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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 14477
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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I have a 1989 johnson vro 70 hp over heating problem occurring

Customer Question

I have a 1989 johnson vro 70 hp over heating problem occurring 1/2 to 1 hour of operation at low to moderator speeds with buzzer going off and the motor idling down and shutting down eventually. I can let cool and restart only to have same happen again. I have replaced a perfectly good water pump, buzzer sensor, and thermostat all with same results. The engine block never seems hot to the touch and there is a full stream of water exiting with restrictive nosel removed. Possible questions might be is this an oil sensing problem or are the carburetors running too lean?
Submitted: 1 year ago.
Category: Boat
Expert:  Jason replied 1 year ago.
Hello my name is ***** ***** am I speaking with? You said it had an overheating problem, but that the engine is actually cool. Are you overheating, or are you just getting an alarm that you are trying to figure out?
Customer: replied 1 year ago.
I unplugged the alarm
Expert:  Jason replied 1 year ago.
I don't understand your question as you wrote it. What is it you are trying to figure out?
Customer: replied 1 year ago.
Why does the motor keep shutting down?
Expert:  Jason replied 1 year ago.
Is the engine stalling, or going into a power reduction?
Customer: replied 1 year ago.
These motors are preset to go into idle when over heating
Expert:  Jason replied 1 year ago.
So is that what your engine is doing? Is it going to idle, or is it stalling?
Customer: replied 1 year ago.
Both Idle then shut down
Expert:  Jason replied 1 year ago.
When it stalls have you checked for spark?
Customer: replied 1 year ago.
only after 15 to 20 minutes and trying to restart sucessfully
Expert:  Jason replied 1 year ago.
What needs to happen is you would have to check for spark with an adjustable gap spark tester as soon as it stalls. And see if you have it on any cylinder. No cylinders. And to also see what the spark intensity is. That is step one. Do you think you can do that?
Customer: replied 1 year ago.
I do not have gap spark tester but all 3 plugs are new and gaped .030
Expert:  Jason replied 1 year ago.
If you are looking to do this yourself you would need the tools. Otherwise it can not be done. There would be many tools required depending on how the testing goes. Do you have a decent quality volt/ohm meter. And do you know how to take electrical resistance measurements?
Customer: replied 1 year ago.
Sorry, I do not have the tools nor the electrical experience, again my best guess was to adjust the carburetors richer or off to the $100/hr mechnaics!
Expert:  Jason replied 1 year ago.
To be honest it sounds like you have an ignition problem, and not a fuel problem. Aside from that the fuel jets inside of the carbs are fixed jets, not adjsutable jets. So there isn't really a way to adjust them.
Customer: replied 1 year ago.
It looks like we are done with any kind of mechanical fix in my wheelhouse and my frustration with other mechanics misdirection for my problem. I thank you for you attempt and I will get back to you when I get solution so as you won't lose any sleep. happy sailing!
Expert:  Jason replied 1 year ago.
In order to help narrow you down a little bit. Go and duplicate the problem. When it won't start. Pop the engine cover off and disconnect the black/yellow wire from the powerpack. This will take the keyswitch and kill switch out of the loop. If it now starts, you have either a bad key switch, or kill switch. If it will not start, the problem is on the engine. And the 2 most likely suspects here are a bad powerpack, or a bad stator. The other issue on these engines is they are also known for cracking flywheel magnets. When that happens they can wipe out the stator, causing it to go bad. So as you get into this, if it looks like you have a bad stator. Carefully inspect the flywheel as well. There are never any time limits here so if you want to get back to me later on that is no problems. Good luck!Jason

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