I always braze weld the pick-up screen to the pump housing.
Does not get too hot.
Remember to take out the pressure relief spring before brazing.
R.T.V. IMO, is horrible for oil, gas etc.
It will expand, fall off & in general will not stick all that great IMO.
I work on aircraft for a living & we use a two part sealant for most jobs, sealing windows, fuel panels etc., fuel does not affect the sealant.
http://flamemaster.com/cs-3204-class-a-b-c/We pay about $20 a tube.
And you do not need to mix it all at one time if you do not need all of it.
Refrigerate it to have a longer shelf life.
MBHD