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Old 02-09-2019, 04:13 PM   #1
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Fuel System Redesign

Embarked this morning on a bit of a flight of fancy...

My KK42 is at a new marina as of Tuesday of this week, that is another story in another thread... that I need to update.

This morning, I decided to layout a new fuel system, that I've been thinking about, since the original system in her now is suspect (no issues, just old and failed once on PO already). This is a project that I probably wouldn't start until April at the earliest.

Goals (some conflict with others as expected, therefore compromises will have to be made).
  1. Simplicity: Less stuff is less to break. I want the minimum components that would provide safe and reliable delivery.
  2. Electric priming. To me should have been standard equipment. The trouble everyone has bleeding these dang things, and for a few hundred bucks that can go away. And provide safety as well? Seems a no brainer to me. Plus, swapping in a spare is easy.
  3. Ability to move fuel from one tank to another: I consider this a safety and convenience feature. Adjust trim, polish a tank, move all bad fuel to one tank, etc. The boat has 7-800 gallon capacity, and will be coastal cruising for the next 5-10 years, and then maybe offshore after that.
  4. Fuel Polishing: In the design, it should be able to polish. Not a massive polishing system, but one that with regular use could get the worst out, and not require drilling more holes with more valves in tanks that could fail.

Possible controversial design ideas and related questions:
  1. No sight tubes (or should I?). If I'm offshore, and the electronic sensors fail, for one I should have already done the math to assure we'd make it with reserves, and with some rechecking of math and even running a tank to nothing I have electric prime to move to the other tank and continue.
  2. Inspection Plates: Could I replace them with plexiglass (fuel resistant?)? Backup fuel level for removing sight tubes.
  3. Remove on engine lift pump: Engine driven lift pumps have a small but real risk of breaking in a way that could strand you. With electric pump and spare plus four different spare battery sets I see this as an obvious choice for reliability.
  4. No shutoff valves at tank for returns. I'm not sure why they are needed, but I'm probably being an idiot here and someone will point out my errors.
  5. Do I need the check valve in the return line before the polishing system dumps fuel in the line? My feeling is that I don't want to accidentally push fuel backwards into the injection pump (not sure it can or not...).

Please feel free to point out the errors of my ways, there may be many. I may have forgotten an entire concept. It's just a flight of fancy for now, as there are a lot of other things I have to do first before I even touch the fuel system.
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Old 02-09-2019, 04:33 PM   #2
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Only comments I will make is one reason that many folk have for keeping a mechanical fuel pump is if the electrical system fails then the electric fuel pumps will also fail.
With an all mechanical system if you can get fuel to the engine and get the engine started, it will run. THat also goes for the shutdown or fuel cut off valve. If power is needed to run that is also seen as a big disadvantage.

The electric priming pumps - sure.
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Old 02-09-2019, 04:37 PM   #3
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Well, if you're looking for opinions:

Not a fan of shared fuel source for generator and engine.
Electric fuel pumps fail also. If you want to improve reliability, treat it as a raw water pump with time scheduled maintenance or replacement as opposed to waiting for it to fail.
If you want simplicity and reliability, draw fuel for engine and generator from the one same tank with only a fuel shutoff valves. Set up a simple transfer / polishing system that allows you to draw from either tank and return either tank. If you keep the suction manifold low, you could equalize the tanks with gravity siphon effect if your pump failed.

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Old 02-09-2019, 04:44 PM   #4
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I’d keep the sight tubes. You can’t have a more reliable level indicator. Just have ball valves so you can shut them off at the tank. Why replace the inspection ports? Are your tanks fiberglass or steel?
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Old 02-09-2019, 04:50 PM   #5
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I believe they are fiberglass.

Replace inspection ports with see through material just for the added ability to peer inside and gauge levels from 40-60% or maybe even wider.

