750 RPM. Most of the time, my boat will only do 12-15mph even at WOT. While cruising at those speeds it will jump up to 30-35mph, just speratic speed chages. I have good compression, i have spark, i also have replaced all fuel hoses, fuel pump gasket and diaphram. So I tried to adjust the air mixture for both carbs on my 1984 Chrysler model 908V4B as per my manual. I didnt have any problems adjusting my top carb, but while turning the air mixture screw on the bottom carb, there was no change in the way the motor was running or sounded. So I am now assuming that I might have a vacuum leak. Whats the best way to isolate a vacuum leak on these outboards?

 

[john from md]

Re: Carb Problem

Safest way to check for a vacuum leak is to spray WD40 around the area that you suspect. You will get a change in rpm as the vacuum sucks in the fluid. WD40 is safer to use than gasoline as it's flash point is higher.

John