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Early 80's Evinrude 9.9 hp fuel issue

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budguyal

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I have an early 1980 Evinrude 9.9 hp that ran perfectly and then developed some performance issues early this year, here is a rough timeline of it's performance decline and the maintenance repairs completed in an attempt to resolve the issue but has not.

Starting well and running good for the first half hour of a trip then the motor started to bog down and run half speed.
Changes the spark plugs, rebuilt the carb, appeared like maybe it was starving for fuel and the float was stuck. I also replaced the hose and hand pump and connections from the fuel tank to the motor.

Next trip the motor started well and ran good but the same thing began to happen and about a half hour into the trip the motor lost half power, motor started bogging down but still running good enough to get to my destination.

Changed fuel pump , cleaned and checked carb again, motor started but began to have problems starting and running until eventually it wouldn't start and stay running.

I walked into my garage one day and was overpowered by the gas fumes, I thought i left the cap of a gas container for fuel that i had stored for the lawnmower but it turned out to be a puddle of gas under the lower unit of this 9.9, something I haven't seen before in the 2 years that I owned this boat. All symptoms pointed to a bad fuel pump or bad fuel line or hose leaking but I checked all and replaced most hoses and the fuel pump but when I leave the fuel line hooked up to the gas tank and motor, the gas is bypassing everything and leaking out through the lower unit somehow ????

I took it to a guy who was supposedly expeienced with Evinrude motors and after explaining the issues and everyting I already did he also rebuilt the carb and replaced the fuel pump ( same stuff i did) and the guy was scratching his head the same as i was about the gas running out of the lower unit and was never able to resolve the issue, he admitted defeat and of course didn't charge me anything for his time or parts replaced which I respect and kinda felt bad for him but on the other hand he didn't do anything different than I did so that's on him.

Does anyone else out there have any other ideas on what the problem might be before I end up just calling it all bad and replacing the unit? Thanks for any ideas or suggestions you may have. Feel free to ask for more information I would appreciate any help.

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Only reasons that fuel " pours " out is a hole in the fuel pump diaphragm or a bad float / float valve in the carburetor.----Be an easy fix here on my work bench.
 
racerone said:
Only reasons that fuel " pours " out is a hole in the fuel pump diaphragm or a bad float / float valve in the carburetor.----Be an easy fix here on my work bench.
Click to expand...
I'm scratching my head on this one, I replaced the fuel pump , it didn't help, I tore the carb down and rebuilt it and replaced the float and it didn't help. After all that I took it to a guy who has a small boat repair business, even after I told him what I did he sort of repeated the same steps which I guess I was ok with because maybe I did something wrong, he replaced the fuel pump, and tore the carb down and cleaned it up and adjusted the float and it didn't fix the problem, he had my boat for about 3 months before he finally gave up, he said he wasn't going to charge me anything since he felt bad he didn't fix the problem so I can't really complain but I'm still withut the use of my 9.9 Evinrude

After all that being said what are your thoughts?
 
Remove fuel pump.----Block off the fuel pump pressure pulse hole.-----Feed engine from a fuel tank above the motor.-----Test run.------Of test with another carburetor.-----So easy in my opinion.----Or perhaps the lower crankshaft seal is KAPOT??
 
racerone said:
Remove fuel pump.----Block off the fuel pump pressure pulse hole.-----Feed engine from a fuel tank above the motor.-----Test run.------Of test with another carburetor.-----So easy in my opinion.----Or perhaps the lower crankshaft seal is KAPOT??
Click to expand...
I'll give it a try and let you know, thanks for the insight. !
 
Have you done a spark test and cylinder drop test to confirm that both cylinders are firing? Are you sure the puddle under your lower unit is gas and not unburnt fuel dripping down from the exhaust? If one of your cylinders is not firing you will get 1/2 power, bogging down and of course a lot of unburnt fuel in the exhaust that will want to drip somewhere.

It's worth a check.
 
optsyeagle said:
Have you done a spark test and cylinder drop test to confirm that both cylinders are firing? Are you sure the puddle under your lower unit is gas and not unburnt fuel dripping down from the exhaust? If one of your cylinders is not firing you will get 1/2 power, bogging down and of course a lot of unburnt fuel in the exhaust that will want to drip somewhere.

It's worth a check.
Click to expand...
Thanks for the advice. The gas dripping out of the lower unit does it when it's not running, one afternoon when it got hot in my garage the pressure in the tank rose and forced the fuel out , when I walked into my garage and was overwhelmed with the smell of gas and thought I might of had a gas can for my lawnmower leak but there was a puddle under my lower unit. I disconnected the gas hose from the tank and relieved the tank pressure . I do have spark out of both cylinders and I also did a compression check, both cylinders had compression on the low side but still good
 
If you have an OEM tank (steel or plastic) connecting the fuel line to the tank opens the tank vent. Look for a short pin maybe 1/8" long that gets depressed in then hooking up the connection to the tank. That opens the vent built into the tank connector/fuel gauge assembly.
If it is building pressure, then the vent isn't functioning. Start by figuring out why.
 
budguyal said:
I have an early 1980 Evinrude 9.9 hp that ran perfectly and then developed some performance issues early this year, here is a rough timeline of it's performance decline and the maintenance repairs completed in an attempt to resolve the issue but has not.

Starting well and running good for the first half hour of a trip then the motor started to bog down and run half speed.
Changes the spark plugs, rebuilt the carb, appeared like maybe it was starving for fuel and the float was stuck. I also replaced the hose and hand pump and connections from the fuel tank to the motor.

Next trip the motor started well and ran good but the same thing began to happen and about a half hour into the trip the motor lost half power, motor started bogging down but still running good enough to get to my destination.

Changed fuel pump , cleaned and checked carb again, motor started but began to have problems starting and running until eventually it wouldn't start and stay running.

I walked into my garage one day and was overpowered by the gas fumes, I thought i left the cap of a gas container for fuel that i had stored for the lawnmower but it turned out to be a puddle of gas under the lower unit of this 9.9, something I haven't seen before in the 2 years that I owned this boat. All symptoms pointed to a bad fuel pump or bad fuel line or hose leaking but I checked all and replaced most hoses and the fuel pump but when I leave the fuel line hooked up to the gas tank and motor, the gas is bypassing everything and leaking out through the lower unit somehow ????

I took it to a guy who was supposedly expeienced with Evinrude motors and after explaining the issues and everyting I already did he also rebuilt the carb and replaced the fuel pump ( same stuff i did) and the guy was scratching his head the same as i was about the gas running out of the lower unit and was never able to resolve the issue, he admitted defeat and of course didn't charge me anything for his time or parts replaced which I respect and kinda felt bad for him but on the other hand he didn't do anything different than I did so that's on him.

Does anyone else out there have any other ideas on what the problem might be before I end up just calling it all bad and replacing the unit? Thanks for any ideas or suggestions you may have. Feel free to ask for more information I would appreciate any help.
There might be an issue with the fuel line or carburetor overflow, or even the fuel needle and seat sticking. Given the fuel bypassing through the lower unit, you could have a problem with the crankcase seals or carburetor flooding. Consider inspecting the lower unit for leaks or checking the reed valves. Writing a narrative essay requires creativity and a clear storytelling approach, but I found myself struggling. That’s when I discovered https://academized.com/buy-narrative-essay and they exceeded my expectations. The essay was engaging, personal, and perfectly structured, bringing my story to life. The writer paid attention to every detail and followed my instructions meticulously. The work was delivered before the deadline, giving me ample time to review it. I highly recommend their service to anyone needing help with narrative essays.
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Can I ask something? If you don't mind.
 
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