Remove sight tubes because even though they are reliable, they are redundant, add valves, and in theory are a possible diesel bilge fill hazard. I want super simple.
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Old 02-09-2019, 04:52 PM   #6
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Good point, batteries do run down. Fuel pump would keep going. Maybe it stays.
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Old 02-09-2019, 04:58 PM   #7
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Nothing unreliable about sight tubes. Just leave them valved out unless checking level.
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Old 02-09-2019, 05:06 PM   #8
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If it matters, I have to replace my sight tubes. There is a distinct lack of being able to see through them. That annoyance might be coloring my view of them.
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Old 02-10-2019, 11:08 AM   #9
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I just modified my fuel system.

Added a Webasco electrical fuel pump to the Generator Racor 500 circuit.

Fuel is supplied via the existing Grand Banks fuel manifold. The polishing pump was put inline before the WAY oversized generator Raycor 500.

Simple 1/4 mini valves from NAPA allow me to isolate the polishing circuit, and return fuel to either tank or back to the manifold.

With existing tank and manifolds I can do about anything. Polish while underway, with genset running, etc.

I expect it to move at least 30gph. I have an isolated squeeze ball circuit on each filter to prime filters.

It is all hard plumbed, is simple to understand, and can be reconfigured in the boonies to do anything, including emptying the tanks to drums.
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Old 02-10-2019, 11:52 AM   #10
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Do a magnet test on the tanks, they may be coated. See thru inspection ports on fuel tanks might not be legal, your surveyor can probable tell you. I’m also a fan of sight glasses with shut off valves.
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Old 02-10-2019, 12:09 PM   #11
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We replaced the tubing several years ago and used Tyson F-4040-A. I’ll probably replace it again in a couple of years. I’m not sure there is a material other than glass that doesn’t cloud up over time.

https://www.usplastic.com/catalog/it...x?itemid=23487
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Old 02-10-2019, 01:30 PM   #12
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Change out your mechanical lift pump on PM basis as suggested by OC, Clectric etc. I changed out one and after 13 years it was doing fine, but just time. Sure, if you want put in an electric but valve it such that it is ready to go if needed but off line most of time.

My wire braided “clear” sight tubes remain viewable after 14 years. BTW, lots of ways to hook up a “polishing” system. Suggest you keep your primary fuel delivery system as simple as possible and start out with newly cleaned tanks. Maybe a “polishing” system would then be the proverbial solution for a problem that doesn’t exist.
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Old 02-10-2019, 02:46 PM   #13
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Fuel system

Bridaus, -- does that mean you name is Brian ?

Glad to meet a fellow KK-42 owner & also I understand your a pilot - well so am I. We pilots, often think alike, as pilots, we like back up systems & to keep things simple. So I understand some of your thought process.

First - your diagram even though I understand it is a rough sketch, does not reflect the true KK-42 fuel system design. The supply lines come off the bottom of the fuel tanks (not the top as you show) as a gravity feed to the mechanical fuel pump, as I recall, unless you have replacement tanks that are not OE, & it was changed.

Next - any fuel polishing system you add needs to NOT impact the main fuel feed system at all. - it needs to be completely separate.

YES - Adding a fuel primer circuit is a good idea, but must be designed & set up properly or can cause issues & it can also work, if designed properly, to be a good back up to your mechanical fuel pump should the need arise. See my priming system in picture below.

Adding a clear fuel window at your clean out access port is Not a good idea - the more light that gets in there the more algae growth there will be. Also not Coast Guard legal, so not a good idea & not particularly useful as where you need to see is down at the very bottom of the tank, so half way up the sides is not useful for your perceived fuel inspection of what the fuel looks like, mid tank fuel clarity is not what you need to know. So it does not give you the information you think it would.

I have now been told by "SEALIFE" that to the best of his knowledge all KK-42's through hull #65 have solid drop in 1/2" thick fiberglass tanks. No steel at all till after Hull # 65. This is great news for the earlier models !

In the KK-42 Blueprints it says, in error, that the tanks are 400 gal each, for 800 gal total. I have confirmed with KK in Stuart , Fl. & Also myself personally that is an error / oversight, as we have an 1982 KK-42 # 35 & drained our tanks 100% that the OE tank factory feeds would permit to flow fuel & refilled them while measuring what it took to refill them & they have an OE tank actual capacity of just couple gallons over 350 gal each, which turned out to be a usable fuel capacity of just a few gallons over 700 gal. total, usable fuel. -- so capacity of OE fuel tanks is 700 US Gallons.

