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Honda 9.9 air bubbles

Frolic

New member
Im getting bubbles from the 4 small holes above the cavation plate at all power settings....what are these holes for? good water flow from P hole runs fine...
 

jgmo

Silver Medal Contributor
Hi Frolic,

Approximately how old is your outboard? The 9.9 has been around for decades.

I have to say that I'm no expert on this subject and the Honda shop manuals I've read don't really address it. So, just consider this a discussion and it might prompt someone that really has the "scoop" to jump in and teach us both something.

I believe those little holes act primarily as drains for the exhaust side of the extension case.

Not sure what is causing the bubbles but could be that you have something wrapped up around, behind or in the prop that is restricting the exhaust flow. Just a guess though.

The exhaust is supposed to be mixed with water from the cooling system and I suppose a problem with that "system" might also result in bubbles down there.

Up top on the BF9.9 D model is the "exhaust chamber"
(See link below) and I'm not sure what would happen if that big old gasket got a big tear in it.


Hopefully someone else here has a more precise answer for you.

Please let us know what you find and good luck.
 

Frolic

New member
Im getting bubbles from the 4 small holes above the cavation plate at all power settings....what are these holes for? good water flow from P hole runs fine...
Interesting info. Perhaps I’ll pull the prop and check for debris. I have had seaweed around it several times. Let you know
 

jgmo

Silver Medal Contributor
I've seen where people talk about the extension case seal going bad and causing bubbles down below too. Not sure how that works but just tossing it out there..
 

GadgetGeek

New member
I noticed an extraordinary amount of bubbles today on my 2021 Honda 9.9 as well. The engine is running great when in neutral. Any throttle in gear bogs it down, and it cuts off. I can use the engine at low speeds in gear, controlling it with the choke.

I must constantly clean the P hole with a thick piece of mono to clean out the salt. It is flowing great today.

Today I replaced the plugs and pulled the carb to soak. I also replaced the in-line fuel filter to see if I can get things cleaned up so I can use the throttle to drive and not only the choke.

I had manually cleaned the carb last week and it helped slightly. Hopefully, dunking it for 8 hours will clean up the rest that I must have missed.
 

jgmo

Silver Medal Contributor
Hi,
Here's my take on what you've stated...
I think you're probably correct about the carb needing additional attention for your power issue. I hope the solvent you're soaking in doesn't damage the plastic parts on the carb though.
I've cleaned many of these carbs and I've always used "carb spray" with excellent results. But...I was warned by a VERY experienced and knowledgeable Honda tech that not all "carb spray" is of the same formula and he said I was probably getting away with not damaging the carb because I'm in California. His shop was in Ohio and his username here was the much respected hondadude. He recommended using brake kleener spray instead.

Your 9.9D model has an accelerator pump system under that little rubber bellows on the side. It supplies a passage in the main carb body that feeds a brass tube that juts out into the air stream at the front of the carb throat. When cleaning the carb you MUST find the very tiny spray nozzle at the end of that tube that faces rearward and sprays fuel on initial throttle application.

You can only observe that spray orifice through the rear of the carb throat when the throttle linkage is held/propped wide open.
If that nozzle won't spray a stream of pressurized cleaner out the rear of the carb to a distance of 6 to 8 feet....YES!...6 to 8 FEET... then your outboard will never make full power or run well.

For your P hole plugging constantly, you will likely need to remove the right side lower cover, take off the P hole delivery tube and then remove the fitting for that tube from the engine block and briefly start the outboard. Anything trapped in there (that you're likely just shoving down with the trimmer string) will be almost instantly ejected by the force of the stream. It gets everything wet but if you submerge the outboard in a trashcan of fresh water it won't hurry anything and reliably clears that passage. That is....until the next time. All small outboards will eventually need this little operation from time to time. Or...you can keep using the fairly ineffective string trimmer line over and over and over.
Warning!...
...before removing the lower cover study the routing of that little tube VERY carefully. If not reinstalled in the correct way. It can be pinched when you reinstall the cover.
That little tube is supposed to be soft and flexible. If it isn't, it will catch small debris and plug too. It can drive you mad.
I replace that tube every 3 or four seasons on mine for that reason.
Good luck.
 

