Have You Checked Your High Speed Jets

[PanRonnie]

The sulpher in the fuel could be a cause for brass corrosion !
But anyway anybody who is able to wear out it,s fuel jets should be praised as an outboard master (serious runtime)
I can be only envious about that

[Markus]

And yes, I own pin bore gauges and jet drills ...

Do you mean reamers, or are there drills for drilling “blanks”?

[Markus]

Water running over a rock will erode a grove in it over time , so why not ??

A fishing Mercury is designed for high hundreds of hours of use. Say 800.

A river can cut 1 mm of rock per year. https://www.sciencedaily.com/release...0723091822.htm

The Potomac is about 8 m deep. That’s about 11 psi of pressure at the bottom. A quite abrasive mix of water, rock and sand is flowing at around 1 m/s.

800 hours times 70 liter per hour divided by 6 jets is 9000 liters of clean fuel mixed with lubricant flowing through a jet in its life time at 3psi. It is orders of magnitude too small.

[BenKeith]

I hope anyone messing with them realizes a jet is reamed with a special tapered reamer and is not drilled. Drill a jet and you don't know how it's going to flow.
Also when cleaning them, use something like a tooth pick or wood skewers that's not going to remove metal. I am the worlds worst about just sticking a welding tip cleaner in one just to make sure it open when in doubt, but that's a big no, no. If you force it or work it back and forth, it will shave the edge and open the orifice more.

[powerabout]

Jets don’t wear out. I thought you meant something else by worn. Hence the question mark.

If the main jets are too big, they were either too big from the factory, or someone modified the engine.

Jets can get restricted as crud builds up. Crud in the main air jets will make the engine run richer. Maybe you compensated for restricted air jets by making the main jets smaller.

I have seen plenty of commercial engines with clearly worn jets that are bigger, no cartridge filters in the way...

[keith scotton]

First motor is a 1996 150 Johnson it came with 57d jets. Gets used 2 or 3 times a week all year round from new. There is no telling how many hours are on it in the thousands I would think. Jets measured 68 and larger. Old man is 70 plus not going to mess with it just pours gas and oil in it and goes. Think what you want but this does happen not usually that bad I see this most in high time motors or people who are trying to fix water in fuel problems or other problems with chemicals. A lot of them are 4 or 5 sizes larger. was just amazed at the amount of fuel being used. People with Trailer queens will never see this. I have been working on Boats for a Living from 1976 to date.
Enjoy Life Keith

[flabum1017]

Maybe someone bead blasted the carbs with the jets in...........

[Chaz]

Water running over a rock will erode a grove in it over time , so why not ??

If ya gotz a couple thousand years to wait .. yea OK ..

Markie, come to think of it I have a small ream set too .. Look at the chart , like i said .. way more to it than orifice size ...

But if that's all you can deal with ... Use this orifice area calculation :



BTW, carbs meter fuel on a vacuum signal , not PSI ....

[flabum1017]

BTW, carbs meter fuel on a vacuum signal , not PSI ....

Yup, that's why a motor making 400 HP at 4,000 RPM uses different size jets as a motor making 400HP at 7,000 RPM.......

[frank jackson]

Brass is alot softer than rock , you do not need as much time to wear it away .......

[Chaz]

Brass is alot softer than rock , you do not need as much time to wear it away .......

So do the reed cages and ports erode away as well ... ????

500 years and it should be "nature ported" ..

How long till this no longer keeps accurate time ... thru erosion ...

[Dave S]

Ya but glass is just melted sand so it's not going to wear out like gas will a jet...... Com'n man.

[tlwjkw]

something "new" at tha top of tha "heard it all" list......................

my stuff is way to fat?.. wore out jets!

[flabum1017]

Brass is alot softer than rock , you do not need as much time to wear it away .......

A river is lot different than the inside of a fuel system..... river has a lot of abrasives; sand, pebbles, silt etc.... Grand Canyon took millions of years to get to where it is today. Unless the fuel is very dirty, it will not erode brass jets. Corrosion from water in the carbs is a different story tho, thanks to ethanol in the fuel that absorbs water; this is why it is strongly recommended to use non-ethanol fuel in your boats and yard equipment (and older pre-ethanol cars). From what I know (if it's still true) ethanol blended gas is illegal in airplanes...... Like I pointed out earlier.... someone could have bead blasted the carbs.... a lot of guys down here do it to get the corrosion out of the bowls..... some even use toilet bowl cleaner which can cause electrolosys problems if the jets are left in.....

[Merc 2.5]

Ya I just dont see how gas (fuel) can wear a hole larger in a brass fitting (jet) , yes if u get smaller jets you will get better gas mileage, but u better have it right with the smaller jets if u gonna hold it wot , in other words , sumthin abrasive would have to "open" the jets , not the fuel