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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 15915
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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Have a 115 Merc 4 stroke EFI idles fine up to about 3000 rims

Customer Question

Have a 115 Merc 4 stroke EFI idles fine up to about 3000 rims then falls on it's face?
Submitted: 2 years ago.
Category: Boat
Expert:  Jason replied 2 years ago.
Hello my name is ***** ***** am I speaking with?
Does the alarm system work on the boat, does it beep every time you start it up?
Customer: replied 2 years ago.
Jamie, yes it only beeps when you cycle the key no other alarms!
Expert:  Jason replied 2 years ago.
Hi Jamie, do you have the ability to check the fuel pressure with the boat at the highest speed it will hit?
Customer: replied 2 years ago.
It's at 15 psi when it starts to stumble.
Expert:  Jason replied 2 years ago.
15 psi is the highest the fuel pressure will get?
Customer: replied 2 years ago.
I will see 20 at idle then starts to drop off, kind of surges then and drops off.
Expert:  Jason replied 2 years ago.
That's to low, it should be up over 40.
What you want to do is pump the primer bulb over and over and see if fuel pressure pickup up. If it does, there is an issue with the low pressure pump or fuel supply. But if pressure is still low there is an issue with the high pressure pump, or filters for the high pressure pump.
The high pressure pump is located inside of the vapor separating tank. There is a filter just below the pump. What you would want to do is pull the separator out, clean it out, change the filter, and this next part is up to you. 1. install a new pump at the same time and run it. 2. put it back together with just a new filter and run it.
If it a bit of work to open up that vapor tank, so in the shop we just replace it that way we don't have to open the tank up twice. But if you are going to DIY this, and if you don't mind the posiblity of having to take it apart twice, you might want to try it with a new filter in it and see what happens. Does that all make sense?
I think that should do it. If you had a further question on the issue by all means feel free to ask. If not, Just incase you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.
Questions do not lose out, so if you have to come back tomorrow or next week with follow up questions to this you still can even after doing a rating. And if I have saved you quite a bit of money, or saved you a trip to the dealer, tips are always greatly appreciated.
Thank you
Expert:  Jason replied 2 years ago.
Hello, just checking in. No rating has been put through yet so I wanted to see if you had any more questions on the issue? -Jason

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