Fuel Polishing with my current system

[MGRodems]

I want to install a fuel polishing system in my engine room. When I looked for space to mount the components, I realized that I need to first diagram the flow I already have. I have only had the boat for one season, so I had not yet gotten to documenting this system.

The attached diagram is what I inherited and currently have installed. I am a bit surprised by the design. It appears that there are two paths to the engine and genset that each go through their own filter. The shut off valves have all been in the open position since I bought the boat.

It appears that the shutoff valves are there to allow fuel filter cleanings, since there is a shutoff before and after both filters.

I have a few questions:
1. Is there any merit to this configuration? It appears that if one filter is clogged I would not know it until they both get clogged.
2. Why does the genset fuel return go through the engine before it can get to the fuel tank? With the genset running and the engine not running - it appears that the excess fuel cannot get back to the tank.
3. How would you set up the flow to have a fuel polisher built into the system?

[valhalla360]

Originally Posted by MGRodems

I want to install a fuel polishing system in my engine room. When I looked for space to mount the components, I realized that I need to first diagram the flow I already have. I have only had the boat for one season, so I had not yet gotten to documenting this system.

The attached diagram is what I inherited and currently have installed. I am a bit surprised by the design. It appears that there are two paths to the engine and genset that each go through their own filter. The shut off valves have all been in the open position since I bought the boat.

It appears that the shutoff valves are there to allow fuel filter cleanings, since there is a shutoff before and after both filters.

I have a few questions:
1. Is there any merit to this configuration? It appears that if one filter is clogged I would not know it until they both get clogged.
2. Why does the genset fuel return go through the engine before it can get to the fuel tank? With the genset running and the engine not running - it appears that the excess fuel cannot get back to the tank.
3. How would you set up the flow to have a fuel polisher built into the system?

1) The first two filters (downstream from the fuel tank) appear to be set up so you can replace filters under way. Normally, the valves to the 1st filter would be open and the 2nd closed. If the 1st filter you are running on starts to get clogged, you open the valves to the 2nd filter then close the valves to the 1st filter. Now there is no flow to the 1st filter while the engine keeps chugging along on the fresh 2nd filter. Change out the 1st filter and you have a spare fresh filter ready to go. A nice option to keep you going if you run into fuel problems rather than having to shut down bouncing in a rough sea while you replace a single filter.

2) Are you sure the genset return line actually goes back to the main inlet path (downstream of the fuel pump)? I would have expected it to either go straight to the tank or "T" up with the main engine return and then back to the tank.

3) How big is the tank and how easy it it to get to the various parts? I built a simple portable one years ago. Just a fuel pump and cheap in line filter, some fuel hose and some long wires. Installed the pump and filter in line on the hose. Then disconnected the hose from the tank and plugged in my polishing system onto the now open tank outlet. Then ran the hose back to the fuel fill. Connected the pump up to the battery and let her run for an hour or so (or till the filter got clogged...and then replaced the filter). But this was on a boat with 2 - 20gal tanks and I had already drained and cleaned them shortly after buying the boat so wasn't dealing with anything horrible.

[boatpoker]

The genset line (and any other engine line) is supposed to return fuel to the same tank it was drawn from.

[s/v Jedi]

Here’s the “gold standard” setup I designed (stole from others ) in 2006. It has been installed by countless cruisers and functioned flawlessly for more than 15 years now

The big highlights are the fuel polishing function, the effortless priming/bleeding and boost (force fuel through clogged filters in emergency), fuel transfer etc.

[Statistical]

1) It is a common setup. It lets you change a filter with the engine running. Useful if you find chop has stired up junk and clogged your filter and you don't want to be bobbing around fraking with filters without propulsion. However normally it is used one open and one closed. If you have both filters on at the same time they likely will get clogged at the same time making it pointless. Sometimes instead of two separate valves it is just a three way valve. So it can be filter A, filter B, or off. If you don't like it or need it you can go to a separate filter for the engines and gen or even just a single filter for both. Personally dual filters is a bit of peace of mind. If means a clogged filter won't leave you stranded.