Yes, there was a little fuel still left in the tanks, but it is not usable fuel & your sucking air & your engine would die of fuel starvation. We did not measure how much that was, but since it is unusable, & this extra fuel weight was not critical on a boat like it is in aircraft & the engine would suck air & stall, we felt it was a moot point. If you're a pilot & you have flown Piper Aircraft, you should be very familiar with usable fuel & unusable fuel & that they are different numbers, compared to total fuel weight on board & unusable fuel is included in the base weight of the aircraft or vessel. -- So 700 Gallons is your fuel capacity.

Next question - (if you have one, many do) -- do you have a bow thruster ? & next, is your bow thruster a hydraulic or electric unit ? -- standard option was a 5 HP Hydraulic bow thruster unit that has a hydraulic pump drive off the main engine front crankshaft with a belt drive pump. Hydraulic tank is typically located up front of the engine room on the front starboard wall, opposite side from the forward ER electrical panel. Near where the fresh air intake is. -- See picture below.
Why I mention this, if you don't have the hydraulic tank mounted there at front of ER on front wall, that is a perfect place to put your dual RACOR fuel filters !

Looking at the KK-42 Factory fuel tank specs blueprint diagram there are cross connection bottom tube or tubes & one top return connecting tube. Factory OE has on/off valves at each tank connection. -- be that the sight glass at top & bottom, return crossover lines, & supply lines & cross feed level lines, etc..

The OE system is proven & simple. Everything is located at the front ER bulkhead / wall between the two tanks. What you do from there fuel plumbing wise & adding in DUAL RACOR filters, etc. is up to you, but please, don't fix what is not broken. Love to hear how you set it up.
I do not recommend you get rid of the sight tubes fuel level measuring system, Replacing the hose with proper clear reinforced proper hose is quick & easy & not a messy job at all. If your concerned about a leak there, Just turn off the valves when level readings are not needed to be made, as it is reliable & accurate. Much more accurate than any electric fuel level sensor.


See my KK-42 Fuel Filter & fuel tank below. NOTE: fuel valve & priming pump off to the side. Ignore the red hose - I was rerouting the hydronic heating system at time of picture was taken last year. So kind of messy in the ER, but shows the Fuel Filtering system I set up. I decided after having a bad experience on a friends boat down in Mexico, the RACOR 500's were to small for my taste, went with the 1000's. For me, More filter capacity the better.


Since we are talking about ER's, I also moved my water heater to the back corner of the ER & also moved my raw water intake valve & through hull & strainer to the front starboard part of ER so it was accessible much more easily from the galley access hatch, without having to lift the salon floor hatches to get to it.

From one pilot to another, Good luck with your project.

Alfa Mike


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Old 02-10-2019, 02:59 PM   #14
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Polishing: My polishing setup lives in a 5 gal bucket. I can use it for polishing (rarely) or to empty a leaking tank if needed. It has elec pump, spare racor, and 20 ft output hose to run fuel back into fuel fill.

Filtering: Your design runs the fuel through 3 filters. You only need 2. The Racor dual filter with single valve/double manifold allows you to switch filters on the fly giving you redundancy (and you really don't want to change filters in a sea way.) I might be reading your diagram wrong.

You could build a more complex custom system that puts left tank through left filter, right tank through right filter, or both tanks through either filter, with corresponding return valves, but that's overkill.

Fuel Pumps: Mech pumps are reliable. I keep a spare on board. I could use my polishing pump if needed. Priming is a quick process and I rarely do it so I just replaced all hoses during my rebuild.

