Logo
FULL SITE MENU

BF 9.9 Dies soon after starting

R

RPL

New member
Hoping someone can helps me out with this problem.
Motor starts right up, no problem at idle but under load it will run for a few minutes then die slowly over a few seconds.
It will start right up again and repeat the same thing with out priming so I believe that rules out fuel, bulb always is stiff and priming will not keep it from dying. Oil pressure light is always on,
The tell tale has a stream and when I run it with the thermostat pulled and the cover open there is flow just not sure if it’s enough if this is an overheating issue possibly impeller?
Motor is a pain to remove from the rib so I would like to be somewhat sure of possible causes
 
If it runs and dies slowly while running, it sounds like a fuel issue- carb clogged or bad/old fuel? Is this outboard used infrequently?

Not sure how the overheating alarm works on these small outboards- maybe someone else can give you advice on that possibility.
 
You don't list year or if it's an A or D model. That might help.

If it's a D model, does it have a manual or auto choke?

But FIRST thing to check for this is the fuel tank vent. If it's not open all the way or is partially clogged, this is the classic symptom.

If you're not sure about if it's clear or not, try running with the fuel tank cap loose. But be very cautious doing that as splling gas can catch your boat on fire!

Try that "trick" only on glass calm, flat water with no other boats around to make waves. Make very slow, shallow turns to prevent spilling.

Having a fire extinguisher handy is recommended.

Good luck.
 
It is a BF 9.9D with a manual choke . I have run it with the tank cap loosened and the same thing happened.
The reason I dont think it's fuel related is that it fires right up again after it cuts out, the primer bulb is always stiff and it won't recover as it's dying if I try to pump the primer bulb.
There is no alarm, it just looses power and rpm for about 10 sec before it does die and will fire right back up without me doing anything and will again run nicely for another minute before cutting out again.
I have read that a partially damaged impeller with reduce flow enough to cause engine to shut down with an overheat.
 
It has to run long enough to get hot in order to shut down from an overheat, is this happening at a cold start?

If it’s happening after it’s run a few minutes, it could be a blockage in the cooling system.

It may be getting enough fuel flow to idle but not enough when it needs more as rpm goes up.
 
From a cold start, after it warms up for a few minutes, it will run for 2 or 3 minutes under load before it cuts out, it seems like once it's warmed up the time it will run for gets shorter and shorter, but always fires right back up without me doing anything
How to best check for blockage?
 
www.selffixer.com

Honda Outboard Manuals PDF | Download Online

Download official Honda outboard service manuals. From High Quality digital PDFs to rare vintage guides, get the repair data you need. Instant access. Manuals List in PDF
www.selffixer.com www.selffixer.com

Perhaps you can find a service manual from the above link. Even if you can’t find your exact year it will give you some troubleshooting ideas for various scenarios.

Your description “There is no alarm, it just looses power and rpm for about 10 sec before it does die and will fire right back up without me doing anything and will again run nicely for another minute before cutting out again.” leads me to suspect it’s a fuel starvation issue. Overheating, one would think the engine would slowly slow itself down to idle but not shut itself down(stall). Electrical issues is usually a sudden stop, like a switch was turned off. I could be totally off base on my thoughts, I’m fairly new to Honda engines.
 
Thanks for the link, Manuals are very reasonably priced
So if it is fuel related and basically running out of fuel, would I not have to reprime using the primer bulb? This is not the case, primer bulb is always stiff. Motor starts right up after the shut down and sounds good for the next minute until it shuts down again
 
See Post #2. Bad/old fuel? Water in the fuel? I know with my ATV (Honda) old fuel will act like you’re describing. Starts and idles good, put it into gear and try moving it falls flat on its face.

I don’t think the tiller model has an overheating alarm, only low oil pressure. To confirm overheating all I can think of would be to use an infrared temperature “gun” and monitor the engine as it warms up. I don’t know what the operating temperature should be but someone on this forum will know.

“So if it is fuel related and basically running out of fuel, would I not have to reprime using the primer bulb?“ One would think so. What if the carb isn’t getting enough air or too much air would that not throw off the air to fuel mixture off and cause running issues?
 