2) That is weird. I see no good reason for it to be piped like that. Some possibilities would be someone didn't know what they were doing, they did know what they were doing but got confused installing it and ran the lines wrong, or you traced it wrong.

I would double check your configuration and if the diagram is correct I would run the generator return either directly back to the tank or to a t connection that joins engine and gen returns and goes back to the tank.

3) Polisher can be as simple or complex as you want it to be. You can either have it be a separate loop (line from tank to filter to pump back to tank) or modify this loop to have a path that goes through the filters and returns back to the tank.

[Russ]

Suggest you Google "Cap'n Will's fuel polishing system" as seen below:

Captn Wil's Fuel Polishing System: Trawlers & Trawlering How To

I have used the exact install for 20 years. The Gulf F-1 is the key. Works with Bounty Paper towels as a filter and they are CHEAP compared to feeding a RACOR 500 filter unit

[MJH]

Originally Posted by MGRodems

I want to install a fuel polishing system in my engine room. When I looked for space to mount the components, I realized that I need to first diagram the flow I already have. I have only had the boat for one season, so I had not yet gotten to documenting this system.

The attached diagram is what I inherited and currently have installed. I am a bit surprised by the design. It appears that there are two paths to the engine and genset that each go through their own filter. The shut off valves have all been in the open position since I bought the boat.

It appears that the shutoff valves are there to allow fuel filter cleanings, since there is a shutoff before and after both filters.

I have a few questions:
1. Is there any merit to this configuration? It appears that if one filter is clogged I would not know it until they both get clogged.
2. Why does the genset fuel return go through the engine before it can get to the fuel tank? With the genset running and the engine not running - it appears that the excess fuel cannot get back to the tank.
3. How would you set up the flow to have a fuel polisher built into the system?

I would think the fuel return from the genset would go back to the tank like the engine does. Plus you have two flows coming togther in the opposite direction.

~ ~ _/) ~ ~ MJH

[MGRodems]

Great replies so far.

I was also wondering why both filters were activated at the same time when I purchased the boat in 2020. I did not change anything and had no issues on a summer-long trip through 4 Great Lakes last year. I was working on all of the other systems before I got to this one.

I was confounded when I saw the genset return line running the flow INTO the engine. I assume the PO changed the original design. The parallel routes for the filters makes sense, but not if both are on at the same time, which was the setting I inherited.

My first step is to reroute the genset return to join the engine return to the tank. That is a no-brainer.

My second change might be to run the fuel from the tank through the two filters in series vs parallel and to a tee that sends it either to the engine and genset or back to the tank with shutoff valves controlling which way it goes. The pump would drive the polishing of fuel. The valves in the opposite setting will allow running the engine and the genset.

I have attached the diagram. Sorry it is sloppy. The pump doesn't run while using the engine or genset. When polishing, I would turn both valves to direct the flow back to the tank and turn on the pump. Reverse the valves to direct the fuel to the engine and genset when polishing is complete.

In this setup, I am using only two of the four valves I have. Would there be a benefit to putting one before the first filter to keep the fuel in the line when cleaning the filters?

Alternatively, should I keep the parallel filtration system I had before, and run the fuel through one or the other but not both?

Series or parallel? I never thought this choice would apply to fuel. Interesting!

[sinnerman]

Your current installation has two switchable filters primary/secondary to allow moving over to the alternate filter when the first filter clogs.

The primary filter is the one with the vacuum gauge on it. If it starts showing a vacuum (pressure drop across the filter) the filter is becoming clogged.

This setup allows you to keep motoring when the main filter clogs by switching filters, instead of having to drift along while you change the filter at sea at the worst possible moment.

It is not a "polishing system" . Only fuel flow back to the tank is unused fuel form the fuel injectors on the engine(s).

