Have You Checked Your High Speed Jets

**phillnjack** · 01-20-2021, 07:08 AM

yes water will erode a rock over a few hundred years. also water is a lot harder than petrol..
for it to go up 11 sizes would need to be put on some mega high pressures that the carb bowl seals would not handle....

11 sizes up tells me they have been enlarged by drill or reamed out. NOT fuel erosion.

just my thoughts.

**Chaz** · 01-21-2021, 06:31 PM

Originally Posted by flabum1017

Vacuum sucks, eh Chaz?

In a word ..... yes

So now we have heard it from Florida to California. North to Canada and half way around the world to England ... with stops in between ...

They say if three or more people call you a horse, you should go saddle shoppin ...

Chaz = waitin on a thank you

for all of us who tried ..

**flabum1017** · 01-21-2021, 08:36 PM

Originally Posted by Chaz

In a word ..... yes

So now we have heard it from Florida to California. North to Canada and half way around the world to England ... with stops in between ...

They say if three or more people call you a horse, you should go saddle shoppin ...

Chaz = waitin on a thank you

for all of us who tried ..

Have a feeling a carburetor jet will erode before you get your recognition

**Chaz** · 01-21-2021, 11:14 PM

Originally Posted by flabum1017

Have a feeling a carburetor jet will erode before you get your recognition

Chaz = thinkin , it might get to double the size and be as big as .022 large by then ..

Just thinking out loud .. .079 would = .004902"

**rude tim** · 01-25-2021, 01:16 AM

Originally Posted by Smalltownbassin

Ive been following this post for weeks! Im always learning from you fellas, even if its in the "meh" category it's still good stuff. Tim, i only quoted you because i was asking myself the same question until i related it to something i deal with daily in a different application. Without thinking in terms of "pressure" & "vacuum" because they muddy up the water, think more about the volume of material moved through the orifice. After all, even a carb bowl can be considered to be under pressure if there is less (vacuum) on the other side. All a vacuum is is a pressure differential right? Anyway, back to my stupid, troublesome, heap of scrap metal i call a 3d printer. This is a more extreme example of your comparison between a carb jet under vacuum and high pressure injector. Im always running high abrasive material like GF or CF that are determined to destroy the nozzle asap. I typically use a 0.6mm orifice but often, for more precise work, use a 0.2mm. This plastic is squeezed through at extremely high pressure but much less so with the larger orifice. Ive noticed that no matter what size nozzle im using, the abrasive wear is the same because the distance traveled is the same. This is how im thinking when it comes to your question. It seems like the only big factor is the amount of material moved. The more abrasive material is moved through an orifice the more it wears the orifice. Has nothing to do with whether its pushed or pulled through. Dont take my word for it though. Its just a thought. Chaz will gladly tell me where im wrong but thats what makes this fun.

I never thought of it that way, thanks for the explanation.

**loop** · 02-08-2021, 12:22 AM

Keith Scotton asked me to take a closer look at the jets in question and them to compare to a couple of others.

I took 3 jets to check out so the first thing i did was rinse them in mineral spirits the blow them dry with compressed shop air. Then I measured them with pin gages. These are my findings
one brand new,never used 59D jet. It measured .0595-.059"
one used (unknown hours) 62D jet. It measured .063"
one worn 59D jet. It measured .071", Approximately .012" over the size stamped on it. This is one of the jets that prompted him to start this thread.

also worth noting is that there was no measurable taper in the orifice of any of the jets. The machining marks also indicate that the holes were reamed with a straight reamer.

Just for reference i also measured the inlet/out of each one
The new 59D and used 62D both measured .112-.113" on both ends.
The worn 59D measured .121-.123". About.010" larger than the other two

I then milled each one in half lengthwise to expose the metering orifice as well as the inlet and outlet. I viewed them and took pictures with my Iphone looking thru a magnifying glass. Pretty crude I know but its all I had.
The new 59D as expected was shiny and gold with machining marks evident on all surfaces. Corners and edges were sharp and crisp.
The used 62D had a dull yellow finish but machining marks were still very noticeable. Also had sharp and crisp edges and corners.
The worn 59D had a bright gold color but the surface finish resembled a fresh glass bead finish. There are NO machining marks visible on any of the internal surfaces and the edges and corners were slightly rounded over and less sharp and crisp than the others.

Hopefully the measurements and pictures will help you all to see that theres something very unusual about the jet that Keith was talking about. I dont believe that its a coincidence that the orifice and the inlet/outlets are both .010-.012" larger than the other examples.

