www.iFourWinns.com

I have a 2007 Horizon 240 w/Mercruiser 350 MAG MPI.

It generally performs pretty well, gets up to about 50 mph and the engine sounds smooth.

Occasionally, however, it will lose power and suddenly I can only go about 30 mph or so. When this happens, if I stop and try to get back up on a plane again, the engine feels weak and even sounds like it's misfiring if I give it too much gas. If I wait a while it seems to be okay again, at least for a while.

Thinking fuel might be bad, I ran it down to 1/8 of a tank, then added a bottle of fuel enzyme stuff and filled it back up with premium. It seems a bit better, I think, but the problem still does happen occasionally.

I also replaced ~part~ of the fuel filter. This is the GEN 3 Cool Fuel module -- it has a cylindrical filter element, which I replaced, and a flat disc filter that I don't really know how to replace. I tried pulling on it with needle nose pliers but I'm scared I'm going to break something. This is what the filters look like:

http://www.ebay.com/itm/Mercruiser-Mercury-Gen-3-Cool-Fuel-Module-Filter-Kit-35-866171a01-35-892665-/141481128133

So my questions are:

1. How do I replace the flat disc filter?
2. Do you think replacing this filter will help?
3. Could this still just be bad gas?
4. Does this sound like a different problem altogether?

Doesn't sound like gas to me. Fuel pump maybe, or obstruction.

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Mike
2005 Four Winns 230/240
VP 5.7GXi/DP
1998 F-150 XLT
Boat Pic

Could the remaining fuel filter cause somewhat sporadic performance problems?

I'm not so familiar with the fuel filter setup used by Merc. Hopefully someone who is will chime in. But in theory, yes. Volvo has a service bulletin specifying the permanent removal of a small filter on the input side of the fuel regulator for that exact reason (though I'm not sure the existence of that part has caused such a severe problem as you're describing).

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Mike
2005 Four Winns 230/240
VP 5.7GXi/DP
1998 F-150 XLT
Boat Pic

Well I got the flat filter replaced, just had to pull harder and it came out.

This is what the old and new ones look like --


New: https://drive.google.com/open?id=0B9y1jXxqS2s2dGpQdjdGTkNmSkE

Old: https://drive.google.com/open?id=0B9y1jXxqS2s2eEVHTnREc0c2RFk


Haven't gone out for a test drive just yet. Hopefully this will help.

Did you also replace your regular water separating fuel filter and did it look the same inside? If so I might want to look inside the gas tank to see if it needs to be cleaned out. The other thing that can cause a stumble like that is a clogged anti siphon valve on the gas tank.

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

I did, no picture though. It had some black spots. If I encounter the issue again I'll check out the anti-siphon valve.

Black spots might suggest a fuel line breaking down from the inside out. This boat is new enough to be fully compatible with E-10 fuels (not sure if you have to use it, we do no choice here) but I'd like to eventually remove the cover over the fuel sending unit and carefully, lift that out (5 screws or bolts) and shine a bright flashlight down to the bottom of the tank, see if it looks clean down there or not. Sometimes you have to clean the tank out. Not too likely as new as this boat is. Even my old tank ('88) was clean the last time I checked it (about 4 seasons back, replaced the gasket under the sending unit).

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Also check the O-ring under your filler cap. That could break down and cause black dots also, and could let water in.

That yellow staining on the flat filter looks suspicious; like it could be caused by the crap you get when water gets into E10 fuel (phase separated ethanol/water mix)

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"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings

New filters didn't help. Now the engine is overheating, so trying to put on a new impeller. I'm having a really hard time getting a new impeller installed on this Merc 350 MPI / Bravo 3. Crazy, this is supposed to be an easy job. On my Volvo Penta I could swap an impeller in 5 minutes.

I've got a new anti-siphon valve installed, that was actually pretty easy and quick. Haven't been able to test drive yet since I'm still struggling with the impeller. Ugh.

Turns out all this time there had been some overheating and the engine went into guardian mode. The alarm speaker was unplugged so I had no idea.

Shop threw on a new raw water pump so no more overheating and she's back in the game.

Nice follow up, this will help someone with the same problem.

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II