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2006 BF225 Surging at High RPM

S

Shark Bait

Member
Symptoms:
Ran (5100 RPM) for 45 minutes
Trolled (800-900 RPM) for 4 hours
Throttled up to head home and the engine would get to ~3000 RPM and then drop quickly back to 1000 for a few seconds and then up to 3000 and back.... The fuel ball is very soft even afte multiple pumps. Pumping it while running makes no difference.

Had to hold at 1200 RPM to keep it running steady. (2.5 hours to get back to the barn.. ugh)

Thoughts:
Fuel Screen inside Vapor Separator is clogged

The VST has never been removed and the engine has approsimately 400 hours.

Plan:
1 - Replace RACOR
2 - Replace Low Pressure Fuel Filter
3 - Disassemble and replace Fuel Screen in VST along with all O-Rings.

Anything else you guys can think of to start with?
98a687b6-3d89-455f-a136-60c19a4fb498_zpsa7927881.jpg
 
Simple things first...I assume no alarms went off.

Try to duplicate the problem, then open the fuel fill cap. If it runs correctly, you have a clogged breather on the fuel tank.

Feel the pump up bulb, if it is partially collapsed, then the pick up in your fuel tank is clogged or the anti-siphon valve in the bulb has failed.

Pump the bulb and see if it picks up speed, if so, your low pressure fuel pump is likely bad.

Drain the VST completely using the clear plastic hose attached to the back starboard side of your motor and see if any junk or water comes out. If so, your onboard fuel-water separator, and/or your low pressure fuel filter has failed.

Pull and inspect/replace the high pressure fuel filter.

If none of that helps, then pull and clean the VST.
 
Thanks for the added inputs.

Chawk -
No Alarms
Fuel pump bulb is not collapsed, seem to be getting good flow from the tank.
Dis-assembled water separator / fuel filter assembly on the water and refilled using pump ball, again seem to get good flow from the tank. Not ruling out the main tank but does not seem to be clogged.
Fairly certain it's not the vent on the main tank, why, because of the rate that the engine ramps up and cuts out. I would think a 70 gallon tank if it was vapor locked would not lock up that quickly but more of a gradual change. Easy enough test but not very hopeful of a good outcome.

"Low Pressure Fuel Pump"? I'm only aware of 1 fuel pump on the engine that is part of the vapor separator assembly. Is there another pump?
 
It is covered on page 5-94 of the Helm shop manual. It is mechanical and runs off the cam. Cannot find a diagram but it looks like this.
 
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NICE!!! That looks pretty easy to access on the left side cylinder head. Should be pretty easy to disconnect the hose and run a test to make sure it's pumping?
 
Yep! To do it properly, you would need to know the minimum pressure spec and check it with a reliable gauge. I'm sorry, I don't have any documentation for this engine but I bet chawk_man jumps back in with it any minute. Hope that's your problem because that's an easy fix.
Good luck.
 
At idle (650 +/- rpm) fuel pressure should be 41 to 48 PSI on the output side. The manual says to remove the fuel pump and test the plunger by pushing it in and out. It should be easy and smooth. If stiff or rough, replace it. The manual is emphatic about the necessity to replace the big O ring upon re-installation.
 
Pretty sure I found my problem. Didn't get a full run out today but at the dock it definitely seems good.

Definitely wasn't easy, several screws required vice grips to remove. Needed to pull the entire VST assembly out to just get this done.
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Yep - that's ugly. That filter should be changed annually, but few people do it because they are not putting many hours on their engines. Vice grips on the bolts? That is ugly too. Hope you cleaned and checked the VST when you had it off.
 
YEAH BABY! Stuff like that kept my family fed and in a pretty great house for years! It's what pro mechanics call...CHA CHING!
Now, lets hope what was getting PAST that puppy isn't waiting in the lines to cause your more grief. New bolts and plenty of ANTI-SIEZE on the threads on reassembly will make the scheduled maintenance I KNOW you'll be doing on that in the future MO EZ.
Good catch!
 
Well 2 main reason I never touched it before now.
#1 - I'm a weekend warrior an the engine just rolled 400 hours
#2 - 3 Service recalls over the years I would have assumed the pros had at least swapped it out when they pulled the heads a few years back.

Yep, don't spare the never sieze and new bolts on everything.

Ran well today.
 
This is for both Shark bait and Capt. Jamie...Based on both your experiences, is annually a good interval for checking/changing that filter or would you say something different?
 
Owners manual says every 400 hours, which is OK if you are running 400 hours per year. I do it every year usually in late fall after rock fish season.
 
Ha ha, yeah chawk_man! We can see from Shark bait's photo that your caveat MUST be true, at least to some extent. And, I agree with him that if PROS were in there at any time, it probably should have been addressed then. Something for all to consider if having their engines serviced.

I'm in SoCal and we don't deal with ethanol. That filter looks as if it was stuck in the mud! Do you think ethanol did all that or is he getting fuel from the bottom of the Okeefenokee? I think I might be lookin' for a different service station.
 
Jimmy, Those HP filters are strange. It seems like whatever material they are made out of just deteriorates over time. After my fuel has been treated with StaBil, run through the Racor, then through the onboard f/w separator and the LP filter, then gets to the HP filter you'd think it would be pretty clean. But every time I change it out, it seems like it has been working overtime. Go figure. Cheap part, just a PITA to change it out.
 
I would definitely go with CHawk's recommendation and myself will be at least looking at the filter every 12 months. My biggest problem during the repair was corroded screws. If the screws were not corroded I would not have had to remove the entire VST assembly.
 
Make sure the screen under the high pressure pump is cleaned out. Also there is a "hidden" screen filter between the intake manifold and engine block. Mine had neverbeen replaced and they have metal ends on them that rust.
 
Skooter - If you are not talking about the HP fuel line screen, then exactly where is that "hidden" screen filter between the intake manifold and engine block? Anybody have a part number for that or where it is in a diagram?

This is a new one on me, but I haven't been that far into my engine.
 
Darn - after 6 years with this motor I'm still finding fuel filters and screens I had no idea existed. Besides the suspension strainer Skooter ID'd (PN 16915-ZW5-000), apparently there is another fuel pump filter (PN 16911-759- 003) and a screen filter under the fuel pump regulator (PN16614-P5G-003) that's also in there. All these are identified on various microfiche pages on boats.net.

None of these seem to be covered in the service section of the Helm manual, nor do they seem to be readily identified in any of the other sections. That's sure frustrating.

Am I all wet on these various filters and strainers, or are they really all there and need to be checked periodically?

Maybe we've just come too far from my days dealing with an old Ford 289 with a Weber 4-barrel for my aging noggin to comprehend.
 
I couldn't find my old one to take a pic, but it looks like this. Understand, I don't think mine was ever changed, so mine was yellowed and cracked and the metal ring was rusted thru.
hon-16911-759-003.jpg
 
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