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Message board > Engines > Fuel Primer Bulb and Fuel Line Arrangement

Message 2 of 2
Posted by member Clive ffitch on Friday 15 January 2021

Hi again,
Apart from moving the primer bulb, I also have a "standard" Quicksilver fuel filter/water separator with screw-in element but no see-through bowl and drain valve. Is it worth swapping to a filter/water separator that does have a drain?

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Message 1 of 2
Posted by member Clive ffitch on Saturday 9 January 2021

* Hi everyone,

I have a conundrum. We have two 30L fuel tanks on Adele with a Mariner 75HP 4-stroke engine, and the fuel line setup has always been "fueltank-primerbulb-fuelfilter-engine" with the need to manually disconnect and reconnect fuel tanks when swapping tanks (see "Present Set-up" in the diagram). This sequence is as it was when we bought Adele, and is indeed as recommended by a good number of sources.

Having already decided to install a manual fuel tank switchover valve to avoid the annoying and somewhat less safe swapping of fuel connections when one tank gets low or empty, I have decided to also review the position of the fuel primer bulb. Having not really questioned it before, it does take a while to prime the engine if left a while between runs, and the primer bulb never really seems to get suitably hard as you would expect, despite swapping for a new one. I can only assume partly due to the presence of the large filter unit upstream, possible air in it, the overall length of the fuel line, and very possibly the orientation of the primer bulb being horizontal. I am therefore of a mind to move the primer bulb closer to the engine, and ideally vertical, such that the setup will then be "fueltank-fuelfilter-primerbulb-engine" (see "Proposed Set-up" in the diagram, complete with switchover valve installed). This sequence is also as recommended by a good number of other sources!

I am thinking that having the primer bulb closet to the engine is the more sensible, thus making the whole priming operation far more immediate and robust, and also because the primer bulb would pull fuel through the filter, rather than trying to push fuel through it.

What does everyone else think?

Thank you in advance for your much appreciated deliberations!

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