Re: Merc 400 Fuel Lines
Been awhile but those interconnect fittings use(d) "pre assembled" hose barbs/reinforced rubber hoses.
The thread on these fittings is 1/8-1/4" pipe (don't remember) but the pipe thread is tapered and is brass whereas the female part is aluminum cast material which usually has some porosity which could cause leaking problems. It (the pipe fitting) is designed to wedge it'self into the female and thus provide a locking mechanism when the connection tightens up.
On low pressure installations, like fuel delivery systems which are usually less than 10psig for carbureted engines, sealants aren't that important........butttttt a little fuel resistant pipe joint compound (hardware stores have it) keeps you from having to worry about it and lubricates the threads which helps in getting a good snug joint.
Interesting that Merc did that for years and finally, when the nylon tie wrap came into being, replaced them with hose barbs, tie wraps, and non reinforced rubber hose.....saved them a ton of money, worked just fine, and was much easier on the installation/repair folks.
Mark
