2001 merc 225 efi Does not like W.O.T

[biloxicbet]

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I am running a 225EFI on a Proline 23WA. I have been fighting the same problem since last season. After running about 10 minutes, 4 or 5 miles at WOT, around 5400 RPM it starts to loose power. (If I stay below 4K it will run further, not sure how far though.) There is no spitting of sputtering, It is not a rapid drop, it takes asbou 10-15 seconds and goes from 5300 down to around 3000, and will continue to drop off until I back off the throttle. I back of the throttle for about 1 minute or so, and it will throttle back up to 5k but within a couple of minutes it starts to drop off again. The engine does not die, but it does eventually start to run rough, plugs start to foul out. I know it sounds like fuel starvation but if that were the case, after I back off the throttle and let it "catch up" it should run about the same distance again before it backs off again. What I have tried so far in the last 30 days... Any suggestion would be appreciated.....

-took to service center, they said they cleaned the fuel system and it test ran good, I took it out the problem was still there, I dont think they ran it long enough at WOT
-rebuilt manual fuel pump
-replaced racor in bilge
-replaced primer bulb (quicksilver part)
-replaced fuel lines from tank to manual pump
-replaced engine mounted separator
-checked final filter on high pressure pump in vapor separator (clean)
-measured output pressure at high pressure pump (good)
-checked bleed off time for high pressure side (good)
-new plugs, correct type and gap from dealer
-new impeller, just in case it was a temperature issue, (temp good at 140 -150 no alarms)
-drained the fuel tank, added 55 gal none ethenol with quicksilver fuel system cleaner #2
-two new batteries.
-compression check (cold) all cylenders 110 - 120.

[thegreatwhay]

Similar Problem

Yo B,
I have a MAG 350 MPI engine that is doing almost the same exact thing. I have gone through and checked filters, tested Fuel Pressure...and I am posting here in hopes that someone who gives you an answer can also kill two birds with one stone.
Mine actually begins to stall at a lower rpm however...and I can watch the Fuel Pressure drop slowly/sporadically once I do get up to 3000 rpm, and if I do not back off the throttle, it will spit, sputter and die...Once I back off, it regains the pressure, and I can repeat...
So hopefully we both can find resolution. Sorry I do not have resolution for you.

[laguna21]

Merc 225 efi stalling or shutting down at speed

I have a 2001 225 efi as well

Recently it was shutting down at about 3400 rpms after running for 5-10 minutes. It would then start right up again. again at speed it would then shut right down while cruising.

Changed all filters and had fuel pumps checked.

Problem remained

Turned out that the plastic pick-up tube in my tank had a small screen in it. A very small amount of debris built up within the straw at this screen. At higher speeds I was not getting enough fuel. Idled and ran fine up to 2000 rpms, but not when larger amounts of fuel were needed.

I removed the debris and the small screen from the tank pick-up and the problem was fixed. I do have canister fuel seperators so the screen in the pick up tube was not needed anyway.

You can check for this condition in several ways.
1) run your engine on a seperate portable tank and see if the problem is still there.
2) use a seperate mechanical pump and see if you can pump gas out of your tank into a bucket. Do this right where your fuel leaves your tank, before any additional filters. Compare the flow to pumping from one tank to another.
In my case, the gas barely came out even with the high speed fuel transfer pump. After removing the screen from the tube, it pumps normally.

good luck

[laguna21]

Merc 225 efi stalling or shutting down at speed

Just worked on another one of these 225 efi's and the motor would "stumble" after running at 3600-4000 on plane for a few minutes. It would then continue to "stumble" or stall after short bursts of being on plane. Ran perfectly at dock and up to 2500 rpm's or so. Could drive it around all day but not above 3400 rpm's.

When I went to check the fuel pump, I found that the newer plastic fuel line had become compressed by the clamp and was actually loose on the bottom fuel pump nipple.

The pulse fuel pump runs on suction so if any of your fuel line connections are loose at all, air will get sucked in instead of gas. This is especially true at higher rpms and will make your engine run lean or stall out.

Before you spend a lot of time and money on parts, check every fuel line connection with a screw driver.

[laguna21]

Update
after tightening the fuel hose at the fuel pump in the above post, the boat ran better but the ball still did not get hard and the boat was hesitating.

What I found was that the hose from the ball to the fuel pump was delaminated internally (which is also why I thought initially the hose was loose)

This was only a one year old hose (USCG approved B1-15) but it had an inner clear membrane that had completely separated from the outer plastic hose. The hose looked brand new on the outside, but was totally messed up inside.

When I first checked the hose for obstructions, I disconnected the fuel line at the engine and squeezed the ball and fuel came out easily. Unfortunately, fuel pumps don't work that way. The fuel pump sucks fuel from the end of the hose like a straw instead of pushing it from the ball. The sucking closes down the inner membrane. Pushing the ball opens up the collapsed membrane.

Close your lips and lightly blow out. air escapes.
Close your lips and suck in. your lips seal and no air enters your mouth.

Once the hose was replaced the boat ran great and the fuel ball was rock hard even at 4500rpms.

[mojorisin']

ethanol

this could be the result of ethanol blended fuels being used. I worked for years with a manufacturer of underground flexible plastic fuel piping for gas stations. Ethanol blends can swell fuel system polymer materials if they are not made to handle ethanol and can cause problems such as this.

Not being in the marine industry I don't know how the various fuel system manufacturers are handling ethanol and other oxygenate blends (think MTBE and methanol). Unfortunately when buying fuels at the gas stations some states do not mandate showing when ethanol blends are being sold so you may be getting it and do not know it.

10% to 15% ethanol / gas blends are the worst for fuel systems that are not made for ethanol. Even 100% ethanol is not as bad as the 10% to 15% blends when it comes to swell and degradation of materials.

[Ski]

Good job finding the problem, For "thegreatwhay" guy trouble shooting similar, Use a separate fuel source and hook it right up to the motor at the filter/separator. If the problem clears then its either the anti-siphon valve or your pickup is plugged in the tank. In some installations a inline "can" filter is in the fuel line, If it out of sight then it is probably original. I have been burned by these before.

If the problem still exists I would replace the fuel pump, Hope this helps