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2002 BF225 RPMs and Power dropping at 3000rpm only under load

N

Nasty Wendy

Regular Contributor
**This is the repost of my original thread. I'm attempting to streamline the thread down to usable information as suggested. Posts by other members of the site will appear as quotes. Quotes may have been edited to omit non relevant content.**


OK guys one of my twins has decided to be a problem child. It runs fine in neutral up to 6000 + RPMs. In gear it'll only go up to 3000 before it starts coughing and bucking. It has to be under load to do this. If I bring the other engine up to 4000 rpms first I can get the "problem child" to run up to 4000 rpms. If I try to give it any more throttle it'll cough and buck in protest but it will ease up to 4200 but then cough and fall back to 4000. No alarms no lights. New fuel pump, new fuel filters, new fuel pressure regulator, cleaned fuel injectors (replaced one), cleaned the screen at the regulator, cleaned the screen under the fuel pump, new spark plugs (NGK IZFR6F11), primer bulbs function as they should, compression is great in both engines. The other engine "The good son" runs off of the same tank through the same fuel filter and water separator and runs perfectly whether it is running alone or with the "problem child". I'm STUMPED.

It passed the compression test though with flying colors. The engine only has 500ish hours on it. I swapped ECMs with the "Good Son" and the problem persisted. ?????
 
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chawk_man said:
At 3950 rpm the ECU activates the the intake air bypass by opening vacuum to the vacuum diaphragm that sits right in front of the cover to the high pressure fuel filter - that's the one you move aside to get to that filter. I suspect that you are experiencing a vacuum leak when that is activated. First check the vacuum hose to be sure it is connected on both ends and has no holes in it. Next, remove the diaphragm itself, push in the arm all the way, and place you finger over the nipple the vacuum line attaches to. The arm will come back out a little bit but should stay there until you remove your finger. If it doesn't, then you have a bad diaphragm. Unfortunately, that is not a replacement part. It comes integral to the entire IAB. See part 4 in the following link.
http://www.boats.net/parts/search/Honda/Outboard Engine/2002/BF225A2 LA/INTAKE MANIFOLD/parts.html

While you are doing that, pull the lever that the diaphragm arm connects to on the IAB, pull is out a bit and make sure it springs back in place. If it doesn't, send me an e-mail at [email protected] and I will send you a write up on how you MAY be able to fix it.

If all that checks out, then take a look at the IAB valve assembly (part 9 in the above diagram) and check to see if that is functioning correctly.
Click to expand...

12345
 
Well after disassembling the entire IAB assembly I have it clean as a whistle. I used brass whool to clean up the insides of the bushings that the shaft rides in. I lightly polished the shaft sections that rides in the bushing with 600 grit sandpaper. I gooped in some industrial "never seize" and reassembled. It is as smooth as butter again.
 
chawk_man said:
The IAB has a set of baffles that mount on top of the engine air intake. At low rpm's, the baffles remain parallel to the base, allowing for what engineers call resonance charging of the intake manifold and combustion chambers. However, when the engine reaches 3950 rpm, the ECU activates the IAB Control solenoid that opens intake manifold vacuum coming from the vacuum tank to the IAB diaphragm, which in turn, moves the baffles to a 45-degree angle. When rpm's drop below 3750 rpm, the ECU turns off the vacuum, and the baffles (hopefully) return to their parallel state. Technically, what the IAB does when activated at 3950 rpm is initiate an inertia charging effect which draws a higher volume of air under more pressure into the combustion chambers under higher rpm's.

If, after you have determined that the manifold is working properly by manually pulling the arm to the baffles out and observing it to snap back in place, and tested the diaphragm that it holds a vacuum, then the way to test the whole system is in a test tank or in the water with the cover off and prop removed. You may also need to peel back the right side of the upper cowling so you can observe the control arm coming off the diaphragm.

Rev the engine to 4000 rpm. At about 3950 rpm the ecu should open a valve on the IAB solenoid that introduces vacuum to the diaphragm that sits right in front of the HP fuel filter. When that happens, the arm on the diaphragm should retract and pull open the lever on the intake manifold (which changes the angle of the baffles in the manifold.) When the engine drops back to 3700 rpm, the vacuum is released and the baffles should spring back to their normal position.

