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Re: question about Racor fuel filter...
The smallest Racor fuel filter is rated for about 10-12 gallons per hour flow. Most small sailboat engines consume between 3/4 - 1-1/2 GPH at maximum flow - WIDE OPEN THROTTLE. Most of the 'clattertrap' you see inside Racors is to provide 'dynamic' removal of gases and contaminants from the relative HIGH VELOCITY fuel. 3/4 to 1-1/2 GPH inside a 1/4" tube is virtually 'nothing' velocity; thus, all that filter fancy-ness is of no benefit for such small flow rates of sailboat engines.
You mention occasional air captured in your fuel filter. The causes in order of severity/vulnerability are:
1. developed pin hole in the engine's lift pump - pump sucks air (from the crankcase) on the 'downstroke' (fill-stroke) of the diaphragm
2. You have 'compression fittings' installed somewhere on the 'suction side' of the fuel line .... Compression fittings are notorious 'leakers'. Fittings on fuel lines operating on vacuum should be double flared fittings with metal ring seals internal to the 'fitting'.
3. The observance of air in the filter follows a heavy sea state where the fuel in the tank is mixed into a fuel/air emulsion due to the violent shaking of the boat's fuel .... you need more baffles inside your tank.
For air removal from fuel lines due to unknown causes (until you find the problem), take ANY diesel fuel compatible filter housing (with integral drain) and install it UPSIDE DOWN and after the last filter in the 'filter train'. Any air in the tubing will be captured in the upside down housing. Since the filter, now known as a 'knock out pot' will be trapping air and will be located quite low in altitude in relation to the highest level of inlet tube from the tank .... to remove the air, ... engine off, and the fuel thus able to siphon from the tank to the knock out pot .... open the now inverted drain, the air will burp out though the drain valve when opened. Better is to install a clear 1/4" polypropylene pig tail on the drain port and with a small valve on the terminal end of the pig-tail. You will SEE the presence of air in the pigtail and will know when expel the air from the 'knock out pot'.
Before you go to all that trouble, I would offer the suggestion to carefully assay your entire fuel delivery system to find (in order as previous listed) what is the source of the air LEAK - consider to replace all those *compression fittings* with double flared connection fittint with integral metal ring seals.
Note: Good filter engineering design should include: ......Racor filters should be mounted at the LOWEST altitude of the entire fuel delivery system so that if there is an errant air leak, that air will move by air 'buoyancy' to the highest level of the fuel delivery system .... usually to the engine mounted 'engine guard' filter or back to the tank. The same principle will apply for errant water in the fuel system - wth the Racors at the lowest level of the system, drain the racors to remove the water. If you use 'cartridge type' Racors, consider to install an empty filter with drain as a water knock-out pot.
Last edited by RichH; 4 Weeks Ago at 10:53 AM.