QD15 Carb Kit – needle & seat compatibility?

[John Gragg]

I just ordered my 2nd BRP/OMC carb kit #439071 for my QD15. I have already used one kit on a spare carb I picked up, but when I did I noticed that the orifice for the seat is larger than the OEM one.

I went ahead and installed that kit in the spare carb for practice, but in my reading I’m learning that even that minute difference in size (the exact difference I’m not sure of) can possibly cause a rich issue?

I have found where Sierra 18-7094 is “supposed” to fit the bill for OEM part # 375985. But when I look up compatibility on West Marine, no mention of 375985. I ordered one for giggles, too big and same size as what is in the 439071 kit.

Do I use the new seat and hope the carb will take a tune, or reuse the old one?

Thx all

Best Regards

John Gragg
RIverside, CA

Just starting in the hobby, please be patient.

48 Sea King 5hp GG9014A
49 Sea King 5hp GG9014A
48 Johnson TD20
49 Johnson TD20
54 Johnson QD15
55 Johnson CD12

[aquasonic]

That float needle seat part number has been updated to 396522.

375985 – Part Search Results – MarineEngine.com

Having rebuilt a QD-15 carburetor with the 439071 kit, it worked fine. These kits are for many different size motors, so the larger orifice may cater to the larger horsepower, yet it still works on as low as the 3-horsepower model. I’m guessing that OMC was simplifying for the purpose of a universal kit.

 

1 user thanked author for this post.

John Gragg

[crosbyman]

curious….  but why would the needle & seat affect the carb  since  all it does is allow or block the inflow of fuel in the carb bowl.   rich or lean  is governed  by  needles or orifices  not the inlet needle point.

it is early….am  I missing something  ???

Joining AOMCI has priviledges 🙂

1 user thanked author for this post.

John Gragg

[John Gragg]

crosbyman wrote:

curious….  but why would the needle & seat affect the carb  since  all it does is allow or block the inflow of fuel in the carb bowl.   rich or lean  is governed  by  needles or orifices  not the inlet needle point.

it is early….am  I missing something  ???

Ha Ha! Nope, you’re not missing anything. I’m overthinking it, again!

LOL

Yep – Makes complete sense.

Also – I stand corrected on a point or two. I’m out in the garage right now. I measured as best I could the seat diameter for the OEM one. A 1/16″ drill bit shaft will “Just” not fit into the hole on the original seat. The newer seats in the 439071 kit will allow the 1/16″ shaft to go into the hole.  Where I am 10000% wrong and need to correct myself is the Sierra 18-7094 needle and seat appears to be an exact duplicate. The 1/16″ shaft will not go into the hole. And yes, it shows on the package that it replaces 396522, so that jives as well.

Thanks all – Worried about nothing, again!

 

Best Regards,

John Gragg
RIverside, CA

Just starting in the hobby, please be patient.

48 Sea King 5hp GG9014A
49 Sea King 5hp GG9014A
48 Johnson TD20
49 Johnson TD20
54 Johnson QD15
55 Johnson CD12

[frankr]

Some things to consider.

There were several part number changes along the way.  The original n/s had a metal needle.  That was replaced with a soft tip needle.  When the soft tip needles were found to stick in the seats of the gravity feed carbs, the little hairpin clip was added to drag it down off the seat.   The gas guzzling fat 50 and 75 hp motors had to deliver a lot more gas per minute than the smaller motors.  Whether or not that caused a larger seat, I don’t remember.

Anyhoo, bottom line is the current number is a best attempt to standardize the part.

 

[seakaye12]

I have a 12 horsepower Gale Buccaneer that has an integral tank and the carburetor seat on that motor is I would say twice the diameter of the typical OMC seat. I puzzled over that when I first saw it but I’m pretty sure it’s because that motor does not have a fuel pump since it is an integral tank and they probably wanted to ensure sufficient fuel flow as it was a 12 horsepower motor and would require a fair amount of fuel being fed by gravity.

 

[labrador-guy]

John I have run into the same question concerning those needle seats.  The two seats  18-7094 and 18-7093 one or the other has a bigger orifice.  I think the bigger one was used on the 25hp motors.  I think they could be interchangeable.

dale

They say you can’t buy happiness but you can buy another old motor, that’s pretty close!

[Author]

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