fuel filter / water separator
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Category: General Forums
Forum Name: The Boat Shed
Forum Description: Discuss all things boating.
URL: https://www.fishing.net.nz/forum/forum_posts.asp?TID=134283
Printed Date: 03 Jul 2026 at 8:17am
Topic: fuel filter / water separator
Posted By: edge01
Subject: fuel filter / water separator
Date Posted: 21 Sep 2020 at 8:16am
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Hi Lads, this is a bit of a technical question. My dads launch has a small water fuel separator which works fine, but is an absolute bitch to change the filters in. Im thinking about making a new one out of stainless for him using some parts of the old one ( the glass water separator parts) and a new spin on style nut top with a much larger filter cartridge inside. My question is this. If i make it out of stainless will that affect anything with electrolysis in the engine or anything?? dis simmilar metals and all that. It wont be mounted on the engine. It mounts on a bulkhead of the fibreglass in the engine room. Boat holds about 1200 l of fuel. steps maybe you can help?? just want to be sure before we go ahead and do this k
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Replies:
Posted By: SaltyC
Date Posted: 21 Sep 2020 at 9:28am
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are the fuel lines copper or rubber all the way to the motor? Some older boats will still have copper fuel lines at least some of the way. Normally there will be at least one section that is rubber before the line hits the lift pump/injector pump, if so then there should be no electrical connection between the seperator and the engine so no issue. I have stainless fuel tanks, steel water separator but rubber fuel lines, all effectively isolated by the fuel lines.
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Posted By: Steps
Date Posted: 21 Sep 2020 at 10:01am
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Above pretty well nails everything.. Im a huge fan of making my own stuff... but somethings are just not worth it in time and cost. eg its far cheaper to bu a cheap new red shed smoker and modify seals lpg regulator and out let than build one out of a fridge or even old timber..  Im out of my depth here when get to 1200L fuel tanks...And large engine fuel volume flows..ie fuel line ID size. My thoughts are: And stand to be corrected on anything here.. big tank thats a larger area for water to hold on the bottom, potential for more than expected. So take the opportunity to increase the filter capacity size if need be.. Fuel flow.. this is so damn critical... just go over sized ID .. Side note, digress here, it is not always the case to go bigger thu. Things like a 1/4 mile car may get starvation and think it is because of small fuel ID size. When , and far too often, it is the mass of the fuel in the over sized line, that under high acceleration, is too great for the 'over sized' fuel pump to over come Electrolysis: If isolated (above post) nps.. I think.. maybe.. if 'connected ' to engine with stainless being a 'distance ' from alloy on the corrosion factor lists there could be an issue with alloy parts on the long term. Google for metal corrosion list.. should get you to a list of conductive metals .. on the list the further apart they are on the list the more, corrosion...just a bit of general info that may come in use someday. Sort explains why a sacrificial anod is further away than the item you wish to protect and why the anod dissolves 1st. Edit: every time you change a filter, be it a car oil sump, fuel what ever, always open it up and see what is in there...a Quick check can easy save you 10s of 1000s dollars. |
Posted By: edge01
Date Posted: 21 Sep 2020 at 6:32pm
| Yeah ok thanks for your help. The fuel lines are copper but the fuel filter is separated by heavy duty rubber fuel line with crimped fittings. It's big. About one inch od |
Posted By: Steps
Date Posted: 22 Sep 2020 at 8:26am
Sweet so long as when put the throttle down it doesn't do a 10 sec 440m hole shot 
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Posted By: krow
Date Posted: 22 Sep 2020 at 8:49pm
| As long as you can still see whats going on and can seal it. If it's on the suction side beware of dodgy seal and sucking air. |