Re: electronic ignition conversion
Re: electronic ignition conversion
Boats never need vacuum advance because they don't have light load cruise conditions like a car. When you are in top gear out on the highway turning around 2500 rpm, you may have 10 to 16 degrees of vacuum at that rpm. It only takes a small amount of power to keep a 3000-4000 lb car at road speed thus not a lot of fuel. A boat requires a serious amount of fuel to cruise. With out getting into a deep discussion of how reciprocating engines work, in order to burn the reduced amount of fuel optimally, you have to start the fire earlier than under a high load condition. Thus the vacuum advance. A common timing program for the 5.7/ 350 Chevrolet would have the mechanical advance start at 10 to 12 degrees top dead center at idle and advance to a total of 30 to 36 degrees advance with the advance <br />all in by 3000 rpm. Now in a car application you would also have vacuum advance that could add in anywhere from six to sixteen degrees of advance on top of whatever the mechanical advance is adding in. Luckily you dont have to worry about it, as getting the ignition maps right can be time consuming. Drag race vehicles we have bulit can have what called locked out mechanical advance, but this is impractical in marine application. You would have starting problems as all that advance at crank speed make the motor kickback. Our drag motors had large enough cams that that was less of an issue. So to end this rambling mess. Do a conversion of any electronic type you like, and make sure the mechanical advance system is functioning correctly, and you should be cool.<br />JOn
