actual orifice sizes.

[N Wolf]

I have a 1990 evinrude 120 with 63D high speed jets. It is running lean to the point that it won't get on plane with a heavy load, but once on plane it will pull 6250 RPM. I have a set of 62Ds that I obviously don't need. I wonder where I could find the sizes so that I can drill them out to 67D.

[N Wolf]

Im guessing that the 62Ds are .062 but I don't want to guess with this engine.

[wired247]

.067" . Yes, the jet size corresponds to the decimal size.

[frank jackson]

not all omc jets are size to hole size !!!!!!!!!!!!!! do not drill jets . You need 67d , get a set . Do not drill !!!!!!!!!!!!

[wired247]

not all omc jets are size to hole size !!!!!!!!!!!!!! do not drill jets . You need 67d , get a set . Do not drill !!!!!!!!!!!!

Yeah. I only played around with them for 30 years. I'm sure that somewhere outside of that range OMC stopped equating their jet sizing with decimal equivalence and starting picking random numbers.

[frank jackson]

me to 34 yrs still at it . Do not drill jets . If the owner wants to drill his jets he can , his motor . I wont argue with you or him . ......................

[wired247]

me to 34 yrs still at it . Do not drill jets . If the owner wants to drill his jets he can , his motor . I wont argue with you or him . ......................

Why not? Are you saying that OMC jet numbers arent the same as decimal numbers. I say they are. Drilling might not be the greatest way to do it. I mean you have transition in and out and appropriate angles for each but the orifice diameter IS going to be whatever OMC says it is . If the say 69 it is going to be .069" as in 100% of the time.

[racer]

D series jets are not to decimal size. C series are but they are made to flow different direction so they should never be interchanged. I don't drill jets but if you must make some larger use a reamer but much better to buy the correct jets. 62d is nearly .066 in diameter

[racer]

D series jets are not to decimal size. C series are but they are made to flow different direction so they should never be interchanged. I don't drill jets but if you must make some larger use a reamer but much better to buy the correct jets. 62d is nearly .066 in diameter

[wired247]

You buy these things called gauge pins ( www.mscdirect.com ) . If a .070" doesnt fit the hole and a .069" does fit the hole ...guess what ? Its a 69. If you drill that jet out with a .072" it will now be a 72 jet.

Iv'e drilled hundred of holleys. OMC's . carters, webers, dellorotos, and mercury's among others. Got all kinds of drilling jigs I don't even remember what they are for. Ive seen that "don't drill jets" warning over and over again. Bunch of hooey.

[powerabout]

if you just drill to tune you have jet that works, what size it actually might be to compare with another isnt the issue is it?

[wired247]

if you just drill to tune you have jet that works, what size it actually might be to compare with another isnt the issue is it?

True.

[N Wolf]

I drilled it out to .069, It was supposed to be a .067 number 51 drill but the calipers said .069. Either way, I gained nothing. With an 18 pitch prop it spun 5600 wot and slow out of the hole. Same as normal. With a 17 pitch I get 6250 wot and better hole shot. With both live wells full and a passenger in the boat, he has to climb onto the front deck to plane out. Once it does it will still spin up to 6200 rpm. Been to two shops on 4 occasions and spent thousands.

[Lockjaw]

Why not start with some information before you go crazy drilling jets. What kind of boat, prop shaft height relative to the pad or bottom of the boat, do you have a jackplate, what kind of prop?

I tend to fit into the "I don't drill jets" category. Once you drill them if they don't work, they are useless. You can't sell them in good conscience. Stock jets are flowed so you have a reference point for tuning once you drill them, you loose your reference point.

[Instigator]

The OMC "D" series jets are actually + .0055" larger than the number stamped on them. A 62D is actually .0675" I.D.

They also have a lead in taper in their entrance that causes a venturi effect. Drill out the jet, taper goes bye bye and flow is reduced.
In theory, a 60D drilled (actually .0655") to .075" will not flow as much as a virgin, OEM 69D (actually .0745") w/the taper.
I have $$$$$ of numbered bits and corresponding reamers to clean the jets up after drilling. I will only go up a couple sizes though to protect the lead in taper.
I try not to do it at all but if I only have 5 of what I need and one that is close, I'll open it up. Or when dialing in the twins......

BTW, learned all of this from racer.