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Engine Stalls when idle

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LE36

New member
I am new to a 1995 Mercruiser 5.0L that stalls when idle.
I am not mechanically inclined and limited to marine repair service providers.
I had convinced myself that the problem was/is the IAC valve.
I was informed this engine does not have such. So, I asked if there is an equivalent.
So here goes:
Any thoughts on why this engine stalls when idle (engine is relatively well maintained)?

Thanks for any ideas,

LE36
 
If it has a carb, there's no IAC- that's only for fuel injected engines.

If it ran OK before, it should run now. How old is the gas and does it have Ethanol in it? If the latter and especially if it's old, take a fuel sample, let it sit for awhile and look for particulates, milky appearance or water droplets. If it has any/all of those, you'll need to remove that stuff. If you can borrow a fuel tank from an outboard, run it on that and if it does better, look into the fuel line, tank, fuel, etc.

Don't mess with mixture/idle screws if it ran OK before.

Look at the flame arrestor- if it's filthy, clean it. To confirm its effect on the way the emgine runs, remove the arrestor- if it runs, clean it. This is probably the most-neglected item I have seen on the (literally) many hundreds of boats I worked on.

When I was trained for Mastercraft boats, they told us to get a bottle with a small nozzle, like from Mustard, Ketchup, etc and put some gas in it. If an engine wouldn't run without squirting gas into the carb, it has a fuel problem. If it bogs and stops, it's likely rich and if it comes to life, it's likely lean but there's always an underlying reason for either. If you want to avoid problems with backfiring, squirt the gas into the flame arrestor- it won't need much to cause it to run better or worse. You can also loosen the nut holding the flame arrestor and drizzle it onto the hole for the stud- the vacuum will pull the gas in.
 
Thank you for the "pearls" jimn.
*I am not mechanically inclined.
There was some fuel left from Aug 2023 (20gal - 30gal) in a 50 gallon tank
I have taken the boat out the past 3 weekend
I have used and added about 50 gallons of 91 octane in this time. All this information because I am not sure what ethanol is exactly.
LE36
 
LE36 said:
Thank you for the "pearls" jimn.
*I am not mechanically inclined.
There was some fuel left from Aug 2023 (20gal - 30gal) in a 50 gallon tank
I have taken the boat out the past 3 weekend
I have used and added about 50 gallons of 91 octane in this time. All this information because I am not sure what ethanol is exactly.
LE36
Click to expand...
Where are you located?

Ethanol is a type of alcohol, added to increase Octane and burn cleaner but it causes problems by mixing with moisture in the air that enters the tank through the vent on the hull. Any other comments about why it's there will be reserved because they would probably result in me being suspended or booted from the forum.
 
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