OMC Tech: Crossflow Jets

**DieselDood** · 05-07-2020, 11:32 AM

Hey guys... I've got an 84 150.

Someone before me did 40 over Wiseco Pistons, and Boysen reeds and the 1 5/16 carbs.

Tonight I plan to pull the carbs down because I believe it is over jetted. Under a load I get a TON of white smoke that has VERY strong fuel smell to it, as well as under load it has a very difficult time getting past the 2800-3000rpm mark, regardless of Prop (ran 19, 21 and 23p props) I have gotten it on plane with the 23P and it ran pretty well.. I just didn't have the intestinal fortitude to run it WOT in the water conditions I had that day.

What should I expect for Jets? What do you think I should be running?
And... Where can I get them that they aren't $10 ea?! Holy crap!

**mrichartz** · 05-07-2020, 12:36 PM

$10 a piece new is good ..try eBay etc but likely cost the same
Im ordering jets and need 12 and likely more than once @ $17
Oh point of that is ive looked all over hard to find new cheaper than that.
But if someone else has post where

**DieselDood** · 05-07-2020, 12:45 PM

I'm wondering if Mikuni doesn't make a jet that is the same, and I'm sure cheaper. I've got plenty of Motorcycle and Snowmobile shops around me.

But exactly... For something that I really don't know what size I'll need, so I'll probably go one up and one down from what folks suggest, I'll be looking at 18 jets. I'd rather spend that kind of money on other things, but if the damn boat doesn't run out... it's a big paperweight!

**mrichartz** · 05-07-2020, 12:52 PM

I don't know about mikuni but racer, instigator etc might know..
And yea looking at 24 to 36
Knew the price before the build so not complaining to much.
Yea I need to do 80d/79d to start which will likely be rich then go down.. if I come across the size your looking for cheaper will post them

**DieselDood** · 05-07-2020, 01:04 PM

Thanks!
Sadly I'm not sure where to start. I'm going to have to get them apart and see where they are at now.

My suspicion is that the previous owner did the 2 sizes up for reeds and (i've read) 2 sizes up for .040. Which... could put this thing way to rich in the mid, which is where I'm having most of my trouble.

**DieselDood** · 05-07-2020, 01:05 PM

I'm not home to do any measurements... and this is all metric and the OMC stuff shows standard.... but what about these?

https://www.jetsrus.com/a_jets_by_ca...4-52_leak.html

**mrichartz** · 05-07-2020, 01:20 PM

Originally Posted by DieselDood

I'm not home to do any measurements... and this is all metric and the OMC stuff shows standard.... but what about these?

https://www.jetsrus.com/a_jets_by_ca...4-52_leak.html

Couldn't say would need one to look/measure .

**mrichartz** · 05-07-2020, 01:21 PM

Would be nice tho almost half the price

**BarryStrawn** · 05-07-2020, 01:43 PM

Suggest you identify the carb part numbers and look up the original jetting on the Evinrude online parts store. Several variations over the many years. Then compare that stock config with what you discover in the carbs and make an estimate of the direction you need to go.

**mrichartz** · 05-07-2020, 02:19 PM

Originally Posted by DieselDood

Thanks!
Sadly I'm not sure where to start. I'm going to have to get them apart and see where they are at now.

My suspicion is that the previous owner did the 2 sizes up for reeds and (i've read) 2 sizes up for .040. Which... could put this thing way to rich in the mid, which is where I'm having most of my trouble.

Oh what sizes are you looking for?
I have some just have to look at sizes.. didn't think they'd be what our looking for tho..

**DieselDood** · 05-07-2020, 02:24 PM

I'll get them torn down tonight and see what's there. Although I found out the previous owner was "old school" so what ever is stamped on the Jet may not actually be what the size actually is. I have a bunch of small drill bits, so I'm hoping I can match up the sizes to the bits and see what is there.

**DieselDood** · 05-08-2020, 07:07 AM

Holy cow.... 64D jets in my carbs currently. I tore down my 1 3/8 carbs from my other motor....same size.

Well that explains my issue...

Now... what should I go to?

**perfmarine1** · 05-08-2020, 11:23 AM

stock 1984 150 HP jet size is 58.5. Normally boyesen Reeds do not require a jet change because cross flows come through from the factory Rich to begin with. And bigger carbs on a non ported motor will probably hurt more than it helps.65C jets come in a 2.6

Best way to tell what jet size you need run at wide open for at least one minute turn the key off now if your boats really fast be dang careful, slow down a little first then turn key off. Use L77JC4 plug for jet testing

**DieselDood** · 05-08-2020, 11:25 AM

Originally Posted by perfmarine1

stock 1984 150 HP jet size is 58.5. Normally boyesen Reeds do not require a jet change because cross flows come through from the factory Rich to begin with. And bigger carbs on a non ported motor will probably hurt more than it helps.65D jets come in a 2.6

The carb part numbers say 185hp... and those are 60C's. I'm thinking I'm going to try to track some of those down

**perfmarine1** · 05-08-2020, 11:34 AM

If I remember correctly the 185 was a bubble back 235 with very low compression motor so the 60 jet size would make sense. I remember rebuilding some of those after rebuild I think the compression was only like 85 PSI