For simplicity and redundancy you can't beat the dual racors.
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Old 02-10-2019, 03:35 PM   #15
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There is always an exception, but to the best of my knowledge all kk42 through hull #65 have solid drop in fiberglass tanks. No steel at all, even the inspection ports support this. The 700 gallons total is correct.
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Old 02-10-2019, 03:39 PM   #16
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Scott: Have you heard of any failures with the fiberglass tanks? I know from personnel experience that the steel tanks have had their issues.
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Old 02-10-2019, 03:59 PM   #17
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No, I don’t know of any hulls before #66 having tanks replaced. I replaced the fittings on mine and they were easily 1/2” thick.
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Old 02-11-2019, 10:47 AM   #18
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Quote:
Originally Posted by alfamike View Post
Bridaus, -- does that mean you name is Brian ?
Glad to meet a fellow KK-42 owner & also I understand your a pilot - well so am I. We pilots, often think alike, as pilots, we like back up systems & to keep things simple. So I understand some of your thought process.
Yes, Brian, very nice to meet you.


Quote:
Originally Posted by alfamike View Post
First - your diagram even though I understand it is a rough sketch, does not reflect the true KK-42 fuel system design. The supply lines come off the bottom of the fuel tanks (not the top as you show) as a gravity feed to the mechanical fuel pump, as I recall, unless you have replacement tanks that are not OE, & it was changed.
It's just my bad drawing, the supply comes from the bottom. Tanks are OE.


Quote:
Originally Posted by alfamike View Post
Next - any fuel polishing system you add needs to NOT impact the main fuel feed system at all. - it needs to be completely separate.

YES - Adding a fuel primer circuit is a good idea, but must be designed & set up properly or can cause issues & it can also work, if designed properly, to be a good back up to your mechanical fuel pump should the need arise. See my priming system in picture below.
Yes, I want the electric pump inline so that it can be used in a pinch. This is just like an small airplane. They have an on engine pump and an electric fuel pump. If on engine dies, you turn on the electric. Redundancy.

Quote:
Originally Posted by alfamike View Post
Adding a clear fuel window at your clean out access port is Not a good idea - the more light that gets in there the more algae growth there will be. Also not Coast Guard legal, so not a good idea & not particularly useful as where you need to see is down at the very bottom of the tank, so half way up the sides is not useful for your perceived fuel inspection of what the fuel looks like, mid tank fuel clarity is not what you need to know. So it does not give you the information you think it would.
Good point about light/algae growth, although you could put a cover over it. It was just an idea.

Your points about usable = 350 per side, good to know. I figured it wasn't the full 400, but quite a difference, eh?

Quote:
Originally Posted by alfamike View Post
Next question - (if you have one, many do) -- do you have a bow thruster ? & next, is your bow thruster a hydraulic or electric unit ? -- standard option was a 5 HP Hydraulic bow thruster unit that has a hydraulic pump drive off the main engine front crankshaft with a belt drive pump. Hydraulic tank is typically located up front of the engine room on the front starboard wall, opposite side from the forward ER electrical panel. Near where the fresh air intake is. -- See picture below.
Why I mention this, if you don't have the hydraulic tank mounted there at front of ER on front wall, that is a perfect place to put your dual RACOR fuel filters !

From one pilot to another, Good luck with your project.

Alfa Mike
Electric bow thruster.

Thanks for all the info, and the luck. I'll take any I can get.
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Old 02-11-2019, 10:55 AM   #19
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Next time I'm at the boat, I'm going to take a picture of the rats nest of valves and lines and etc. that have been bodged on over the years.

Changes based on feedback:
  1. I'll keep the on engine pump. The value in it's mechanical operation exceeds the failure potential.
  2. Inspection plates: I'll leave them alone. It was a dreamy idea.
  3. I'm on the fence with sight tubes still. I'm a minimalist.


Questions I still have:

Is the check valve needed to avoid fuel pushing backwards through injection pump when polishing?
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Old 02-11-2019, 12:36 PM   #20
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Most of the Walbro pumps are pass through designs. I have mine mounted in line and only turn on when I want to move fuel from tank to tank, polish, or prime. Leave everything else in place. Exactly what you have in mind. For less than $150 (Pump, 3 way valve, and a few fittings). my system is now very flexible and does exactly what I want it to do. Keep it simple..
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