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Michael, Master Mechanic
Category: Boat
Satisfied Customers: 257
Experience:  Over 25 years experience working on everything from PWC's to Mega Yachts
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I have a 200hp yamaha outboard o66 series the motor starts

Customer Question

i have a 200hp yamaha outboard o66 series the motor starts and idles fine when the boat planes out after a few minutes i lose fuel pressure the motor slows but does not die then reeves up again then slows again i changed water separater and motor filter i also used a mobile fuel tank same results
Submitted: 2 years ago.
Category: Boat
Customer: replied 2 years ago.
i logged in yesterday no response
Customer: replied 2 years ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Michael replied 2 years ago.
Hello, My name is Michael... I have had the same experience with these models. This could be due to low fuel pressure from the supply pumps (there are three on each engine). This is the most common issue as they are diaphragm style pumps as they do have a limited life span. You can test these by squeezing the primer bulb as the engine starts to slow... if it picks up when you squeeze it then the low pressure pumps are failing.Next, the high pressure pump inside the vapor separator tank (VST) has a screen on it's intake that gets clogged. This requires some mechanical know-how as you need to disassemble VST to get to the pump.Next, Water contamination in the fuel is a big issue now days with the ethanol blended fuels that we are using. if the fuel filter that you are referring to is the plastic canister that unscrews and has screen it it then that is also a water fuel separator and had a red ring in the bottom that floats when water is in the bowl. So if the ring is floating off the bottom then you need to remove it and empty it out. If it has been running with water in the fuel system and the seperator has not been maintained then water has most likley made its way to the VST and could also be the sole cause of the issue. There is a drain (brass screw) on the bottom of the VST that you can remove and drain the tank...while the screw is out use something to catch the fuel(a clear container is best), make sure your batteries are off and give the primer bulb on your fuel line a couple of squeezes to purge out the tank. let the fuel settle for a minute or two and if there is water in it you will see it at the bottom of the container. I hope this helps,Try these steps and get back to me with your findings and we'll take it from there.
Expert:  Michael replied 1 year ago.
Were you able to check the suggestions I made? If you would still like to talk on the phone, let me know where you are located and what is he best time to reach you.
I wanted to start with the Q&A format so that I could list out some things for you to check... when you report back with your findings it will make it easier to get to the bottom of the issue if we were to talk on the phone. We can also continue this way if you wish.
Expert:  Michael replied 1 year ago.
Do you still need help, Please let me know if I can continue to assist you, otherwise if you feel my answers have helped then please don't forget to click on the accept button so that I will credited for my time.

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