Thanks for the responses.
I do have an IR gun so will try that tomorrow when I'm at the boat. I just picked up an impeller kit and it's due for replacement so that's first on the list.
This motor was run in salt water by the previous owner so I'm looking at doing a flush with some barnacle buster solution I have if the impeller doesn't do the trick.
The motor runs great for the first 2 or 3 minutes under load until it dies and this situation will repeat over and over
 
Only the remote equipped 9.9D outboards have the buzzer I believe.

You might try running it BRIEFLY with the wire for the temperature sensor disconnected to see if anything changes. DON'T FORGET to put it back. That sensor is the engines lifesaver.

The impeller should easily last longer than 2 years UNLESS a new impeller was installed in a worn liner (cup) or a damaged housing that allows the liner to move around. Also "dry starts"...starting the engine while it's trimmed up... will damage the pump quickly. It needs water to lube itself.

If it's not overheating, a couple of other things might cause this.

#1: The choke cable and it's housing assembly is worn and the choke is "walking out" making the mixture too rich. Check that when you push the choke in all the way, it stays put and doesn't "come on" by itself. It should push in all the way and stay there with no "spring back" when you release it.

These carbs are tricky, have certain little quirks, are easy to get clogged by dirty fuel and can be very difficult to get completely clean. Especially true for the "uninitiated". A long time automotive carb rebuilder myself, I struggled to figure them out at first. I still consult the Honda Marine Carburetion Manual for cleaning these little puppies

They have an accelerator pump that's poorly designed but the delivery side of the pump circuit is VERY critical as to how the engine runs. If the TINY spray nozzle on the accelerator pump brass tube gets plugged or that tube gets clogged, it will affect the engine in some unpredictable running and might even cause hard or no starting.

You say it fires right up but that doesn't mean the tube or nozzle isn't partially blocked. They are a PAIN sometimes.

Even something as simple as a plugged bowl vent might cause something like this. They require atmospheric pressure inside the float bowl to help fuel to flow.

While I don't remember seeing this exact symptom before, if you can't find another reason for this your carb might just need cleaning.

Good luck.
 
I thought I found something as a few of the impeller fins were not facing the correct way. I replaced the impeller but the same problem happened.
I measure temp with an Ir gun beside both plugs, lower was 26deg C, upper was 60 deg so looks like there's a blockage.
The procedure I read for a clean/flush was to remove lower leg and pump solution like barnacle buster up thru water tube and circulate with engine off then flush with fresh water?

Video of engine dying after 3 minutes under load

 
Are the 23°C lower and 60°C upper temperature readings being seen as the engine rpm drops?

It does appear that it might be going into "limp" or "guardian" mode but your temperature testing would not seem to actually support that conclusion.

23°C (74°f) is very low and 60°C (140°f) is near normal operating temperature and neither would (or shouldn't) be cause to have the Engine Protection program in the CDI to be triggered.

Unless, during your test, you see the temp difference, assume a blockage (correctly I would think) and just stop measuring. Is that the case?

The system can't see the difference in temperature so that's not the reason either.

The video has a "clacking" or clicking noise. Is that something that started happening along with the rpm loss?

At any rate, you're probably going to need to get the outboard ashore to proceed with trying to deal with that temperature difference.
 
Are the 23°C lower and 60°C upper temperature readings being seen as the engine rpm drops?

What I measured was 23 lower cylinder and 60 upper temperature right next to the plugs just after it shut down, I will have to repeat this test as the room temperature statement is correct.
Not sure about a clacking noise, this engine is new to me so not sure how it should sound, there is some water cavitation noise about half way through but no other noises that I'm aware of.
I will have to put a timing light on it to confirm spark on both cylinders
 
Ok. Timing light is a good idea.

I would be interested in seeing a temp reading of the cylinder head adjacent/near the water temperature sensor. Item 16 in the link below.


NSDON's suggestion about it maybe running on one cylinder might be correct. The Honda twins of this model series are very well balanced and will run pretty smoothly on only one hole like that but usually only when in neutral. They have fooled me before.

If you don't measure high temperature there (80°C +) try unplugging that sensor and test again
 
Back
Top