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Dominick
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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I have a mercury optimax 225 efi outboard that has started

Customer Question

I have a mercury optimax 225 efi outboard that has started to run rough at idle. It will idle for a few seconds then die. If I put it in gear before it dies and throttle up, it runs fine. I put fresh fuel in it and changed the fuel filter and plugs. What should I check first?
Submitted: 2 years ago.
Category: Boat
Expert:  Charles replied 2 years ago.
Hello, my name is***** will be assisting you today.Would you please post the serial number of the engine?Is there a history of the engine sitting?When was the last time that it ran correctly?
Customer: replied 2 years ago.
The serial number is *****
It might sit for a couple weeks in between use. It did sit all winter and I treat it with stabil at ever fill up. It has slowly gotten worse since the start of the season.
Expert:  Charles replied 2 years ago.
Ok, Have you removed and inspected the spark plugs?Do you have a gauge that can read fuel pressure of 50 PSI?
Customer: replied 2 years ago.
I put new plugs in it a few days ago. To my eye they didn't look bad, I know more about cars than boats. I will have to rent a fuel pressure gauge. I'm assuming that the fuel rail will have the same test point as on a fuel injected car?
Expert:  Charles replied 2 years ago.
It has 2 actually. One for fuel and the other for air. Are you near the engine now and can do a bit of static testing?
Customer: replied 2 years ago.
It is a little late here. I don't want to make the neighbors angry. I will have to do the tests tomorrow. Will you be available tomorrow?
Expert:  Charles replied 2 years ago.
Yes I will be. I should log on after 10 AM CST. If you go out and get a gauge, make sure that it can read over 100 PSI, since it will be day light, you can run the engine if need be.
Customer: replied 2 years ago.
Thank you very much for your time. I will talk to you tomorrow.
Expert:  Charles replied 2 years ago.
Sounds good. Talk to you then.
Customer: replied 2 years ago.
well, I can't find a pressure gauge at my local auto parts store that will work with the connections on the outboard. Maybe I'm looking at the wrong thing. Can you tell me where I would hook up a pressure gauge? I thought it would be the two screw needle valves on top of the fuel rail.
Expert:  Charles replied 2 years ago.
It will go to the schreader valves. Like a tire valve stem. There is one on each rail.
Customer: replied 2 years ago.
I can't find a pressure gauge that will work around here. And I'm not ready to take it to the shop yet. As far as I can tell, all of the fuel lines are original and this boat is 16 years old. Would it be a good idea to replace all the fuel lines and clean the injectors? I have read that the ethanol in todays fuel will eat up the lines.
Expert:  Charles replied 2 years ago.
The lines from the boat to the engine, yes. The lines on the engine are high pressure and rather costly. Are you near the boat and can do a few tests?
Customer: replied 2 years ago.
yes
Expert:  Charles replied 2 years ago.
Ok, Can you supply water to the engine and start it so that it will idle?
Customer: replied 2 years ago.
ok ready to start
Expert:  Charles replied 2 years ago.
Alright, allow the engine to idle for a few. then using a screwdriver, depress the valve on the Port rail. Do you get any liquid from it, if so is it fuel or water. Then press the valve on the other rail, it should spray fuel. Have some rags handy, as this can make a mess.
Customer: replied 2 years ago.
Ok. I got air only from the port valve. a lot of fuel from the other valve.
Expert:  Charles replied 2 years ago.
Great. That is what it was supposed to be. Did the engine die while you had it at idle?
Customer: replied 2 years ago.
Yes. I had to act quickly to test those valves
Expert:  Charles replied 2 years ago.
Ok, Take the filter off the engine and pour it into a glass jar. Look to see if there is more than one layer in the jar.
Customer: replied 2 years ago.
I poured out the filter, looks like it is only fuel. no water. no layers
Expert:  Charles replied 2 years ago.
Any sediment?
Customer: replied 2 years ago.
nope. clean
Expert:  Charles replied 2 years ago.
Does squeezing the primer bulb help the motor stay running?
Customer: replied 2 years ago.
it seemed to help at first, but it still died. Of course it had to fill the filter back up. the bulb is firm, still dies wjhile im squeezing it
Expert:  Charles replied 2 years ago.
Alright, your motor has two electric fuel pumps. The low pressure is mounted outside the VST, the high pressure is inside it. Unplug the high pressure pump. Have a helper turn the key to the ON position, do you hear the low pressure pump run at all?
Customer: replied 2 years ago.
low pressure pump comes on. also, if i bump the throttle up a little past idle it will run. Not sure if this means anything to you.
Expert:  Charles replied 2 years ago.
Does the alarm work in the boat?
Customer: replied 2 years ago.
yes,
Expert:  Charles replied 2 years ago.
And you are not getting an alarm when the engine runs rough?I think that you are going to need the gauges after all. I need to know the pressures of the air and fuel. This is not going to be a simple one.
Customer: replied 2 years ago.
Great, I was afraid of that. Do you know where i could get the proper gauge for the mercury? without spending 200 bucks.
Expert:  Charles replied 2 years ago.
Most any chain auto parts store should have an EFI tester. Just make sure that it can read 100 PSI and screw onto a valve like a tire. Most of the time you can rent one due to the cost of them.
Customer: replied 2 years ago.
i will make some calls around town. thanks again for the help. hopefully i will find one by tomorrow.
Expert:  Charles replied 2 years ago.
Would be nice. I will be here for the rest of today, and sort of hit and miss tomorrow.
Customer: replied 2 years ago.
thanks charles
Expert:  Charles replied 2 years ago.
Your welcome. Let me know what you find out and we can go from there.