Secondary fuel water separator will cool fuel?

paulswagelock

paulswagelock

Well-Known Member
Oct 25, 2010
2,194
pa
Boat Info
2018 SDX 270 OB 300 Verado
Engines
Verado 300
I have a 2007 Mercruiser 350mag with the gen3 cool fuel system. Given the occasional high water fuel content at local marinas, would it be possible for me to install an inline canister type separator ahead of the cool fuel module? Worries would be pressure drop, fuel starvation, etc. Thoughts?
 
Last edited:
I think you have some valid concerns. Probably would not be a bad idea to call Merc.

How often are you changing the filter?

How much water are you seeing trapped in the filter when you change it?
 
I have changed it at the end of each season - approx 60-70 hours.

Can't tell how much water. by the time I dump the contents, suck up the remaining in the assembly, there is no way to tell.

Several boats have been stranded due to water from some of our local marinas, so I was hoping to provide an easy way to fix the probelem if it happens to me out on the water. The cool fuel module is not easily field serviceable
 
Do you have Smart craft gauges that would set off alarm for "water in fuel bowl"? I have and so far no indication of water but then I use marine fuel without ethanal. I have also considered adding a spin on filter in-line but others on this site said it was a bad idea for various reasons.
 
I do have the smart gauges. I have not seen that alarm though, and I have tinkered with them a bit. So that would alert me, but before a problem running the engine, or once the engine is affected?
 
paulswagelock said:
I have changed it at the end of each season - approx 60-70 hours.

Can't tell how much water. by the time I dump the contents, suck up the remaining in the assembly, there is no way to tell.

Several boats have been stranded due to water from some of our local marinas, so I was hoping to provide an easy way to fix the probelem if it happens to me out on the water. The cool fuel module is not easily field serviceable
Click to expand...

It sounds like you are changing it within the recommended intervals.

Once you remove the Filter assembly form the cool fuel unit and twist off the bowl and dump it, what you see there is some fuel along with any excess water that the filter caught. The bowl holds the water and contaimated fuel. Of course there could be some water in ther filter still but unless you see a bunch of water in the twist-off bowl, I would not think you have much to worry about. When I changed mine the first time, I only had a small bead of water in the bowl when I dumped it out.

I have never heard of sucking the remaining fuel out of the Cool Fuel assembly and will have to check but don't recall seeing that in the procedures. Not sure that is necessary.

If you have a 2007 and have not yet changed the micron filter, you may want to consider doing it next time. It is installed in the cool fuel assembly and sits right under the water sep filter canister.

See here- http://www.clubsearay.com/forum/showthread.php?t=27133

Maybe someone else can comment on what conditions must be present for the Smartcraft alarm to be activated as I don't know.
 
There's definitely a set-up out there that would work for you. You don't have some crazy, jacked-up high HP engine. While the concerns that you express are certainly valid, they are also easily overcome.

Just take a look at the specs for the particular filter set-up, based on max GPH. I'd probably suggest going with Racor as far as a brand (good company, made in the USA, been around for a long time, great products). I've only personally installed these on small OB's (a while ago, too), so I can't offer any specific guidance on which model filter to use. But, it is something that our shop has installed on many occasions on stern drives.

The suggestion to call Merc is a very good one. I'm a little skeptical if they'd actually give you a recommendation to install something that's not OEM, though. Can't hurt to try.

Here's Racor's number: (209) 521-7860. If it was me, I'd probably just skip calling Merc and go right to Racor.

By the way... If you're not already, make sure you are using healthy doses of a good quality additive (like Startron or the green Stabil). In your situation, this is pretty much a "must do".

Good luck and kudos on being proactive to protect your investment.
 
I contacted Racor. Their answer was "if your system can handle it, it is a good idea".
When pressed, the contact said it would likely be fine.

I guess the worst case is I will have to undo it, and be out $100 bucks plus my time.
Not sure what to do now.
 
So I contacted Mercury next and asked for their opinion. Here is the response:

It is not advisable to add an additional filter, our systems are very balanced as we design them and can not tolerate more than 2" mercury vacuum in the system before vapor locking becomes a concern at which point, your fuel pump would work excessively and would possibly fail more prematurely. I would advise you to diligently continue to check the water separating fuel filter and dump the water often to assure no problems with the fuel system on your engine.

So, it appears I need to regularly allow the boat to sit for 24 hours to depressurize, disassemble my cool fuel system, dump the contents, then reassemble. How convenient....

