2003 and 2006 6.2L Horizon Fuel Filters

[Greg_E]

New boat for me. One engine has the cool fuel III module while the older engine has the older style fuel cooler with the spin on filter. In addition to those fuel filters there are two small inline filters, Mercruiser part number 35-864572. They do not appear to be part of the original installation. At the very least I have to move those filters because one is mounted with tie wraps to a deck support directly above two of the batteries. I am considering replacing them with two 10 micron Racor water separating fuel filters. I would much rather collect any water before it reaches the cool fuel modules and the racor filters must have at least 4 times the surface area of the inline filters.What is everyone else doing?

I also found aftermarket replacements for the Cool Fuel III pleated filter. I have read that some people tried the Sierra 18-7977 and Wix also has a replacement WF10173 also sold at NAPA or O'reilly's as 600173. NAPA is only a little cheaper than the OEM filter but easier for me to get and I always liked Wix quality. Is there any aftermarket source for the disc filter in the CF III? Spending around $140 for fuel filters for one engine just seems crazy.

 

[alldodge]

My guess is the PO didn't like paying the cost of the Gen 3 filters so they added the inline filter trying to help make it last longer. Either that or they had some fuel issues and added the extra.

Starting with S/N 0M336102 the boost pump and extra filter was added for the Gen 2 cool fuel to help with the vapor lock issue.

Wix filters make NAPA filters, this is why Wix starts with a 7 and the NAPA doesn't (Exp 71234 and 1234), and have not foun a aftermarket for the disc

 

[alldodge]

Would also add, the disc is just a screen, so if your careful just clean and reinstall.

If I ever get a motor with the Gen 3, think I'll just change it to the Gen 2. Heck they still use the Gen 2 for Alpha drive installs

 

[scoflaw]

The disk is where the water gets separated and usually gets black after a 100 hours. I would def. change that 1. The pleated one only catches the large stuff and I've got several seasons out of them by blowing them out yearly. Seems that some CF3 setups came with the small pre filters from the manufacturer and some didn't

 

[Greg_E]

Thanks for the reply. I was thinking the same thing, if I should need to replace the Cool Fuel III module. What would be needed to convert to the older style? I see an aftermarket kit that has a fuel pump, cooler and filter that goes for around $300. I could probably find the mounting bracket from an old motor. Also different hoses I would guess.

Good info on the disc filter. I'll be careful not to damage it and see if I can just clean it.

The serial number of the 2003 is prior to the one you listed. Is the extra filter the spin on filter near the cooler? where is the added booster pump mounted? I will have to check to see if that engine had the upgrade.

Racor has 2 micron filters that can be used as secondary filters. I'll have to see if they have one that fits the Mercruiser filter bracket for the 2003 engine.

I'm going to replace the inline filters with the Racor 10 micron filters. I already have the Racor filters from a previous boat deal gone bad. More filter area, water separating, and cheaper than the inline filters.

 

[alldodge]

The key with any conversion is to maintain the correct fuel pressure. Manual 24 indicates 30 psi at 1800 rpm

What would be needed to convert to the older style?

Have not looked in depth but since the same year motors (Bravo/Alpha) can have either pump and only difference is the drive, I would assume either would work. The Bravo moves more water then Alpha. Just need to change hoses, or may even be able to place the Gen 2 where the 3 is now by placing it inline. As before, need to look close to determine if that could be done.

Maybe muc may have some thoughts

The serial number of the 2003 is prior to the one you listed. Is the extra filter the spin on filter near the cooler? where is the added booster pump mounted?

The inline filter was mounted between the tank and boost pump. The boost pump was mounted above the fuel filter and came as a kit.

 

[Greg_E]

That diagram looks like what I have on the 2003 engine.
I think the inline fuel filter on the other engine may have been left in place when the engine was replaced in 2006.
I forgot to mention that these are straight inboards so the raw water pumps would be the same for both.
I'll deal with what is needed to make the swap, when there is a need to replace the CFIII. Overall the boat is in nice shape but there is a long list of small maintenance items that I need to catch up on. I Thanks again for your help.

 

[muc]

The disk is where the water gets separated and usually gets black after a 100 hours. I would def. change that 1. The pleated one only catches the large stuff and I've got several seasons out of them by blowing them out yearly. Seems that some CF3 setups came with the small pre filters from the manufacturer and some didn't

This is not how the system works.

The pleated paper element is designed to stop water from flowing thru it, so the water will get caught in the cup.
The only way water will get down to the disc filter below the cup is if someone ruins the paper filter by doing something like trying to clean it.

Never try to clean a paper fuel filter.

 

[muc]

New boat for me. One engine has the cool fuel III module while the older engine has the older style fuel cooler with the spin on filter. In addition to those fuel filters there are two small inline filters, Mercruiser part number 35-864572. They do not appear to be part of the original installation. At the very least I have to move those filters because one is mounted with tie wraps to a deck support directly above two of the batteries. I am considering replacing them with two 10 micron Racor water separating fuel filters. I would much rather collect any water before it reaches the cool fuel modules and the racor filters must have at least 4 times the surface area of the inline filters.What is everyone else doing?