Item # 4 at: http://www.boats.net/parts/search/Honda/Outboard Engine/2004/BF225A4 XA/INTAKE MANIFOLD/parts.html
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Well I put the IAB cover back on and the engine is running perfectly in my yard. I'll try to splash the boat and give it a test out in the water soon.

 
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Sea Trial'd it and it was not the problem. The IAB system is working flawlessly but the boat is still suffering the same symptoms as the original post states. I'm thinking my next move is to test the fuel pump. I'll hot wire it run and measure the amount of fuel it pumps out. Anyone know what the flow specs are for our fuel pumps? I'll go through all the filters and screens again as well. Just to make sure I'm not forgetting any I'll check: Low Pressure fuel filter, High Pressure Fuel Filter, Fuel Pump screen, Screen below the Fuel Pressure Regulator. Am I missing any?

Wouldn't the O2 sensor give a Code/Light if it were causing this?
 
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chawk_man said:
A failed HO2 sensor should not cause the problem you are having. It will just make the engine run rich and your plugs will show the black soot rich running will generate. A failed HO2 sensor will not necessarily trigger an alarm, depending on what ECU you have.

Fuel pressure at the relief bolt on top of the HP fuel filter should be between 42 and 49 psi.

According to the Helm manual, if you disconnect the fuel return hose from the fuel pressure regulator and route it into a jar, then activate the fuel pump for 2 seconds, you should get at least two ounces of fuel discharged into the jar.
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OK I got back on it today. I installed the fuel pressure gauge and fuel pressure seems fine. It is reading *36psi at idle and it goes up when rev'd as vacuum goes away and drops back to 36 when it comes back down to idle. I pulled the air intake and fuel rails off. I'll post pics of the screen under the fuel pressure regulator as soon as I remove it, maybe later tonight.


* This was the first indication of a fuel flow problem. I thought 36psi was ok being that there is a vacuum line on the regulator which reduces fuel pressure at idle and on deceleration. WRONG!!! Idle fuel pressure should be as chawk_man stated 42-49
 
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A little crud on the screen in the fuel rail under the fuel pressure regulator but in no way plugged up. Click link for pic.

https://scontent-dfw5-1.xx.fbcdn.ne...=880a3e0b9bb04a535c5223ec338e8fe3&oe=5B41BF57
26904723_2503078843250643_4030135451508400046_n.jpg
 
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chawk_man said:
That filter is really bad! Considering all of the filters and screens the fuel must go through to get to that filter, those things should be sparkling clean, or possibly have an extremely fine black coating on them like you often see on the HP filter. Given that, it looks to me that the entire fuel system was compromised.
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12345
 
I'll be pulling the filters for inspection next. I wonder if I'll find them caked with this stuff. It will be a mystery if they are clean huh? It is already a mystery where its coming from and what it is.
 
Skooter said:
You need to pull the screen under high pressure pump. Its pretty much stuck in there with plastic tabs to the inner wall and an o-ring. I've pulled on them with needle nosed pliers. Your best best is to replaceit and the high pressure pump (if you have not replaced it before) For the $200 on the pump might as well do it. Also make sure you go in with new o-rings on the vst and high pressure filter. This is the junk I got from under the high pressure screen on my 200s
View attachment 16961
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I installed inspection hatches in my fuel tanks. Looks like I need to use them. I'll open them up and look inside. Fuel travel path will be addressed.
 
