I have a 02 380 sundancer w 8.1...

[filimili]

I have a 02 380 sundancer w 8.1 mercruisers . The in line fuel filters are primary to the water separating filters and I find this unusual . Shouldn't it be the other way around ? 

[wingless]

The 8.1 Mercruiser has a water separating fuel filter in the Cool Fuel Module.

When I examine the documentation for the 2002 380DA and for the 8.1 Mercruiser I only find the one fuel filter per engine, the water separating fuel filter in the Cool Fuel Module. I do not find an additional in-line fuel filter on the boat or on the engine.

Each engine and the generator all have electric / manual shutoff valves. The generator also has a fuel filter mounted to the engine room wall.

Where are the in-line filters? What is the concern?

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https://mercurymarine-gsdesign1.netdna-ssl.com/media/filer_public/1b/38/1b382ca8-4c81-4b74-92a4-197e80b6abd6/81l_horizon_owners_manual_864841062.pdf

[filimili]

The starboard in line filter is mounted to port of the engine on a fiber glassed stringer near center of engine compartment and it flows to the water separating filter . The one on port engine is mounted in similar fashion to port of port engine . The concern is that after replacing the in line filters ( which were not replaced during engine servicing ) the boat ran great . Took boat out again last weekend and the old problem recurred . Losing rpm after running for a few minutes at 3600 rpm . Marinemax says - like you - there should only be one filter . I bought the boat 4 months ago and overall it's a great boat , but can't live w this problem . Mechanic put psi meter and confirmed fuel pumps had good pressure . I think my next move is to bypass the in line filter and see what happens .

[wingless]

It sounds like those fuel filters were added by a prior owner.

They do not show up on the parts listing for the 2002 380DA, or for the 8.1 Mercruiser.

The standard water separating fuel filter in the Cool Fuel Module should be sufficient for the engines.

Follow the procedure (in the linked document) for removing water from the cup when changing the filter element. How does the fuel and water look in the cup?

It may be useful to remove a fuel sample, place it into a glass jar for hours, then examine for water contamination.

Use appropriate sealant on the threads when changing the fuel connections. Use extreme caution when working on fuel systems. Ensure no leaks and no fumes before proceeding.

[wingless]

Get your own fuel pressure gauge to use during problem operation. It will be more useful to have that information than making measurements when everything is fine.

[filimili]

Fuel was clean - no water . I agree that prior owner must have installed . After more research I've learned that added stress on fuel pumps could've damaged them . Just spoke to my mechanic . He's going to bypass the in line filter . If problem persists he's gonna replace fuel pumps .

[wingless]

Yes, the extra fuel filter will add a pressure drop that makes the fuel pumps work harder to maintain the specified operational pressure.

[filimili]

I'll keep you posted . I'd rather operate on a person than my boat , but I'm learning a lot .

[wingless]

Yes, the OR is cool, but keeping the boat running makes the Pakled in all of us happy.

[340_Sundancer]

My 04 340 Sundancer with 8.1's has this inline filter. It is shown in the SR parts manual. I do not have the water separator / filter in the cool fuel module. My engine has the spin on fuel water separator filter just prior to the fuel pump. My slip neighbor's 05 340 has the filter and water separator in the cool fuel module as Wingless is describing.

I'd give SeaRay a call.......