I remember reading years ago that certain additives in newer gear lubes will attack the brass and bronze parts inside older car and truck manual transmissions and transfer cases. I looked it up and found out that the chemicals that are harmful are phosphorous and sulfur and and they are found in at least one popular 2 stroke outboard oil.

I'm happy to answer any questions about what I found.

https://www.machinerylubrication.com...itives-effects

https://bobistheoilguy.com/forums/th...cle-oil.35692/

Interesting too that this thread about the Pennzoil also mentions that BMW claims sulfur is doesnt play well with Nikasil plating.

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New 59D

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Used 62D

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New59D and worn 59D

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new 59D andworn59D (different lighting)

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worn 59D closeup

**flabum1017** · 02-08-2021, 06:56 AM

Then it's just as we have been saying all along, this could not happen without an abrasive causing the erosion or something such as water or another reactive chemical causing electrolysis or corrosion.

**loop** · 02-08-2021, 07:15 AM

yes a chemical reaction would be my guess but I'm not a chemist or metallurgist so take that for what its worth.

I'm just glad that Keith shared his experience for everyones benefit. There were other theories offered by other people too.
He only offered his guess as to what caused it but enlisted my help to figure out why. After all its easy to find a problem but finding a solution to the problem is more difficult.

**flabum1017** · 02-08-2021, 07:41 AM

Not saying you're wrong to assume it was what's in the oil, but with all the guys here that use Pennzoil, you would think we would see a lot more of this problem.

**loop** · 02-08-2021, 10:23 AM

The only thing I feel 99.9% sure of is that the orifice wasnt opened up by any traditional means like drilling or reaming. But I still dont KNOW what caused it and i'd love to hear more thoughts about it now that we haave a better idea of what they look like.

one thing I forgot to mention was thaat none of the sample jets had been cleaned by abrasive blasting.

In all fairness to Keith,his ssecond post (#7) mentions outboard oil as possibly contributing to this.
Ive been using the either the Pennzoil semi synthetic or the XLF version almost exclusively for probably 15 years. Its come highly recomended by some respectable engine builders. After seeing this I will most DEFINITELY been checking my jets and thats exactly what he was pointing out to us. I would hope that any performance oriented boater would do the same

**flabum1017** · 02-08-2021, 12:16 PM

Originally Posted by loop

The only thing I feel 99.9% sure of is that the orifice wasnt opened up by any traditional means like drilling or reaming. But I still dont KNOW what caused it and i'd love to hear more thoughts about it now that we haave a better idea of what they look like.

one thing I forgot to mention was thaat none of the sample jets had been cleaned by abrasive blasting.

In all fairness to Keith,his ssecond post (#7) mentions outboard oil as possibly contributing to this.
Ive been using the either the Pennzoil semi synthetic or the XLF version almost exclusively for probably 15 years. Its come highly recomended by some respectable engine builders. After seeing this I will most DEFINITELY been checking my jets and thats exactly what he was pointing out to us. I would hope that any performance oriented boater would do the same

What gets me is how straight the bore is all the way through. Generally with erosion or corrosion, you would not see such uniformity. there would be pits and the bore would not be as consistent as it is. I would wager someone had bored those jets larger and whatever etched them did so on a much smaller extent.

**PanRonnie** · 02-08-2021, 12:32 PM

There used to be a time you were in complete control off your jet size before somebody decided it was a bad idea.

I think the moral of the story is you should always check stuff yourself not rely on somebody else or what they tell you!
If i would have done that before i put in my brand-new FiveO motorsports injectors i would probably not have trashed a piston

as far as corrosion pick your poison

**tlwjkw** · 02-08-2021, 12:45 PM

really don't understand what ya'll are "assuming"???.. if ya don't have an original, checked at tha very first start number ya'll are jus guessin' on wear n tare/erosion measured years later.. given tha outboard "quality control" you don't have a clue as to what they started out at.......... jmo.

**keith scotton** · 02-08-2021, 01:04 PM

The Jet in the picture is out the second motor I have seen from the start of this posting second customer did not even know what a jet was. Jets are marked at the factory and as stated by racer will run one or two sizes larger than marked. These motors have water separators. I have been seeing this for a long time. Most of the time on 60 degree v6 but have seen this on other OMC-BRP Products.

**keith scotton** · 02-08-2021, 01:12 PM

The Jet in the picture is out the second motor I have seen from the start of this posting second customer did not even know what a jet was. Jets are marked at the factory and as stated by racer will run one or two sizes larger than marked. These motors have water separators. I have been seeing this for a long time 10 plus years. Most of the time on 60 degree v6 but have seen this on other OMC-BRP Products. .070 is not a common drill size you can buy at the home depot of the rack. If you look at the jet the inlet and outlet are larger as is the taper to the bore.