Culprit it found or one of the culprits found. The gasket material from the recently installed inspection covers is disintegrating. This was advertised as gasoline safe material. I'm pizzed about this. False advertising at its finest. The pieces in the tank break when I try to grab them with a reach tool. Looks like this is what has fouled my on board filters. Click links for pics of crud in fuel tank.
https://scontent-dfw5-1.xx.fbcdn.ne...=40249f8ca0dce4ed3593fd7b8efb4870&oe=5B081FCA
https://scontent-dfw5-1.xx.fbcdn.ne...=0a464e639fa28abd699a7440b1a3b484&oe=5B123958
https://scontent-dfw5-1.xx.fbcdn.ne...=c19784d10d2972630e39f82d85b34070&oe=5B00EDD4
https://scontent-dfw5-1.xx.fbcdn.ne...=7862a1117f676c3402a1807396b9e3a1&oe=5B4A5ADC

As for on board actions I'll get this out of the tank and replace all the gaskets and filters. Of course I'll flush out the lines and replace if fuel doesn't clean up. Motor wise the plan hasn't changed. I'll go through the fuel path and clean it out of all debris. I have to source a fuel safe gasket material that is *ACTUALLY fuel safe for real.

*The gasket material that was causing the problems was material I installed. I'd asked for a gasoline safe gasket material but I guess the kid helping me was paying more attention to twitterbook than to me. I was sold very not safe material for use with gasoline.
 
chawk_man said:
That's seriously nasty! I guess it clogged and overwhelmed your Racors. Think it through - that stuff had to get through the Racors, get through the LP fuel filter and the onboard fuel/water separator to get to your VST. Then more had to get through the screen on the bottom of the fuel pump, the screen and filter past the fuel pump and clog up the fuel rail filter. I would keep looking if I were in your shoes.
Click to expand...

*As it turned out the gasket material disintegrated into black debri and powdery black nastiness. Nothing got past the high pressure filter on the fuel pump. The crude on the filter that resides under the fuel pressure regulator was probably what 16 years of normal accumulation looks like.
 
I found a source for Nitrile aka Buna N gasket material. I'm using 1/8" thick material to have a good bit of squish to seal better.
 
Fuel tanks emptied cleaned and new Nitrile gaskets in place.

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Fuel tanks cleaned (again) and buttoned up with fresh stabilized fuel. Pick up tube and fuel line to filters cleaned. Tomorrow (hopefully) I'll finish flushing out the fuel lines up to the engine's low pressure filter and install new on board filters and start flushing out the fuel lines on the engine. Goal is to get the engine ready for the VST to be reinstalled. Currently I have the fuel pump running to test the fuel pressure. Its been running nearly an hour now and the pressure is holding. I'm testing it in a relatively static environment as the only release of pressure is the constant discharge of the fuel pressure regulator. It is holding a between 60 and 75psi. It'll jump up to 75 ish psi when the battery charger kicks on to keep the battery voltage up. As long as the voltage is 12 or higher the pump has produced a steady 60+ psi. On a running engine this will fall because of fuel injectors firing and my return hose from the regulator is smaller than the one on the engine so I'm sure that has a little to do with the higher numbers. I'll reassemble the VST and put the fuel rail and VST back on the engine tomorrow.

A very interesting observation is that when the upper feed hole to the fuel pump housing is not submerged in fuel it does not hold steady pressure. It sucks air from there and pressure fluctuates and drops radically. This could be a clue. Maybe the trash was obstructing flow to the point that the high pressure pump sucked down the VST enough to expose the upper feed hole of the pump housing to air. ????? I am eagerly anticipating the next sea trial.
 
This is encouraging. Fuel pressure is up to 44 psi at idle. I'm buttoning it all back up and doing a sea trial when wave heights come down from 6' in our LAKE.


27067621_2514642442094283_3517896874645066592_n.jpg
 
The problem is gone!!!!! Just returned from the sea trial and hallelujah the issue is gone. Thanks to everyone for all the help and suggestions. So now its oil changes, wash, wax and back into its storage shed at the marina.:)

***Remember the question regarding why the other motor wasn't giving trouble? Well it was but I wasn't able to expose it do to the issues with the "Problem Child" motor. The issue showed up on the Problem Child 1000rpm sooner so I never got the other engine up high enough to expose the problem with it. During the sea trial the other engine starting doing the same thing as the original Problem Child due to the Problem Child being able to turn enough rpms to expose the limitation of the other engine. After the filters were changed BAM no issues. The "other" engine's symptoms never got as bad but they were there and I'm sure if I hadn't cleaned out the tanks and purged the lines it would have gotten just as bad or worse than the Problem Child.
 
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