fuel tanks

[Bushwacker]

Originally Posted by martin

my tanks have 1/2 inch suction lines. I was going to have custom suction tubes made for 1/2 " then reduce to 3/8 at water seperators .. you think that is over kill

The 1/2" lines are UNDERKILL! They'll give you about 78% more flow area than the 3/8" line, but by feeding 2 engines from 1 tank you're increasing the fuel flow by 100%, so you'll still have more restriction between tank and selector valve than you'd have if you ran each engine off a separate tank with 3/8" lines! 5/8" lines (178% flow area increase!) would have been overkill! I'd check to see what size fuel lines they recommend for a 300 HP Verado. If they can feed them with a 3/8" line, you still might be ok, but the typical 2-stroke outboard lift pump, which operates off pressure pulses from the crankcase, isn't that strong, so they're pretty sensitive to flow restrictions on the suction side. I'd still recommend putting a vacuum gage between Racor exit and engine to determine how much restriction you have, and also I'd try to find out what the allowable restriction is from Mercury. The DI E-TEC motors are totally different animals from carb'd motors, so their 4" Hg limit on suction side pressure loss might not be applicable to your motors.

Wattaway - at least a total fuel blockage won't destroy your engine because it just shuts down completely. A PARTIAL blockage is more sinister because the resulting power loss is less obvious, especially on a high powered rig, where you might not even notice it until it's too late!