GadgetGeek

New member
Hi,
Here's my take on what you've stated...
I think you're probably correct about the carb needing additional attention for your power issue. I hope the solvent you're soaking in doesn't damage the plastic parts on the carb though.
I've cleaned many of these carbs and I've always used "carb spray" with excellent results. But...I was warned by a VERY experienced and knowledgeable Honda tech that not all "carb spray" is of the same formula and he said I was probably getting away with not damaging the carb because I'm in California. His shop was in Ohio and his username here was the much respected hondadude. He recommended using brake kleener spray instead.

Your 9.9D model has an accelerator pump system under that little rubber bellows on the side. It supplies a passage in the main carb body that feeds a brass tube that juts out into the air stream at the front of the carb throat. When cleaning the carb you MUST find the very tiny spray nozzle at the end of that tube that faces rearward and sprays fuel on initial throttle application.

You can only observe that spray orifice through the rear of the carb throat when the throttle linkage is held/propped wide open.
If that nozzle won't spray a stream of pressurized cleaner out the rear of the carb to a distance of 6 to 8 feet....YES!...6 to 8 FEET... then your outboard will never make full power or run well.

For your P hole plugging constantly, you will likely need to remove the right side lower cover, take off the P hole delivery tube and then remove the fitting for that tube from the engine block and briefly start the outboard. Anything trapped in there (that you're likely just shoving down with the trimmer string) will be almost instantly ejected by the force of the stream. It gets everything wet but if you submerge the outboard in a trashcan of fresh water it won't hurry anything and reliably clears that passage. That is....until the next time. All small outboards will eventually need this little operation from time to time. Or...you can keep using the fairly ineffective string trimmer line over and over and over.
Warning!...
...before removing the lower cover study the routing of that little tube VERY carefully. If not reinstalled in the correct way. It can be pinched when you reinstall the cover.
That little tube is supposed to be soft and flexible. If it isn't, it will catch small debris and plug too. It can drive you mad.
I replace that tube every 3 or four seasons on mine for that reason.
Good luck.
THANK YOU for the reply! The top of the engine is back to 95%, and I'm moving again.

The only remaining issue (other than excess bubbles from the lower holes above the prop) is that on one out of ten trips to or from the dock, the engine won't start without a lot of pulls while playing with the choke.

I'm going to save your reply and sometime next week run through everything one more time.
 

jgmo

Silver Medal Contributor
Hi,
Glad to hear you're making progress.
That accelerator pump nozzle and passage being clean and clear is so very important to all round performance. A partial clog CAN effect starting as well as idle AND top end. I can't emphasize that enough.

For your intermittent starting complaint here's a couple more ideas as well.....

... If you take the carb back off again, make certain that the bottom of your carb bowl is completely clean. There are passages at the bottom that sometimes need to be cleared of "mud" with a small piece of wire.

The cold start "enrichment" system on these is NOT a conventional butterfly type choke but, rather, a small pellet valve at the end of the "choke cable".

Those so called "chokes" can be problematic.

The cable, with pellet valve and rubber guide, is mounted to a plastic housing that threads into the carb body.

The threads on that housing are plastic and somewhat delicate. They can be easily stripped if overtightened.

They can also become loose and cause erratic "choke" function.

Upon close inspection, make certain also that the curved rubber boot that the choke cable is inserted in is not cracked or torn. If it is, you may need to replace the entire assembly to restore proper cold starting enrichment function.

Observe that rubber boot while working the cable in and out. If you detect the cable "bunching up" or arching as you push the cable to the "off" position, that indicates that the pellet valve isn't being fully pushed down to shut off the "extra fuel".

When that happens, you will experience hard starting when the engine is warm and reduced performance and fuel economy.

Hope this helps.

Good luck.
 
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