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Charles
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3342
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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2005 mercury 250 four stroke Engine will run full throttle

Customer Question

2005 mercury 250 four stroke
Engine will run full throttle fine, idle fine for half hour or more, Then start running rough and stall. Will restart after a little while and start cycle over again. Changed both gas filters and still doing it. Any suggestions?
Submitted: 1 year ago.
Category: Boat
Expert:  Charles replied 1 year ago.

Hello, my name is***** will assist you today.

Would you please post the serial number of the engine?

Customer: replied 1 year ago.
I don't think I have serial number on hand. It's verado
Expert:  Charles replied 1 year ago.

Ok, that works.

Is there a primer bulb in the fuel line?

How is the oil and the oil level, does it rise at all?

Are you getting any alarms?

Customer: replied 1 year ago.
We traced the line and couldn't find a bulb. Oil level is good. No alarms. We went an hour full throttle no problems. But happens mostly when trolling. We tried new gas same problems.
Expert:  Charles replied 1 year ago.

Do you have SmartCraft gauges?

When was the last time that the cooling system was serviced?

Customer: replied 1 year ago.
We went out the first four times this year no problems. We went 8 hours at a time. Fifth time we went out drove 20 miles no problem full throttle trolled for four hours the all of a sudden started shaking and stalled once.
Customer: replied 1 year ago.
We plan on going tomorrow morning and trying what you recommend.
Expert:  Charles replied 1 year ago.

Ok,

Is the boat on a trailer? Yu will need to have access to the entire engine.

Has any work been done to the fuel system on the engine at all?

Customer: replied 1 year ago.
Boat was just purchased this year from a reputable shop. It's a 2005 engine on a 2008 boat. No work done to the fuel system that I know of. When we bought the boat it had 200 gallons we were down to 100 when it first happened. We put in 40 new gallons of fuel and additive and changed both filters. Not on a trailer but can put it on a trailer.
Expert:  Charles replied 1 year ago.

Ok,

I have a few ideas on what is going on here. You either have a failed hose inside the FSM or the fuel pick up is cracked and sucking air. You will need several tools to check items that need to be checked.

Customer: replied 1 year ago.
We plan on being at the boat tomorrow in 12 hours. can I continue to message you at that time through this service?
Expert:  Charles replied 1 year ago.

Yes we can continue then. I will be online around 10 AM CST.

Customer: replied 1 year ago.
Ok we will try the few things you recommended. What tools would you suggest we bring?
Expert:  Charles replied 1 year ago.

8, 10, and 13mm sockets a 5/16" nutdriver. Pliers to remove a hose. A 9/16" wrench, a 3/4" wrench and a 1/4" nut driver.

The boat will need to be on the trailer.

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