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2001 Monsoon 325 5.7L MPI fuel filter micron ratings?


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Hi all,

When I bought my 01 Escape Wakesetter this past December (hurricane season, totaled boat from Houston) it had two in-line fuel filters (one before the fuel pump, one after). I was surprised to find that it did not come with a water separating filter.

Fast forward - the boat is on the water with a new engine, some re-used components from the old engine (e.g. CEFI3). I’m still chasing an engine bogging issue as i accelerate, and now suspect fuel filters.

For the rebuild, I replaced the first stage in-line filter with a water separating 10 micron filter. I replaced the other filter after the pump, as well, but suspect I did not use the correct micron filter and it may be causing my problems. I thought i was using the right filter sizes based on vendor information/part descriptions, but now suspect I’ve messed up and am choking my fuel system. 

Does anyone have ANY documentation to show what size filters should be used before/after the fuel pump on an Indmar Monsoon 325 5.7L MPI or similar? The configuration is CEFI3, 24# injectors at 3bar (43 psi), engine mounted pump, fuel filter before & after pump, GM fuel rail with fuel pressure regulator on return leg to tank. 

FYI - this is a new thread following up on my other thread. In troubleshooting, I’ve successfully confirmed TPS, IAC, ECT, MAP sensors, base timing, relays, etc. and replaced old Multec injectors with Bosch Design III injectors, among many other tests. 




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I'm sorry I can't answer the question directly, but if you have the correct pressure on the fuel rail at all times, you probably have the appropriate filters and pumps in line.

The only other thing I can think of is fuel hammer.  If you have hard crossover fuel lines (from one fuel rail to the other), you should change them out for ones with a short rubber segment between them.  Indmar identified a problem with the hard lines that cause a resonance from the injectors firing, and the solution is the rubber hoses to dampen the shock.  This site has plenty of threads about the fuel hammer problem.

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Hey justgary,

In my troubleshooting attempts, I recently replaced the filter after the pump and went to more rigorously characterize fuel pressure under load, but wound up stalling shortly after starting and created a fuel pump whine - obviously the filter was wrong.

My problem is that I have no idea what size filter is supposed to go there, and foolishly trusted a parts vendor on their word.

Fortunately I do have the soft crossover lines, so I don’t suspect fuel hammer.

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From Jimmy at Indmar - the in-line filter AFTER the pump is supposed to be 10 micron and matches the P/N you listed, John.

www.bakesonline.com cross references 556003 to Wix 33481, but the Wix website states the filter rating is 4 micron which is way too small for the intake side. 

I currently have the same spin-on 10 micron water separating filter you've listed on the low pressure side of my pump. I'm tempted to put no less than 10 micron, and really am considering a larger filter, for the in-line filter on the high pressure side w/ wrench flats & hard plumbing, although I'm not sure what it is intended to do.

Seems like placing a <10 micron filter in-line on the return leg is the effective way to go below 10 micron if you really want to polish the fuel. 

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  • 8 months later...

Can anyone post a photo of what your fuel filters before the pump are looking like? when i bought my 01 VLX it came with a cheap lawn mower fuel filter that i quickly found out was causing bogging problems, so i havent been running one. Id like to change that possibly, cheap inline generic filters always give me WOT issues.

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