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boat runs perfect for 10 minutes then acts like its running

 
Tan Partin's Avatar
  • Answered by:Tan Partin
  • Mercruiser Certifi Technician
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Customer Question

boat runs perfect for 10 minutes then acts like its running out of gas, turn the motor off and restart then runs fine for another 10 minutes, over and over

 

Optional Information:
Make (of engine): merc cruser, gm
Model (of engine): 5.0
Year: 2005

Already Tried:
new distributor cap

Submitted: 281 days ago.
Category: Boat
Value: $28
Status: CLOSED
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Expert:  Tan Partin replied 281 days ago.

Hi my name isXXXXX will assist you.

.

This sounds like a case of fuel starvation due to debris in the fuel tank of boat side fuel system. Run the engine on another fuel source if the engine runs better you know that the cause of the issue is fuel starvation of the boat side fuel system. If no change then the engine is the issue and will require further trouble shooting. Post back with questions.

Customer replied 281 days ago.

Relist: Answer quality.

Customer replied 281 days ago.

fuel system is like new, brand new filter installed, no evidence of debris, i think fuel pump relay, if such a thing maybe a throttle body?, fuel pump, computer?

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Expert:  Tan Partin replied 280 days and 23 hours ago.

The engine running for 10 minuted then dieing and restarting again to do it all over again is not electrical. A relay won't quit then miraculously cure it self to quit again in 10 minutes. If there is no debris as you claim then the throttle body won't be clogged. The symptoms are debris in the fuel tank getting sucked up to the pick up tube screen till fuel flow is shut off killing the engine. When the engine dies the fuel vacuum quits and the debris is released from the pick up tube. The you run the boat again and the tube takes 10 minutes to collect enough debris to clog the tube causing fuel starvation. Repeating the cycle again. Now have you run the engine on another fuel source to eliminate it as a cause for your issue? Is it possible that I might be right since I am the expert you are asking? If the debris can't get past the screen on the end of the pick up tube it can't get to the filter. I have seen brand new boats with carpet fibers in the tank clog the screen on the end of the pick up tube. And the customer swore I was nuts he was eating crow when I pulled the debris from the fuel tank. So there is a good chance I do know what I am talking about. Is it possible?

Customer replied 280 days and 23 hours ago.

i would love to beleive your right, but iam a a&p aircraft tech, the first, simplest and cheapest thing to check fuel contamination, right and left side!

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Expert:  Tan Partin replied 280 days and 23 hours ago.

You know how easy it is to run the engine on another fuel source? Get a jerry can stick a hose in the can connect to the fuel filter to the engine. Run the boat. Simple. What you mean by right and left I have no idea what you mean. Boat fuel systems are not aircraft. Boats sit allot collecting water then with the addition of ethanol to the fuel. If it sits for more than 3 months the ethanol and water separate forming a ball of sludge in the fuel tank rolling around. This is call phase separation. This causes more fuel related problems than you can imagine. Here is an article on the affects of ethanol.graphic

Customer replied 280 days and 23 hours ago.

if it was fuel stravation, when the motor starts to cut out, we have tried a shot of starting fluid in the intake that would have helped for a second or two and fyi never use gas with ethanol, expesially an out board and this perticular boat has a left tank aswell as a right tank 20 gal a side, thanks for your response i will mark as positive, just in case in turns out your right!!

Accepted Answer

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Expert:  Tan Partin replied 280 days and 23 hours ago.

Now you said outboard in you original post you said 5.0 Mercruiser sterndrive. Under a heavy load starting fluid wouldn't be enough to boost. The engine at full throttle will burn 30 gallons per hour. Check the anti siphon valves where the fuel line connects to the fuel tank. Check all the fuel lines, check the tank vents. These are all areas you can have a fuel restricytion as part of the boat side fuel system. Switching tanks you are still using the same fuel lines.Tan Partin41093.0765705671

Expert TypeMercruiser Certifi Technician
Category: Boat
Pos. Feedback: 99.3 %
Accepts: 6321
Answered: 7/3/2012

Experience: 35 yrs. experience. I/O, Outboard & Inboard, Complete engine repairs.Certified Technician

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Customer replied 280 days and 12 hours ago.

Tan, your arrogance most always will stop you from diagnosing the hard proplems, you an expert , my ass!!

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Expert:  Tan Partin replied 280 days and 12 hours ago.

I'm sorry I wasn't trying to be arrogant. I was just trying to help. You have to understand I deal with all kinds of people who always doubt my expertise. Many times they come across in a disrespectful way not believing what I am saying. Trouble shooting is a process of elimination so we have to eliminate to get to the problem. I have been working on boats for 35 years as a paid professional; and was considered one of the best in Jacksonville Fla. So if I don't meet you expectations I am sorry. All I ask you to do was to eliminate the boat side fuel system as a cause and you wanted to argue as that wasn't the problem. This would have told us if the engine was the problem or the boat side fuel system was the problem. Narrowing down the possible causes. I don't what that has to do with being arrogant. 9 times out of 10 boats have a fuel related issue. So I always start at the source of the fuel system which is the fuel tank. So tell me how that doesn't make sense and I will be glad to change.

Customer replied 276 days and 11 hours ago.

Tan, fyi the proplem with my boat turned out to be a sensor tip in the throttle body

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Expert:  Tan Partin replied 276 days and 11 hours ago.

Which sensor tip are you referring to? There are only 2 sensors in the throttle body. TPS(throttle position sensor) IAC (idle air control)

Customer replied 276 days and 10 hours ago.

Both, part #853678t

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Expert:  Tan Partin replied 276 days and 10 hours ago.

Thats the TPS which tells the computer where the throttle plate is. This would have shown up on the computer when checking for codes or faults. Thats an unusual type failure for a TPS to do it in a ten minutes. Usually an electrical component either works or it doesn't. These will fail at a certain rpms not at a certain time. But it is what it is glad you got the issue resolved. Sorry for the arrogance on my part. I wasn't trying to be that way.

Customer replied 275 days and 12 hours ago.

if I would of had a computer to check codes or faults, would of had no need to go online !

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Expert:  Tan Partin replied 275 days and 11 hours ago.

Ok, I see .

 
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