Home › Forum › Ask A Member › 57 Johnson 7 1/2 Starts but won’t run
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JohnRude.
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April 18, 2023 at 5:22 am #275261
When you say that the carb bowl is full when it dies, how do you know that, for sure? If you mean the clear filter bowl (that Frank mentioned) is still full, that doesn’t necessarily mean the whole bowl is still full. Here is another question: Will it stay running if you keep pumping the primer button on the tank?
You could try taking out the filter and see if it will stay going, like Frank said. That is certainly easier than going right after the rubber check valves; although it’s not as easy to remove and install that filter, as you might think. On my 7.5 Evinrude (same motor) it’s easier for me to take the whole carb off, or the front lower cowl off, than it is to remove and reinstall that filter, with the carb on. And, since you may have to take the carb off, it’s not much further to the rubber check valves. You just take out the screws holding the intake manifold and reed plate on, remove the manifold and plate, and you’ll see the valves. I can’t guarantee this, but a lot of times, the gaskets for those items come away intact and reusable.
Long live American manufacturing!
April 18, 2023 at 11:03 am #275269A couple of years ago I had an OMC motor that would not push fuel from the tank. Like has been mentioned earlier in this thread….the valve behind the reed plate can cause that. I imagine that as that little piece of rubber gets older and older…..we will see more issues with them failing.
Another member here who has a pressure gauge tells me that the pressure in the fuel line from the tank to the carb varies from motor to motor….and the condition of that little rubber valve has a lot to do with it.
April 19, 2023 at 4:53 pm #275311Yes, I did a complete carb rebuild and made sure all orifices were clean and clear, new packing, etc. You pegged it (again) with raising the tank above the motor. I thought I’d try that first. Started and ran. Idled pretty good after a bit. When it started running rough again I pumped the tank up and it smoothed out again. Certainly sounds like the check valves are worn.
However, while it was running and pumping water I noticed water leaking out around the shift lever AND it wouldn’t go into gear. The handle feels like it is engaging but nothing happens. I was leaving the lower end until I made sure the motor was up to snuff.
April 19, 2023 at 5:06 pm #275312Check for a broken shear pin.
Most of those motors will drip water from the shifter shaft. There is an o-ring that you can replace when you have the powerhead off.
April 19, 2023 at 6:20 pm #275314Yes, the whole clear sediment bowl was full and yes when I raised the tank above the motor it continued to run much longer. When it started to act up I pumped up the tank some more and the motor went back to running smooth.
April 19, 2023 at 7:41 pm #275317glad gravity feeding helped. now that you do have it running for 3-4 minutes open the tank cap… it should be pressurized. if it is !!!! something screwy in the tank not pushing fuel up the carb
if not ……spray soapy water from tank to air nipple.. if no bubbles then the flapper valve needs a look at or the nipple is crudded shut . poke a piece of wire or blast with carb cleaner
if you need a flapper I can dig one up probably but needs digging in the bin box. 🙂
Joining AOMCI has priviledges 🙂
April 20, 2023 at 8:53 am #275341How does a rookie send a PM?
April 20, 2023 at 9:03 am #275342click on the “target” member name
clik on private message box…
fill and send 🙂
Joining AOMCI has priviledges 🙂
April 20, 2023 at 9:12 am #275343OK. thanks. Will do Kimosabe.
I will start with running the tanks on a motor that I know (hope) works. I presume that the fuel mix is 16:1 for the 7.5.
April 20, 2023 at 9:13 am #275344If the tanks shake out OK, then I’ll pull the leaf plate and replace the check valves.
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