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Honda 9.9 Overheating problem

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perryrlund

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I have a 9.9 Honda that is 7 years old. Never a problem with it. Had it out a couple times this spring. Yesterday took it out and it ran for about 30 seconds and shut down. Restarted and same thing. Looked and no water discharge from the water pump hose. At home took side plate off. You have two hoses that go through the side plate for discharge. You have the black rubber one which is the main discharge from the water pump. This is where the water pees out when running. This hose was clear. The other one is a clear plastic one that come off the upper part of the motor. This one was plugged with some gunk. You could not blow through it. Took this hose off and cleaned it out. Problem fixed, I assumed. Took the boat down to the lake and started it and it was peeing out water as it should. Ran it for about 3 minutes and started to sputter and stopped peeing out water again. Looked at both of the hoses and no problems there. This, I thought, is an impeller/water pump problem. Took the intake screen off and as clean is the day it was new. Definitely thinking it's now a bad impeller in the water pump. Took the lower unit off and the impeller is in perfect condition. Will put a new impeller kit in as long as I have it apart.

The only two other explanations would be a thermostat issue or a blockage somewhere in the circulation in the cooling system itself. The motor is ver clean and no debris at all when I took off the intake screen and no debris in the impeller housing, it's as clean as the day it was new.

Any thoughts on this? I will replace the thermostat but prior to doing that I was wondering if any one else has any thoughts. I'm assuming if the thermostat is not working properly and the engine begins to overheat the engine shuts itself down.

Last question, you have the rubber black hose that discharges the water from the cooling system out the side panel. This is the peeing stream. Then right next to it you have the clear plastic line that attaches to a nipple on the top side of the motor. What is the purpose of the clear plastic line that comes out the nipple? Is it some type of water discharge line from the top of the motor or is it some type of line that would flush any water from the carb? Being that it is clear, I'm thinking it might be gas related and not water related.

Any help from the Honda experts would be appreciated.
 
Hi perrylund,

Welcome to the forum.
First of all, I think you are wise making the decision to replace the pump impeller and the thermostat. 7 years is a long time for both of those even if they do still look good.
Sounds like you boat in some very clean water or do really good flushes or both.

Question: does your green oil pressure lamp come on and remain on when the engine is running? If not, that might be a concern.

These engines do have programmed engine protection designed to derate the power when overheating or if the oil pressure is too low. But it's supposed to happen in stages ie: you lose power slowly before any shut down.

That's supposed to give you time to "limp" out of a busy seaway or corridor and find a safe moorage.

Shutting down suddenly like you describe after only a few seconds of running could, as you have already said, indicate a fueling problem.

Anything is possible though so it's not good to assume anything when trying to figure this out.

If you still have it together and can run it, you might want to try making a couple of basic checks.

First, ensure that your fuel line connector is on securely and latched.

This "symptom" sounds suspiciously like a vacuum is occurring in the fuel tank. Make sure that the tank is properly venting and that the vent screw is fully open. If it keeps stalling you can test for this by running with the fuel tank cap very loose or off to see what happens. Just guard against spilling any gas if you try that!

When it stalls, check the primer bulb to see if it's firm and hasn't gone soft. And, if you can react fast enough try squeezing the bulb to see if you can keep it running by doing that.

Another question: Is it now peeing out the water tell-tale after you cleared the black tube? If not, we can discuss how to solve that problem.

The clear tube going to the other discharge nozzle on the side cover is connected to the bottom of the carburetor float chamber. It simply allows you to be able to drain the carb bowl into a container for inspection. It should have nothing to do with this issue.
 
Green oil light is on as it should be and oil is good, oil and filter just changed. You mention the vent cap on the tank. Even if that were an issue should it still not be discharging water while it is running? I never changed anything on the fuel tank and I cleaned the tank out two weeks ago when I took it out for the spring and filled up the tank with the same high grade gas as alway.

The black rubber hose was not clogged it was the clear one from the carb that was clogged. Could this have created a vacuum problem?

The plastic fuel tank is 7 years old and is showing age and has some cracks in the plastic. It still works properly but I have a new one ordered and will replace it in the next week or so as well then I'll take it down to the lake and test everything out and see where I'm at. The baffling part was no water discharge at all but when I unplugged the clear rubber line, it started right up and ran fine for about 3 minutes discharging water like it should then the stream got less and the motor stopped. I think you're on to something with the vacuum issue. Thanks for all the advice, It'll take me a day or two to get the parts but I'll follow your suggestions and post to the site. Thanks again.
 
You're right. It should have been peeing water while running.

Sorry, I missed "it ran 3 minutes" before. I only thought it shut down after 30 seconds.

But, yes, 3 minutes shut down while seeing the pee stream slowly falling off would indicate a pump issue is more likely.

The gas drain tube being plugged would have no bearing on how the outboard runs. It won't create a vacuum.
If the carb drain screw is tight then it should make no difference and if the drain screw is loose, you should have a gas leak.
Any idea how that tube got clogged? If it's connected at both ends, nothing can get in it unless the carb drain is opened.
I do suggest that you open the drain screw though and catch the gas in a clear container to see what's in there. It's just part of routine maintenance.

Take care not to "booger" up the slot of that brass screw. They are tight and require a nicely fitting, long screwdriver to open and close.

Good luck.
 
My pee tube (yes the black one) was actually more dribbling rather than squirting and I found the hose was kinked just below the plate it go thru after it comes out the engine. You DO need to take the side cover off to see the hose run correctly. If that is 100%clear right to the motor then you can look at the cooling system .. OK quick question ..Does the 9.9 have a flush thread hole right next to the themostat housing plate ..it it does I use a garden hose to flush the upper head system and water into the flush fitting should come out strongly via the pee tube WARNING ..you do this with the motor NOT running as it's a static flush ... I also took out my thermostat and cleaning it up as well as the housing it sits in ..if water flows thru the flush fitting (Honda sell them IF your motor has one) then do as JGMO suggests and change the impellor!! He is HIGHLY qualified on most aspects of small Honda motors and saved me many hours of frustration!!
 
From a 2014 9.9hp owners manual
IMG_6996.jpeg
 
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