The Offshore Voyaging Reference Site

Carry Spare Banjo Fitting Washers

Banjo fittings are ubiquitous on engines (there are a lot of them around, too), usually in the fuel system, but the fresh water cooling circuit often has a few as well.

And each of them has a small copper washer each side of the fitting that acts as a seal.

Here’s the thing: the washers are not reusable…but most people do, including many professional mechanics who should know better.

Which is why a lot of engines are plagued with leaks.

So it makes a lot of sense to carry a few of each size. We could buy them one by one or we can buy a lifetime supply over at McMaster-Carr.

Thanks to my friend Wilson, who warned me about this when we bought the J/109, so I had the right washer to hand when the engine started pissing diesel fuel.

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Bill Arbaugh

You should also check the banjo fittings prior to the primary filter for debris periodically. I know of one boat that lost power because debris had built-up in the fitting. I took mine off, newer boat, and there was tank debris stuck in the fitting.

Wilson Fitt

The banjo fittings on my little Yanmar 3GM30 are a complete PITA. They have leaked to a greater or lesser extent almost from new. Replacing the washers helps for a little while but the bolts seem to work loose from vibration and tightening them work hardens the copper. Basically, I put up with leaks and replace the washers whenever there is cause to take the system apart. Many thanks to John for sharing some of his lifetime supply.

Also on those engines, the basin that holds the secondary fuel filter is held on by a knurled collar and sealed by an O-ring that leaks too. A fatter than standard O-ring slows this down but does not prevent it. The filter body is aluminum so over enthusiastic tightening of the bleed screw will strip the thread.

Did I say that it is a PITA? However, the little engine has pushed us a very long distance with very little complaining so we are fond of it in spite of its failings.


Dan Perrott

We have just started using dowty washers on our banjo bolts. (Also called bonded washers).
They have a rubber seal inside the washer. Rubber provides the seal,metal stops the rubber being over compressed.
Apparently they can provide a better seal. They should be reusable. Haven’t used them long enough to say they are fantastic or not.
They would very useful if chasing problems and having to take fittings on and off more often. Slightly more expensive but still pennies.
Worth trying if having sealing issues.

William Murdoch

Wilson Fitt said “The filter body [on the engine] is aluminum so over enthusiastic tightening of the bleed screw will strip the thread.”

I stripped mine out with no replacement available when I tried to stop a persistent leak at that spot. In one trip to the hardware store, I bought a 1/8″ brass needle valve with NPT male ends, a 1/8″ NPT tap, a female 1/8″ NPT to 1/4″ compression fitting, and a foot of 1/4″ copper tubing. I tapped out the stripped hole, screwed in the valve, added the fitting and tubing with a 180 degree bend in the tubing so its open end pointed down.

To bleed the fuel filter I hold a dry empty PET water bottle under the tubing, open the valve, and let a couple of ounces of fuel flow before closing the valve. I pour the fuel back in to the tank so there is little mess to clean up.

The replacement filter assembly I later bought has been under the port settee with the other spares for at least fifteen years.

Colin Speedie

Hi Wilson
I had exactly the same problem with the bleed washer, until I spoke to Cellar Marine, legendary Yanmar dealers in Cornwall and they told me that the bleed washer should be some form of plastic, not copper. I only had a fibre washer, so used that until I can’t one in the right plastic, and the leak has gone…
Best wishes

Nojan Moshiri

This is such good advice. Small, cheap item that can really upend cruising plans.

We found ourselves stuck in the sea of Cortez for want of a few of these washers after a fuel line issue. Luckily a cruiser was able to slip them in their luggage and get them to us , but at great expense for overnight shipping and the loss of week or more of time.

If we had been more remote it would’ve been even more annoying.

Neil McCubbin

Agreed that they are desirable spares, but how to know what sizes without dismantling a lot of perfectly tight joints?
The parts manual for our Beta 60 lists manufacturer’s part numbers, at $$$
The good news is that there are substantially fewer banjo connections than our late and unlamented Volvo

Paul Fleming

John my good man. Learn something new everyday. This one is a gem.

I can no other answer make but thanks,
And thanks, and ever thanks.
(Twelfth Night)

William Murdoch

Of course, best practice is to fit a new copper crush washer every time a banjo fitting is opened. But if forced by circumstances the washers can be reused by re-annealing them and smoothing their surface. Heat them in a propane flame until they glow bright red, let them cool in air or water, then sand away the resulting black copper oxide and any ridges or rings in the surface with fine sandpaper to give two clean smooth surfaces without visible scratches. It will get you home.

James Evans

I was taught, back in the day when I rode leaky British motorbikes, that the right way to anneal a copper washer was to heat it to bright red then drop it edge-on into cold water. On the other hand, I rode leaky motorbikes.

Ben Garvey

This is exactly right. I have done this more than once when fixing leaks in remote places. I can attest that this works – had to do this with the washers under a set of injectors on an ancient Perkins; and again on the fuel pump of another Perkins. not hard to do at all and dangit, it fixed the leaks… in fact i think one of them is still in place and running strong on my own boat.

…but yea… probably wise to buy and stock a few replacements!

Colin Speedie

In my day with leaky BSA/Triumph motorcycles, wee annealed head gaskets again and again and it worked every time.

David Nutt

I was pleased to see there is a comment here about annealing the copper washers. My preference would be a new one but during our circumnavigation on Danza I found myself in need of a new washer. I was grateful for the years I spent as a child in the engine room on my father’s schooner and some of the tricks of the trade I absorbed from those times.

Hans Boebs

I was taught that you can use aluminium washers in place of the copper ones and these can be reused without any heat treatment. But I must confess that I never did that. I always carry plenty of spare washers, both copper and aluminium and where I found copper ones I replaced with copper.