Fuel lines question(s)

[Ricko99]

Hi, I am going to attempt to get some of my outboards running but I need some advice with regard to fuel line diameter, connections etc. I wondered if anyone could advise me?

(a) Evinrude Yachtwin 4hp (1987): Would this be ok to be run with a 6mm (1/4") ID fuel line? I have a tank that has a spigot this size so would like to use it for this engine.

(b) Mercury 25hp (1980/81): What size internal diameter fuel line should I use with this engine? It has the 'bayonet' type connection (I think that it is the smaller type).

(c) Yamaha 9.9hp 4-stroke: What size internal diameter fuel line should I use with this engine?

Many thanks

[Fenlander]

Looks like your first post so welcome to the forum.

If you get a fuel line that's a good fit for your existing fittings it will be fine for all those OBs. You don't want to be forcing on a hose that's too small and conversely not trying to clamp one down that's too large for the fitting.

[Ricko99]

Originally Posted by Fenlander

Looks like your first post so welcome to the forum.

If you get a fuel line that's a good fit for your existing fittings it will be fine for all those OBs. You don't want to be forcing on a hose that's too small and conversely not trying to clamp one down that's too large for the fitting.

Thanks for the welcome.

I've got 3 tanks, one with a 6mm spigot, one with a stiffened line that needs removing that I suspect is 8mm, and my large tank has a 10mm spigot. So I've got into a quandary. My logic tells me to allocate the tanks to the motors in order of hp, but I wasn't sure if a 10mm line was too big for the 25hp Mercury.

[Fenlander]

I've just looked and the hose that came with my Suzuki 20hp is 8mm, as is a universal spare hose/primer set I carry. I also have a quicksilver tank/hose but that has crimp-on hose clips so cant pop them of to check the hose size.

[Ricko99]

Originally Posted by Fenlander

I've just looked and the hose that came with my Suzuki 20hp is 8mm, as is a universal spare hose/primer set I carry. I also have a quicksilver tank/hose but that has crimp-on hose clips so cant pop them of to check the hose size.

Thanks for checking, 8mm seems standard on most these days. I'll probably remove the 10mm spigot, replace it with 8mm and go for an 8mm setup.

Cheers

[beamishken]

Theres something sadly wrong if any of those engines cant run on a 6mm hose
In reality any of the sizes would be fine

[Ricko99]

Originally Posted by beamishken

Theres something sadly wrong if any of those engines cant run on a 6mm hose
In reality any of the sizes would be fine

They're all runners (or at least they fire up), I'm just trying to match up some tanks I've got, any fuel lines I've got have gone rigid so I'm replacing them. With having a few different sizes and makes I'm just making sure I get it right.

The Mercury has the older, smaller bayonet fitting. I might try and replace it with the more modern style.

The Yamaha inlet and the Evinrude inlet look similar, are they the same?

[Lee1]

You are not alone! this is a nightmare I have experienced myself, as I use both older 1970 mercurys that the fuel connector to the engine is not compatible with the modern 8mm fuel lines that I use for later engines, so I can not just swap engine in fuel connectors to the end of the 8mm line, my solution was to fit my fuel tank to the primer with 8mm then from the primer another short 8mm that ends in a Suzuki female then I had different individual short separate fuel lines for each different Outboard fuel line diameter thus fuel in connector fitted with Suzuki male to connect to the female, it was the best quick swapped solution, now I just run mercurys on the boat so I kept 8mm to the primer then 10mm to the Mercury male You can get both 8mm and 10-12mm versions of most connectors but they are copies. I would rather use original connectors and swap fuel line to suit.
Alternatively just use 10 or 12mm fuel line for all connectors from the primer and sleeve the adapters that take 8mm with layers of heat shrink so they fit tight in the larger fuel line

Another option cheaper than Suzuki connectors is old Mercury connectors, they lock together and you can use a Mercury female after the primer on a short fuel line with your chosen adapter fuel adapter on the other end of the extension line that will have your Mercury male to connect to the female. Thus quick release and swappable this is what I have for my workshop to fit all outboards in for service etc. . Without having separate individual long fuel lines thus I can run all engines from one main line and tank by just swapping a short 6 inch fuel line with the right fuel in adapter, you could even change all your engines you will be using regardless of make to one make of fuel in adapters, that might even work out cheaper and easier if so I would use Suzuki ones.

[Poly]

Originally Posted by Lee1

Alternatively just use 10 or 12mm fuel line for all connectors from the primer and sleeve the adapters that take 8mm with layers of heat shrink so they fit tight in the larger fuel line
.

Bodged fuel line fittings, especially with materials not intended for use with fuel has the potential to look “fine” at first and then at some unexpected point in the future to fail suddenly leaving your engine stopped and you sitting is huge puddle of fuel.

[Pikey Dave]

Originally Posted by Poly

Bodged fuel line fittings, especially with materials not intended for use with fuel has the potential to look “fine” at first and then at some unexpected point in the future to fail suddenly leaving your engine stopped and you sitting is huge puddle of fuel.

[emoji106]or draw air into the fuel line as it's under negative pressure.
As an aside, I always use stainless Oetiker clips on my fuel fittings.

[Ricko99]

Thanks for all your replies and encouragement. Ive made up the first line using new fittings etc for the Evinrude using 6mm fuel pipe, new primer, new inline filter, new double ear fitting etc. I'll tackle the other engines in order of size when I get chance! I'll have to put my thinking cap on for the old Merc, I may have a go a changing the fitting to a more modern one.