Side mounted carbs might cause a mixture difference on the two banks with this setup. I have a carb adapter which mounts the carbs with the float bowls at the front and rear though. With no boost referencing, I've spent more than an hour in no wake zones with no loading up, and very cold plugs. This automatically gives enrichment at higher throttle openings. What I've done is remove the power valves on the mechanical secondaries, so any time the secondaries are open I have enrichment as if the power valve was open. If you are not manifold referenced you generally up your jetting subsantially to accomodate for the high RPM leanout and any part throttle and low rpm cruising ie- no wake zones, tends to load up the plugs. This is what was happening on the boats I've seen that were boost referenced, and it just caused them to run rich. or so, I could see how it would help.īut unless you're pulling manifold vacuum at cruise higher than the power valve rating, the "power enrichement" function will be defeated, and the power valve will be open all the time. I can see how it might work on a car, a boat with really small gears, or a jet boat that isn't putting much load on the engine until high rpms, any setup that has significant vacuum at part throttle. However, there is vacuum at the base of the carb above the blower, and that drops with throttle opening in similar fashion to a naturally aspirated motor, so it seems that leaving the power valve reference at the base of the carb is the best thing. That means that with boost referencing, even a low rating power valve would be open all the time. My boat never has significant vacuum in the manifold when it's in gear.
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