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225 Mercury Optimax drops power then come again

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225 Mercury Optimax drops power then come again

Old 10-14-2020, 03:03 PM
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Default 225 Mercury Optimax drops power then come again

My outboard is a 2000 Optimax 225 DFI. It has this weird issue of losing power then regaining itself. It runs well for awhile, then it drops power. After it drops power, it regains the power again and runs fine for awhile. Sometimes, it can't regain the power by itself, so I back out the throttle and I push it up again. Then it runs fine. There's no hesitation to regain power. Yesterday, during the trip of 70 miles, it happened for about 15 times. Do you think it's the TPI sensor and linkage? Where should I look for?
Thanks.
Old 10-14-2020, 03:19 PM
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Have you changed the fuel/water filter? Does this model have the VST, if so open the drain plug and check for water.
Old 10-14-2020, 09:27 PM
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Fuel restriction or air leak in fuel line losing pressure/volume
Old 10-14-2020, 11:45 PM
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I replaced all fuel parts including all fuel pumps. Don't you think it's the TPI sensor or worn out linkage?
Old 10-15-2020, 02:30 AM
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Originally Posted by stevechumo View Post
I replaced all fuel parts including all fuel pumps. Don't you think it's the TPI sensor or worn out linkage?

Including the fuel injectors? - I had this exact same problem on my 150 Opti and it was a sticky injector - I had them all cleaned and the problem was solved.
Old 10-15-2020, 04:05 AM
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I had the exact problem you are describing. After I cleaned the VST, fuel filters, spark plugs and wires it ended up being a faulty air injector. Local Mercury mechanic took care of it but it wasn't cheap. Good luck
Old 10-15-2020, 04:36 AM
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Check the wires and coil packs
Old 10-15-2020, 01:52 PM
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I had the air & fuel injectors cleaned professionally. I put in an aftermarket high pressure fuel pump Quantum. I think that it may lose pressure after a long run, so when the throttle is backed down, it's able to pump fuel again and regains power. Will that be the issue?
Old 10-15-2020, 02:08 PM
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How to test fuel and air pressure:
Old 10-15-2020, 07:04 PM
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Have you checked your block pressure sensor?
Old 10-19-2020, 02:12 PM
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I don't have the tools to test the pressures. I may have to bring the boat to the shop then.
Old 10-19-2020, 02:14 PM
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Battery?
Old 10-19-2020, 02:25 PM
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Originally Posted by stevechumo View Post
I don't have the tools to test the pressures. I may have to bring the boat to the shop then.
I bought two pressure gauges from eBay- they weren’t that expensive (I can’t recall exactly what now - probably Chinese made but for a once a year check I wasn’t worried about that) just check that whichever you buy has the right fittings.
Old 10-19-2020, 03:14 PM
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Vote for a sticky air injector
Old 10-23-2020, 10:41 PM
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I would rule out the bad injectors, because I had all 12 fuel & air injectors serviced by RC injector, which is also a fuel injector manufacturer. They gave me the sheets of before & after services. I did a 80 miles trip yesterday, and it ran better than last week. During the trip, the throttle was slowly dropped about 10 times.
The issue looks like it's a mechanical issue, because after the power was dropped, I just backed down the throttle and pushed it back, then it gained power without hesitation. Previously, I had put a 4th screw on the TPI, even though it wasn't there in the first place. I looked at other Optimax, and they only have 3 screws. I wonder if putting the 4th screw on caused the issue.

Old 10-24-2020, 05:58 AM
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Sounds like a coil to me.
Old 10-24-2020, 07:48 AM
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Originally Posted by davidwademarine View Post
Sounds like a coil to me.
X2. Also check plug wires, look for cracks. Sounds like you are dropping a cylinder
Old 10-24-2020, 08:18 AM
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I could be a bad plug wire that is grounding on the block. I chased one for about a month and finally found the pin hole.

Last edited by bluewaterpirate; 10-24-2020 at 08:28 AM.
Old 10-24-2020, 01:33 PM
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Originally Posted by Eightpter View Post
X2. Also check plug wires, look for cracks. Sounds like you are dropping a cylinder
If dropping a cylinder, then how could it regain full power right away when I pushed the throttle up then it ran fine for a very long time?

Last edited by stevechumo; 10-24-2020 at 03:03 PM.
Old 10-24-2020, 01:55 PM
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Your motor is going into limp mode had same issue on my 2013 250

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