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Engine shuts itself down

Old 06-11-2018, 07:46 PM
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Default Engine shuts itself down

2005 Mercury Optimax 115hp 2 stroke runs fine at about 3/4 throttle, but if I open it up wide open it will run fine for 5 to 10 minutes then shut itself down. I can then restart and run it as long as I don't open it up full throttle. No warning sounds occur such as if I am low on oil or if my water pump isn't working. I have changed the spark plugs and the fuel filter. Any ideas?
Old 06-11-2018, 07:54 PM
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Sounds like a fuel problem,not enough fuel getting to the carbs.when it does die is the prime bulb soft or still hard.if it is soft then its a fuel problem and if it is hard you need to look elsewhere.
Old 06-11-2018, 08:05 PM
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Originally Posted by dogslife View Post
Sounds like a fuel problem,not enough fuel getting to the carbs.when it does die is the prime bulb soft or still hard.if it is soft then its a fuel problem and if it is hard you need to look elsewhere.
Haven't checked the bulb. Could it be the fuel pump? Will a fuel pump work fine except at full throttle? Seems like it would either work or not.
Old 06-11-2018, 09:38 PM
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Originally Posted by ascdds View Post
Haven't checked the bulb. Could it be the fuel pump? Will a fuel pump work fine except at full throttle? Seems like it would either work or not.
My engine did the same, it was a fuel vent I kept closed, causing rpms over 4000 steady to throw a warming. Could be a collapsing fuel line as well if old enough.
Old 06-12-2018, 06:40 AM
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Originally Posted by antlerz22 View Post


My engine did the same, it was a fuel vent I kept closed, causing rpms over 4000 steady to throw a warming. Could be a collapsing fuel line as well if old enough.
Yes it can be those also,must fuel tanks that I have seen dont have a vent that you can close off not saying yours does not.
I have seen some fuel pumps not pump enough to keep up with the high demand for higher rpms but can do fine at the lower rpms,thats why I said to check the prime bulb right after it shuts off from the higher rpm run.If the bulb is soft then have someone try to pump the bulb when it starts to act up while you or someone else drives the boat and if it keeps running at the higher rpm then I would say its the fuel pump not keeping up with the demand,if it still dies and the bulb does not get hard then you have a supply problem to the bulb like fuel line or a venting problem to the tank.
Good luck and let us know what you find so we can try and help.

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