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NS8B Carburetor question...

Eric.C

Contributing Member
We were looking for a bit more power out of our 1998 NS8B, so I figured I would give the NS9.8B jets a shot. I saw a post somewhere else to swap out the slow jet, main jet, and main nozzle to un-de-tune it to a 9.8hp. I realize being an older motor, we may run into issues with running rich, but it is worth a shot. Easy enough to swap back if we start fouling plugs or anything.

My question is: what's the deal with the rubber plug on the slow jet???? I'm not a carburetor guru, but it sure seems to me like the plug completely blocks off the slow jet? I am a tech, but not 100% sure about this thing. Asked the opinion of an "older" tech at my work, and he agreed it seems odd. Maybe part of the de-tuning kit? Consensus was to leave it out and see how it runs. We will not be using the motor again until next weekend, so I figured I would ask around here in the mean time. Thoughts?

EDIT: Oh, and thank you in advance! :)
 
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No. Do not change jets. That will make it run way too rich. The carb for a 9.8 is bigger all around, including the venturi, and that is why it runs bigger jets. Depending on your serial number, the blocks are different between the 8 and 9.8, so you probably already have as much hp as possible.

You need the rubber plug. You only remove it for access to the jet. In normal operation, the fuel supply for that jet first passes through the main jet. If you try to run with it out, the motor will load up with fuel, and may not even run.
 
Hmm... What about better reed valves or something then? We don't have the funds to get a new motor, but we need a bit more power. With two guys and 10 hoop nets on the dinghy, we cannot plane out. Makes bugging an excursion. Once the nets are off, we can, but heading in and out of the harbor with the nets is slow-moving.
 
Eric,

I'm afraid that you have as much as that motor can reasonably do. Aftermarket reeds might help a little, but idle will suffer, and they tend to spit a little more. So, the short answer is that you need a bigger motor.
 
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