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Old 10-02-2019, 09:12 AM   #1
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Diesel fuel tank configuration

...any info for 89 M Trader fuel tanks shape/ configuration? Setup appears to be sbord tank feeds 135 hp Lehman and port feeds genset...both returning to respective feed tanks. Tanks are purportedly 175 Usg ea. Like to know shape/ size and replacement options.
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Old 10-02-2019, 10:46 AM   #2
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Unless it is some aftermarket change made by a P.O. there is no way it would be set up like you describe. Look again, there must be a feed valve or switchover valve somewhere. 175 gallons would run my genset from new in 1978 until now, fuel would be pretty stale after all those years.

Replacement would be a big deal, Check this site for many threads about tank replacement. To start it off though, inspect your tank and take a fuel sample. Is there a bottom drain ? The P.O. may have replaced or reconditioned the tanks, can you ask him?

The switchover valve might be near the filter or filters (Raycors). Are you getting a lot of crud and water from your filters?

Don't be too fast to think tank replacement. The age of your boat puts it right on the edge of "Needing to be done" and "Already done". Don't jump into a $10,000 job.

Good luck, find the crossover valve, I guarantee that it is there!

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Old 10-02-2019, 12:04 PM   #3
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Welcome aboard. I agree that it is unlikely that one tank only feeds genset, however it is possible. It would not be optimal because not only will the fuel go stale for the genset but the side to side trim will be effected because your main engine will use much more fuel than the genset. I am going to replace one of my fuel tanks this winter just because it it a steel tank that is 32 years old. I have to pull an engine in order to get the tank replaced.
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Old 10-02-2019, 01:13 PM   #4
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My two penn'orth of advice on fuel.
Diesel doesn't go stale, I've seen engines left for 20 years and they cracked off just fine.
From experience with trucks, static engines and boats fuel systems over 40 years I would highly recommend that you go against convention and draw the fuel from the absolute bottom of the tank the same as a truck does.
You NEVER EVER see a truck tank with sludge or water build up in the bottom of the tank as you do on a boat.
Boat builders logic sometimes baffles me.
Draw the fuel from the very bottom of the tank and any impurities will be caught by the primary filter/water separator and the engine pre-filter. That's their function.
When building the new diesel tank for my boat I had it built in 316 Stainless Steel with a bright annealed (mirror) finish on the inside. 2 baffles with offset apertures and an inspection hatch over each baffle so I could access all sections of the tank if necessary, it cost a bit more but it was a case of fit it and forget it.
Peace of mind is priceless..
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Old 10-02-2019, 02:30 PM   #5
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If I remember correctly, for USCG inspected fuel tank, all openings have to be on the top. There can be no openings for lines etc anywhere else.
I always thought that instead of a flat bottom tank, that a lower bowl be built in that would allow all the water and sediment to settle there and then have another dip tube to allow you to draw all the muck out without using the main fuel lines.
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Old 10-02-2019, 02:43 PM   #6
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I have replaced a fuel tank in a previous boat and had them put the pickup about 1/4Ē off the bottom of the tank. I am going to replace a tank in my current boat this winter and will have the pickup as low as possible in the tank. I want any water and crud to be sucked out of the tank and go into the filters.
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Old 10-02-2019, 05:36 PM   #7
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Originally Posted by Whipper View Post
...any info for 89 M Trader fuel tanks shape/ configuration? Setup appears to be sbord tank feeds 135 hp Lehman and port feeds genset...both returning to respective feed tanks. Tanks are purportedly 175 Usg ea. Like to know shape/ size and replacement options.
Thks for feedback. I now see that both tanks are connect from fwd tank bottoms and can be gated off at each tank. Would logic suggest that the tanks balance or equalize by this route and still allow the genset to feed from the port tank with a direct supply thru its own Raycor and have a return line to this same tank. So reasonably the sbord tank draw being greater to feed the Lehman would always allow the port tank to slowly achieve balane thru the fwd connecting valved line.
I still have a sbord leak somewhere...if tank replacement is as cost prohibitive as suggested herein...would it be plausible to connect the genset to the Lehman sbord tank?
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Old 10-02-2019, 06:15 PM   #8
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I would not want to ignore a leaking fuel tank. Nor would I want to just leave it empty and only use one tank. As I said I am going to replace one of my fuel tanks this winter just because they are 32 year old steel tanks. If you do the work yourself it isnít as costly as some have quoted. I will have about $1500 in the crane, chain fall, trolly, etc. i will reuse all the misc equipment the following winter when I replace the second tank so it will cost about $750 per engine for the equipment to move my engines. The tank itself will cost about $2600 for a 1/4Ē 5052 aluminum tank.
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Old 11-18-2019, 04:23 PM   #9
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Ideally, any diesel tank should have a sump, but nearly the same effect can be had by angling the tanks bottom and placing the top mounted pickup at the bottom of the low side.
Itís a good idea to angle the top as well, Iíve seen many a tank rot from the top where water had pooled on the outside.
I like to hang the fuel tank, supported by flanges that mount to stringers or bulkheads rather than resting them on their bottoms. Air and water can then flow under the tank, decreasing corrosion threat there, as well as creating space for a sump.
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Old 12-02-2019, 08:55 PM   #10
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Hi Kapnd.
We all have our own ways of thinking and logic and I fully appreciate your thinking.
Not to be a smart ass but I've spent a large part of my working life in bulk tanker design/transport operations and bulk storage systems which has given me 'hands on' practical knowledge so I stand by my earlier post based on those years of experience.
Sometimes the exceptional becomes the accepted, this is the case with boat builders not drawing fuel from the very bottom (underneath) of the tank with lever type quick shut-off valve the same as a commercial truck has.
To be truthful I've also in the past fitted sumps on fuel tanks to collect/water/crud & draw off samples in the belief that boat builders knew best. They don't.
In each case fitting a sump helped relieve the symptoms but didn't eliminate the root cause of the problem.
As regards the fitting the fuel tanks, if the tank is fitted to the side of the boat I insulate the space between the hull and the fuel tank and place the tank on a sheet of 3/4 inch non-flammable expanded polyurethane, like yourself I use brackets to secure the tank firmly in place.
I also fully insulate the tank in the same material to eliminate any possibility of condensation but more importantly to stop it acting as an echo chamber thereby reducing engine room noise for comfort.

