Mercruiser Gen3 Cool fuel module water in fuel?

[JustJason]

I've been meaning to bring this up to you Jason due to I noticed you mentioned 4in/hg in your how to test fuel system in the stickies.
While the vacuum values will change with different fuel hose sizes used, fittings, etc. etc., The preferred values from both Merc and Volvo are 2 in/hg found in their literature. Just curious if you've seen other manufactures allow up to 4 hg?

When I was in school, what we were taught, is if you can not find a spec in a manual to use 4 in/hg as a generic value, That document in the stickies was originally written by Don. If you new Don he was a 1 finger typer, and did not always mince his words well. What I did was I took the original document (and this was 5 or 6 years ago) and I re-wrote it in order to make it easier to read, as well as added pictures. But I kept the original values at the time which was 4. On Mercury product, i'm pretty sure I have seen "up to" 4 in some manuals. I know a lot of manuals and TSB's say no more than 2.5. At the same time, I don't think I have ever seen anything ever (formally) on fuel restriction testing from Volvo, and quite a few other manufacturers.

On any fuel system, filters add resistance to flow. On the cool fuel you can not directly measure that because there isn't anyplace to tap in a vacuum gauge between the fuel pump and the filter. So you can only measure the resistance between the module itself, and the fuel tank. So what they (engineers) are probably calculating is the restriction of the filter in the module, and accounting for that already.

Just as an example, click this link and go to the last page.
http://www.parker.com/literature/Rac...Rev_G_110A.pdf

That comes from Parker/Racor. And if you look on the bottom left of the last page they go with 4 as well as a generic non-engine specific value. On a personal note, I've seen many a boat that show 3.5 to 4 on the needle and not cause a lack of fuel issue when they had good pumps. If any pump is worn out even 1 inch of mercury can be to much. But if the pump is in good shape, and can generate 6 or 8 in/hg relatively quickly then it won't have a problem with up to 4 in/hg of restriction.

Just food for thought.... If I don't catch ya sooner. Merry Christmas!

 

[agallant80]

Well this went off topic...look a squirrel

 

[alldodge]

Well this went off topic...look a squirrel

You sure about that? In post 4 you asked about adding a spin on filter, which then released the squirrel... so to speak

 

[Fun Times]

Just food for thought.... If I don't catch ya sooner. Merry Christmas!

Thanks Jason for all that and early Merry Christmas to you and everyone else.

Well apparently I seemed to be misinformed with Volvo wanting the Hg at 2. I swore I thought I read a Volvo manual recently that said the vacuum can't be above 2 in. Hg but of course I can't find it now. Plus I can recall our past west coast Volvo field rep saying 2 in. Hg. But all I can find in the Volvo manuals is if you're testing an electric fuel pump, the in. Hg range is 2 - 4 Hg. And if your testing a mechanical fuel pump like on a 3.0l, the vacuum range is 9 - 10 in. Hg.

Now to stay on topic, The Mercuiser gen 3 cool fuel manual says to not go above 2 in. Hg unless as a test you restrict the fuel supply using Merc's fuel shut-off tool to see if the low pressure pump has the ability to cause an inlet vacuum reading of 11 in. Hg or greater. Page 3A-2, http://www.boatinfo.no/lib/mercruise...ser40.html#/32

Well this went off topic...look a squirrel

Not really due to if you or someone else decides to add a filter before the gen 3 cool fuel module, you/their going to need to know most of this vacuum/restriction information before doing so. It just became a long discussion is all.

 

[agallant80]

Well it looks like I will just have to live with this POS. Adding in a fuel filter before does not seam like a good idea considering I will have to add in a booster pump. I will just keep a turkey baster and extra filters on the boat to suck out whatever is in the cool fuel module if I have water in the system.

 

[alldodge]

Don't know if there is enough room, but how hard would it be to add a drain? There is no pressure on the filter side, it's just a tank

 

[JustJason]

Well it looks like I will just have to live with this POS. Adding

There are of hundreds of thousands (maybe even millions, but I have no idea how many engines Mercury Marine sells a year) of these cool fuel modules all over the place. And not every one has problems. If you are having some kind of problem and the cool fuel module can not keep up with it, then really what you have is a fuel tank problem, not a CF problem. Ya need to figure out how water is getting into the tank.... Not worrying about how you filter it out. Under normal operating conditions the CF module will keep up, if its not, your tank is getting way to much water in it for another reason.

 

[agallant80]

There are of hundreds of thousands (maybe even millions, but I have no idea how many engines Mercury Marine sells a year) of these cool fuel modules all over the place. And not every one has problems. If you are having some kind of problem and the cool fuel module can not keep up with it, then really what you have is a fuel tank problem, not a CF problem. Ya need to figure out how water is getting into the tank.... Not worrying about how you filter it out. Under normal operating conditions the CF module will keep up, if its not, your tank is getting way to much water in it for another reason.

I don't have a problem, I just like to be prepared.

 

[jerryjerry05]

What you do is add a clear settlement bowl.
No filter just a catch bowl.
There would be little to no restriction.
The water would settle out and you just drain it when it shows.

I installed a water sep system in 88 when I got the boat.
21cc twin 85's
I have never found more than a few drops of water in all those years.

I installed a Racor with a clear bowl in my 32 with twins.
Both ran off the same tank.
I never had water in there either.

Remember the more you put in the system the harder the pump has to work.