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Fuel primer bulb location

Printed From: The Fishing Website
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=137835
Printed Date: 04 Jun 2026 at 9:57pm


Topic: Fuel primer bulb location
Posted By: Haularse
Subject: Fuel primer bulb location
Date Posted: 06 Sep 2023 at 8:37pm
Hi Folk's, in you opinion where is the best place to have a fuel primer bulb located.
Before or after the fuel filter?

Mine has been placed after the filter, tonight when I pumped it there doesn't seem to be any fuel coming through, feels empty even after a five minutes of trying. Inlet and outlet fuel flow direction into the filter is ok as is the flow direction of the primer bulb.

Have a tote tank, around three feet of fuel line to the filter, filter to primer bulb around 2 feet.

All brand new at last service.

Thanks for your input.


Replies:
Posted By: Fish Addict
Date Posted: 06 Sep 2023 at 10:59pm
Manufacturers recommend the fuel primer bulb be located between the filter and the motor.

Posted By: Pcj
Date Posted: 07 Sep 2023 at 1:36am
I asked at last service about water separator/filter.  He said you're running tote tank no need to filter, presuming you fill tanks regularly. His claim was primer pump gets initial fuel to motor and engine pump may struggle with extra resisdencevia filter.   Asked another outboard mechanic and he agreed . But if I had inbuilt tank then filter required, surely would run in to same residence unless different pump fitted??

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"Times up"

Posted By: Haularse
Date Posted: 07 Sep 2023 at 5:06am
Thanks for the reply, will run it Friday after work on muffs and see if the fuel gets drawn through ok.

Started using fuel filters years ago after getting water in my tote tank when filling up at a service station. They were having a fuel delivery at the time and the fuel being dumped in had stired up crap from the bottom of the tank and ended up (unknowingly) with some water and crud in my fuel tank. 
Enough to stop the (engine and make it run rough) in the Wellington harbour entrance and limp back to the ramp. Ever since then, in every boat I have owned have run a seperate fuel filter as a precaution. 

That is why if you ever see a service station getting a fuel delivery and you need to buy fuel, strongly suggest you go past it and find another one. 

Posted By: kimber7wsm
Date Posted: 07 Sep 2023 at 5:17am
Sometimes the bulb itself plays up. On a boat I had to get it to work, I had to take the hose off at a joint after the bulb. Then I would put a finger over the hose, when I unsqueezed the bulb. This allowed fuel to suck through, which it wasn't previously. I kept doing this until I had fuel coming out of the hose, then I joined it back up and it ran perfectly. That showed me I had to replace the bulb. The non-return valve wasn't working.

Finger not over hose when squeezing, finger over hose when unsqueezing.

Hopefully the method described, makes sense.

Posted By: krow
Date Posted: 07 Sep 2023 at 8:17pm
I've had the bulb internals perish and small bits of rubber go into the fuel line. Visible in the filter glass. Mine is before the filter. Been like that for many years and a couple of boats. I suspect the "recommendations" from the filter point of view is so that the filter that is designed to work under vacuum isn't over pressurised and thus blowing a seal. I see one advantage of having the pump after the filter. You could see if the filter is blocked because the pump would be sucked flat.
The pumps certainly don't last forever and I'm about to replace mine as it's got firmer and harder to squeeze. Also they pump better if the directional arrow is pointing up. 
I would recommend having a filter and water trap even if just running on totes. Engines these days are very sensitive to water in the fuel. In my tool kit I carry a small (100mm) length of SS tube so that if the filter blocks, Glass gets smashed or seals fail I can in an emergency bypass it. I carry a spare pump too. 

Posted By: ohsif
Date Posted: 08 Sep 2023 at 7:03am
Try holding the primer bulb vertical with the outlet at the top. This allows the non return valve to work better.

Posted By: Haularse
Date Posted: 08 Sep 2023 at 5:59pm
Thanks for your input everyone.

Started the motor, ran instantly with the primer bulb feeling hard right away indicating fuel being sucked through without having to pump the bulb.

Again thanks for taking the time to reply.

Cheers

Barry

Posted By: krow
Date Posted: 08 Sep 2023 at 7:31pm
Hi Barry the fuel bulb shouldn't be hard with engine running, after long enough to undo what you have pumped. Engine fuel pump sucks fuel so bulb should be in its natural full of fuel state. If it's hard it's past it's use by date and needs replacing. 

Posted By: Pcj
Date Posted: 31 Dec 2023 at 5:21pm
Had fuel issue Saturday,couldnt get above 3800rpm which is my normal cruise,found that the bulb with omc fitting was trying to suck air and fuel,swapped it today for johnson/evirude and very snug fit,despite what being told ,no need fuel water trap running on totes,fitted one any way,then thought what about fuses,Hmm 1 20amp is all the motor has so brought a pack,What about spare plugs "Paul" repco yes but not $49.95 each BUHW-2

Wednesday job,prompt part $12.50 each, no plugs at smartmarine or burnsco. one  does wonder why when they sell oil etc.




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"Times up"

Posted By: krow
Date Posted: 01 Jan 2024 at 8:25pm
I don't think too many people have "issues" with their filters, including me. Mine is some sort of see through plastic with a small drain plug to drain any water this could be broken off or some other failure so I carry a small tube of SS in the tool kit that I can reconnect the in and out hose of the filter should something go wrong with it.  Just a thought.


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