This has been practically time proven to work, eliminating the need for all those super-duper costly, and unnecessary, fuel cleaning/polishing systems by eliminating the root cause, not fixing the symptoms.
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Old 12-03-2019, 07:33 AM   #11
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Originally Posted by Irish Rambler View Post
My two penn'orth of advice on fuel.
Diesel doesn't go stale, I've seen engines left for 20 years and they cracked off just fine.
From experience with trucks, static engines and boats fuel systems over 40 years I would highly recommend that you go against convention and draw the fuel from the absolute bottom of the tank the same as a truck does.
You NEVER EVER see a truck tank with sludge or water build up in the bottom of the tank as you do on a boat.
Boat builders logic sometimes baffles me.
Draw the fuel from the very bottom of the tank and any impurities will be caught by the primary filter/water separator and the engine pre-filter. That's their function.
When building the new diesel tank for my boat I had it built in 316 Stainless Steel with a bright annealed (mirror) finish on the inside. 2 baffles with offset apertures and an inspection hatch over each baffle so I could access all sections of the tank if necessary, it cost a bit more but it was a case of fit it and forget it.
Peace of mind is priceless..

I concur. My original tanks in my 1979 49-ft MT were removed. They had alot of rust, sludge, etc inside. Brand new Stainless Steel barrel type tanks were installed in their place. Big rig tanks. Fuel outlet is at the bottom and the reasoning is as you stated. Happy with the results and no need for polishing, sludge cleanout or contaminated fuel in the past 10 years. Of course I went from 900 gallons of fuel storage to 300 gallons, but that is for another time. I do have a lot of engine room space now though!
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Old 12-03-2019, 09:10 AM   #12
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Hi Redhook98.
I was in the trucking business and I managed to get 2x 1,000 litre insurance 'write off' oblong truck tanks in stainless, I just had to blank off the fill aperture and re-site the filler to suit the deck fill pipe, having a single engine I wasn't stuck for space. The insulation/ soundproofing sure helps to reduce engine bay noise. Mine are tight up against the hull side and I sprayed expanding foam between the hull and the tank which, being adhesive also helped to secure it in place.
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Old 12-03-2019, 09:49 AM   #13
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Ideally, any diesel tank should have a sump, but nearly the same effect can be had by angling the tanks bottom and placing the top mounted pickup at the bottom of the low side..
This. Good builders have done it this way for a very long time.
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Old 12-03-2019, 11:44 AM   #14
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A small sump at the low point of the tank has the same flow characteristics and cleaning potential as a bottom outlet. On a big rig, if the threads or outlet hose leak, it goes onto the ground. In a boat, it goes into the bilge.

I had the tanks on my sailboat made with a sloped bottom and a small sump (about 1 pint) at the low point. The dip tube sucks even with the sump top, i.e., it will suck the tank dry other than that 1 pint. The slope encourages water and debris to travel into the sump over time. There is a 1 1/4 NPT plug directly above the sump, I can stick a tube down there and using the vacuum oil change pump suck all dirty fuel and debris out of the sump (even if the tank is full). The tanks sit on U channel welded to the bottom of the tank such that there is air circulation under the tank. The bottom of the U channel might eventually corrode from contact, but it can be cheaply replaced. I also made them weld the tank from the inside - that puts the relatively smooth weld bead inside. If not done that way you will have a very rough "back side" weld presented to the diesel and muck.