A polishing system is like a pool filter in a home. It sucks fuel from the LOWEST part of the tank where the water/algae/ sludge collects, circulates it through a water separator/filter and sends it back to the tank. It would have its own separate electric (fuel) pump and water separator/filter.

You could "convert " your system to a " polishing" system by adding an additional return line to the fuel tank downstream of the fuel pump with an in-line closure valve and a way to turn the pump ON when the engine is not running. You would open the inline valve , turn ON the fuel pump and let it circulate. Close the inline valve for normal engine operation. I would not run with the inline valve open when the engine is operating as you may starve the engine of fuel..

I think this would be overkill as you have two filters, one as a backup. If you have problem with the filters clogging regularly, it is time to clean the tank, add biocide or switch fuel suppliers.

Cheers

cheers

[Statistical]

Originally Posted by MGRodems

Series or parallel? I never thought this choice would apply to fuel. Interesting!

I would stick with parallel. If you are ever bobbing around with a dead engine because you have a clogged filter you will be thinking the same thing "I really wish I had a parallel filter and could get underway by flipping a valve". Just avoid the mistake of the prior owner and only use one filter at a time. Having both open is pointless you might as well just go to a single filter.

The pump doesn't run while using the engine or genset.

This is probably not correct I say probably only because there are so many potential edge cases. The lift/boost pump is designed to ensure the pump on the generator/engine doesn't have to pull the fuel all the way from the tank. It is always used. If you add a fuel polishing loop it would be used for that too but it is used regardless.

[s/v Jedi]

Please check the diagram I posted above. The lift pump that is mounted on the engine and genset lifts fuel from the tank and through the primary filter as well as the engine mounted secondary filter, sending it to the injector pump.

The fuel polishing is a separate circuit using a separate filter and pump. You normally use a courser filter here, like 10 or 30 micron. The output T’s into the fuel return.

My diagram has a second pump which pressurizes the primary filters, pushing fuel at 6psi pressure to the engine lift pump. This has several big advantages:

- When you have an air leak, it stops the engine and is difficult to find. With the boost pump, the air leak becomes a small fuel leak: easy to find and the engine keeps running.

- When you need to bleed the engine you just run the boost pump and start the engine. No more tools needed and no mess.

- When your filters plug up it’s always at a bad time. Start the boost pump and fix it later (the pump will get the fuel through the filters).

[David B]

Originally Posted by MGRodems

I want to install a fuel polishing system in my engine room. When I looked for space to mount the components, I realized that I need to first diagram the flow I already have. I have only had the boat for one season, so I had not yet gotten to documenting this system.

The attached diagram is what I inherited and currently have installed. I am a bit surprised by the design. It appears that there are two paths to the engine and genset that each go through their own filter. The shut off valves have all been in the open position since I bought the boat.

It appears that the shutoff valves are there to allow fuel filter cleanings, since there is a shutoff before and after both filters.

I have a few questions:
1. Is there any merit to this configuration? It appears that if one filter is clogged I would not know it until they both get clogged.
2. Why does the genset fuel return go through the engine before it can get to the fuel tank? With the genset running and the engine not running - it appears that the excess fuel cannot get back to the tank.
3. How would you set up the flow to have a fuel polisher built into the system?

I like to keep things simple and obvious.
Given that most monohull yachts have a single fuel tank, here is the arrangement we have:

GENERATOR
Independent valved feed from fuel tank to generator filter.
Valve either side of filter, then on to generator.
Independent return from generator to fuel tank.

ENGINE
Independent valved feed from fuel tank to tee
Pair of fuel filters fed by tee, and re-combined on outlets by tee, then on to engine.
Both filters valved either side
Independent return from engine to fuel tank.

By the term 'fuel polishing', I understand an independent feed, filtering, and return system - whether anything is running or not, it works by an independent electric fuel pump. So again, a simple, independent system, with another (larger - dependent of flow-rate of pump) independent supply and return to the tank.