I guess I could install a vacuum gauge and check my factory design vacuum to see if there is room before I hit 2" Hg, but I don't want to be the guy riding in the bilge under full throttle taking readings!
 
Hmmm. That's interesting. Sounds like neither company wants to be of much help (Edit: Although, at least merc gave you the vacuum spec). Personally, I would just do it and not worry about it. But, maybe the newer Gen3 systems (I have the older one) are more finicky?

Honestly, I'd be surprised if the properly sized filter would really cause any problems. But not being an expert in this field, I also won't advise against what you're being told until I get more knowledge on the subject. I really can't believe that the Merc system is THAT tight where another filter would be a problem.

I 100% agree with you that it would certainly be much easier if you had a more accessible (and drainable) filter. Riding in the engine room? Yeah, been there, done that - it's a little hairy, to say the least!

Let's see if anyone else has personal experience or can talk more intelligently about it than me... before you either rule it out or go forward.
 
Last edited:
I'd carry a set of spare filters, and as Dennis mentioned, routinely add the appropriate amount of water suspension additive if you have problems with the marinas where you refuel. If you get a 10mm ratchet wrench, it will make the job of removing the canister bolts a slightly smaller pain.

I'm not sure what a fuel pump costs in a cool fuel system, but I suspect you could buy quite a few filters for the price of one.
 
paulswagelock said:
So I contacted Mercury next and asked for their opinion. Here is the response:

It is not advisable to add an additional filter, our systems are very balanced as we design them and can not tolerate more than 2" mercury vacuum in the system before vapor locking becomes a concern at which point, your fuel pump would work excessively and would possibly fail more prematurely. I would advise you to diligently continue to check the water separating fuel filter and dump the water often to assure no problems with the fuel system on your engine.

So, it appears I need to regularly allow the boat to sit for 24 hours to depressurize, disassemble my cool fuel system, dump the contents, then reassemble. How convenient....

I guess I could install a vacuum gauge and check my factory design vacuum to see if there is room before I hit 2" Hg, but I don't want to be the guy riding in the bilge under full throttle taking readings!
Click to expand...
There's your answer. I don't know how much more knowledgeable a source you could ask for. Maybe you should talk to the marina and find out how often they check their fuel system filtering, maybe they're unaware of the water problem.
 
Woody - my skepticism of Merc's response simply stems from knowing how reluctant they are to embrace other manufacturer's devices in combination with their products. The basis for this, I assume, is that it's easier for them to offer a blanket statement (and hence avoid any liability) than to test products.

Sometimes it's good to challenge the "man", 'ya know?

I wonder what Merc would say about using their older style (spin on) filter inline (upstream) with the Gen3? Those filters are only about $10.
 
you can install the racor which has the plug in the bottom for draining. remember don't get the one with the clear plastic bottom, you will need the metal bottom since its in the engine room. Or you can get the mercury kit that has the old style spin on filter that the replacement filter is only $10. I've installed both the racor and the merc kit on boats with the gen 3 systems and had no problem.
 
So you personally have added one inline with a gen III cool fuel system? How long has it been installed (looking for premature fuel pump wear as Merc suggests)?

Thanks
 
flflatrate said:
you can install the racor which has the plug in the bottom for draining. remember don't get the one with the clear plastic bottom, you will need the metal bottom since its in the engine room. Or you can get the mercury kit that has the old style spin on filter that the replacement filter is only $10. I've installed both the racor and the merc kit on boats with the gen 3 systems and had no problem.
Click to expand...

Changing the secondary spin on filter would be much easier than changing the module filter every year. The module filter could probably go for several seasons using 10 micron spin on.
 
I have personally installed the spin on filters about 2 years and 350 hours ago. no fuel pump problems. Just think not all boats are the same that a merc motor goes into with the fuel system. Some have double or tripple the fuel hose length and some have a few 90 deg. fittings also which will give more of a restriction.
 
My current layout is simple. There is about a 3 foot run of fuel line from the tank to the fuel module, little if any vertical lift in the run. To add the external one, would need to add about 12" of new line, and would introduce a 6" lift in the vertical run to get into the filter assembly.
 
That is fine. Some fuel lines in some of the larger boats have runs of over 10 feet with a few 90 deg. fittings. and there are no problems with them.
 
Flat - do you recall which model you used? Thanks for weighing in on this one. Experience is what we needed here.
 
You must log in or register to reply here.

Forum statistics

Threads
113,116
Messages
1,426,373
Members
61,028
Latest member
ddbyrd329
Back
Top