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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3729
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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I own a 2003 225 Mercury Optimax. Approximately a year ago,

Customer Question

I own a 2003 225 Mercury Optimax. Approximately a year ago, I went fishing. The engine initially ran fine, 5600 rpm, as usual. After a 2 hour stop, I started the motor. It sounded like it was missing. It ran 5600 rpm once on plane. I went about a mile and then it dropped to 5400 rpm. I instinctively hit the trim button to trim it up and it lost 300 rpm. But, when I let off the trim button, I gained the 300 rpm back. The next time I had the boat out and started the engine it sounded rough at idle. Again, it would get up to 5600 rpm. But after running a couple of minutes, it would drop to 5400 rpm. I took it to a local marine shop and they ran extensive tests. They could not find anything wrong so they decided to send the injectors to Floriday to be cleaned. Once, they were reinstalled, it did not change a thing. They checked all the obvious areas--spark plugs, spark plug wires, coils and compression. Nothing appeared to be wrong. I then took it to shop #2. They ran extensive tests and even tried different wiring harness. It did not change a thing. Once again, hitting the trim button caused a loss of 300 rpm just like it had previously. I then took it to shop #3. They also did extensive testing. They found that the gasline inner liner was deteriorating and felt like the fuel might be contaminated. So, they replaced fuel line, cleaned fuel system and replaced two spark plug wires. The next time I took it out, it would only get up to 5400 rpm but I could trim up without losing the 300 rpm so it seemed like that had helped. The third time out on the water it ran 5400 rpm. But after a 3 hour stop, when I started the engine, it was idling rougher than ever and took about 30 seconds to get up enough speed to plane out. 4800 was the top rpm at that point. I took it back to shop #3 where they have had the boat and motor for approximately 11 weeks. I talked to them on June 16, and they told me that they have exhaused all avenues to fix the problem. They cannot determine was is wrong with it. Have you had any experience with this type of issue?
Submitted: 2 years ago.
Category: Boat
Expert:  Charles replied 2 years ago.
Hello, my name is***** you for allowing me to assist you today.
Would you please post the serial number if the engine?
Customer: replied 2 years ago.
Serial #0T687943; Model #1-225D73AD
Expert:  Charles replied 2 years ago.
Have any of the shops tested the fuel rails for leaks?
Do you have a gauge that can read over 100 PSI?
Customer: replied 2 years ago.
Not sure on the fuel rails. However, shop #3 said that they fuel system seem to be in order after I took it in again. The problem seems to occur after I restart from stopping for a few hours out on the lake. Not sure on the 100 PSI.
Expert:  Charles replied 2 years ago.
How about one that will read at least 50. There are a few tests that you can do.
Customer: replied 2 years ago.
My boat is still at shop #3. It is about 50 miles from where I live and I cannot get until the weekend?
Expert:  Charles replied 2 years ago.
I can give you ideas to try, we can wait until you have the boat, or you can accept the offer for a phone call and you will get me cell number so that you can call me when you are ready.
Customer: replied 2 years ago.
What ideas?
Expert:  Charles replied 2 years ago.
On the rear of the VST is a test port. Hook the gauge to that and turn the key on, it should read 25 PSI.
Then move the gauge to the fuel test port. Turn the key on, the pressure should go to 40 while the pumps run, and then drop and hold around 20 PSI. If the pressure falls totally off, it is a grommet inside the VST. If it holds, turn the key off and on a few times allowing the pumps to time out each time. Then press the air test port, see if you get any fluid from it at all.
Stat the engine on a hose, after it has run for a few minutes, press the air test port again, is the any liquid there at all, if so is it gas or water?

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