I also found aftermarket replacements for the Cool Fuel III pleated filter. I have read that some people tried the Sierra 18-7977 and Wix also has a replacement WF10173 also sold at NAPA or O'reilly's as 600173. NAPA is only a little cheaper than the OEM filter but easier for me to get and I always liked Wix quality. Is there any aftermarket source for the disc filter in the CF III? Spending around $140 for fuel filters for one engine just seems crazy.

Agree that running a gas line above batteries is never a good idea and installing a fuel filter above them is even worse. I would relocate the in line filter for the engine with the gen2 system with boost pump and remove the in line filter for the gen3 engine.

All fuel filters create a restriction. How much your Racor's will add I don't know. MerCruiser doesn't recommend/allow any additional restriction in their fuel system. If you want to add some it would be best to make sure your not adding too much. Might want to use a manometer for testing, they are cheap to build and very accurate.

All fuel systems have their own problems. What those problems are depends highly on the fuel that is run through them. Gas that you buy can have a different formulation depending on the laws/refinery's in your area. I'm in MN and we don't see anywhere near as many problems with the gen3 and Volvo paint issues. If you are in an area that does have this problem there are better ways to handle it (new fuel cell or clean the paint out of the one you have) than switching to an gen2 fuel system. They had their own set of problems, one of which was the band-aid boost pump that got added to some of them.

The gen2 is no longer used on any MerCruisers. The 8.2 is still using the gen3 but the 4.5 and 6.2 are using the FSM that seem to be working out pretty well. I think they got most of the problems taken care of during their use on the outboards.

 

[Fun Times]

Sounds like the boat is a 2003 year model with twin engines and someone installed one new complete engine in 2006.

More than likely the 2003 rigging hardware/engines, etc. included the inline fuel filters as that was typical on some/certain engine models like yours....Thus the new model engine with the cool fuel 3 module ended up utilizing the inline filter too.....Which incidentally the Gen 3's module aren't really recommended to have any inline filters from Mercruiser as it's said it could cause high restrictions in the fuel pump system.
The components of the fuel tank, lines, filters, fittings, pumps, etc. all contribute to a possible vacuum draw of going over the low 2 in. Hg. limit found in the troubleshooting/testing recommendations within service manual # 40.http://boatinfo.no/lib/mercruiser/ma...ser40.html#/32

That mentioned as I'm presuming you don't seem to be experiencing any known runnability issues with the fuel filters in place now? using a 10 micron by Racor "shouldn't" be too much more of an additional issue since Sierra equivalent part number 18-7721 to the OEM Merc filter part number 35-864572 is specced to be a 10 Micron filter as well so the Merc filter should be just about the same specifications though Mercruiser doesn't publish the info for this particular filter part number like Sierra is doing.

Sierra 18-7721 Mercruiser Fuel Filter Replaces 35-864572

Sierra replacement fuel filters are designed to meet OEM specifications. All Sierra Fuel Filters not only protect your engine, but are also over 90% efficient at removing engine damaging 10-micron and larger particles without starving the engine for fuel.

This fuel filter fits Mercruiser MPI & EFI engines with boost pump, 8.1L & 496 CID for 3/8" I.D. Fuel Lines.

Interchangeable with:

• Mallory
  • 9-37826
• Mercruiser Stern Drive
  • 35-864572
  • 35-864572T
  • 35-864572T01

With that mentioned I'm with muc of not recommending using the inline filter but feel the info is worth putting out there for you/all to choose which way you'd like your set-ups to be if you find it working or not as I've read both in years past....Some with found issues of using a filter and others don't.

 

[Greg_E]

Well there is a lot to think about here. The inline filter on the Gen III cool fuel engine can be eliminated, but what I don't like about that is if you do get water in the filter it is not easy to get it out, especially if you are out on the water. That also goes for the Gen II cool fuel with the spin on filter. While the small inline filters are not water separating filters, the Racors are, and it is a relatively simple task to drain the metal bowl. The larger filter area of the Racor vs the inline filter should help minimize any increase in flow restriction as the filters get dirty. Having said that 2" of mercury isn't much vacuum. I'm not looking to create a problem. I may try replacing the inline filter on the Gen II with the Racor and see how that works out. Still two filters but larger. Thanks to everyone that replied. All good information.

 

[scoflaw]

https://www.offshoreonly.com/forums...udget/357302-mercuiser-cool-fuel-filters.html

 

[Greg_E]

Thanks for the link to the OEM filters at a better price. Some other good info there as well. I have the CFIII Manual but, I don't recall seeing all the info found in the Service Bulletin that was posted, in the manual.

 

[scoflaw]

Service bulletins post date the publication of the service manual. That's my guess