This are simple and cheap insurance, but doesn't sell boats at the show, so not typically done.
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Old 12-04-2019, 12:41 AM   #15
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The problem with exterior drain on the bottom in the US is that it is not ABYC and USCG compliant. A surveyor may flag the design and an insurance company may not agree to insure or worse reject a claim after a casualty.

Inspection plates are also out. When I had my tanks made they refused to install inspection ports. Not ABYC compliant. They did install a 1/2Ēport just above the low end of the tank for the equalization tube between tanks. This is allowed on a diesel but not a gas tank. All other holes in the tank had to be on the top.
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Old 12-06-2019, 07:10 AM   #16
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"A small sump at the low point of the tank has the same flow characteristics and cleaning potential as a bottom outlet. "

The problem with this is any water that collects is rusting the inside of the tank.

A better set up is a real sump of heavy wall metal , like the canister from an old style oil filter housing that screws into a flange in the tank bottom.

5 or 6 in diameter and nearly a foot deep.

This will catch and hold water and debris. The Navy uses this design with a stand pipe with a fitted cup that is left in the sump with straps to lift it.

A quick check , pull the bucket and empty it into a pail.

The delight is should the tank be filled with 1/2 water it can be bailed out with time.

The last bit of water might need a few hours to settle , but when you are done the tank is water free.

No pumps , no filters , no waste no valves , just time and gravity.

Although it takes a specific style of location and space below for the genuine sump.
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Old 12-06-2019, 08:13 AM   #17
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The problem with exterior drain on the bottom in the US is that it is not ABYC and USCG compliant. A surveyor may flag the design and an insurance company may not agree to insure or worse reject a claim after a casualty.

Inspection plates are also out. When I had my tanks made they refused to install inspection ports. Not ABYC compliant. They did install a 1/2”port just above the low end of the tank for the equalization tube between tanks. This is allowed on a diesel but not a gas tank. All other holes in the tank had to be on the top.



Not sure this is true for diesel tanks...it is for gasoline tanks ...but I could not find prohibitions to diesel tank openings below the fuel line for diesel. Unlike it clearly stating so for gasoline.




From ABYC...but I might have an outdated version.



"j. Drain valves on the filter(s) and fuel tank(s) shall be of the type which cannot be opened inadvertently,
or shall be installed in a manner to guard against inadvertent opening. All other outlets
for draining fuel from the system are prohibited."
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Old 12-06-2019, 01:57 PM   #18
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Not sure this is true for diesel tanks...it is for gasoline tanks ...but I could not find prohibitions to diesel tank openings below the fuel line for diesel. Unlike it clearly stating so for gasoline.




From ABYC...but I might have an outdated version.



"j. Drain valves on the filter(s) and fuel tank(s) shall be of the type which cannot be opened inadvertently,
or shall be installed in a manner to guard against inadvertent opening. All other outlets
for draining fuel from the system are prohibited."


I did not look it up. Thanks. Speedy tanks in NJ was insistent and would not yield. They used regulations as their basis. I called two other custom tank builders and had similar response. I really wanted the inspection hatches as I cannot access the tanks from the top.

The original steel tanks had inspection ports, but they were covered up by plywood and tile. No one ever knew they were there.
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Old 12-07-2019, 07:09 AM   #19
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"or shall be installed in a manner to guard against inadvertent opening. All other outlets
for draining fuel from the system are prohibited."

Inspection ports are not for draining fuel, they are only opened to service the empty tank.

Any drain valve should be fine with the addition of a metal plug .

Operating a gravity fed device like a heater or range is drawing fuel, not draining fuel.
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Old 12-07-2019, 05:31 PM   #20
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I did not look it up. Thanks. Speedy tanks in NJ was insistent and would not yield. They used regulations as their basis. I called two other custom tank builders and had similar response. I really wanted the inspection hatches as I cannot access the tanks from the top.

The original steel tanks had inspection ports, but they were covered up by plywood and tile. No one ever knew they were there.
I've just recently removed a leaking steel tank, so I find myself in the process of understanding what is required and/or recommended for diesel fuel tank construction and installation as I plan for replacement. Regarding your points, are these sources accurate? Is there another source that trumps these two?

Regarding inspection ports, ABYC indicates:

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And this is from 46 CFR 182.440 - Independent Fuel Tanks addresses fitting placement.

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