I think I have a miss matched fuel filter set up...

[Steve91T]

Hello everyone.

So a year and a half ago, I ran out of fuel with 300 gallons of diesel on board. I learned a lot about how my fuel system works that day. A few trips after I had an engine shut down while underway. Other engine wouldn’t make proper rpm either. Racors seemed clear. I changed the block mounted spin on filters and all was well. Seemed like the racors let crap by that the spin on filters caught and got clogged. This probably happened when I ran a tank dry sucking up junk at the bottom.

Fast forward to 2 months ago. Ran the boat 3 hrs to an anchorage and back and ran her hard. 1650 rpm with the current, 1800-2000 into it. (3 kt current). Ran awesome. Ran the generator the whole time.

5 weeks ago my dad went to the boat to drink my beer and run the engines. He ran all 3 at the dock for 15 minutes or so. All was well.

A few days ago we load the kids up and go to the boat with plans to go anchor for the night. We got to the boat to find the fridge had died which was absolutely disgusting along with the fresh water pump overheating. Instead of anchoring, we went for a quick cruise to the ocean and back. I found the starboard engine wouldn’t go past 1400 rpm and the port, 1600. No smoke, no signs of lugging. Acted like they weren’t getting enough fuel. The bottom and running gear was dirty but the engines didn’t feel labored. And running both at 1300 the speed was as expected; about 6.5 kts ish. Also 45 minutes into the trip, the generator quit. Now I don’t know why it quit, all I know is it started and ran at the dock for 15 minutes with a load with no problems. After the trip both engines hit 2800 ish rpm in neutral.

I had the bottom cleaned that day. Water outlet flow for the generator before and after was identical.

So I checked the racors and they are dark but zero debris at all. I’m thinking they are letting things by that the block mounted filters are catching. I feel like it should be the other way around. Racors are easy to change and can actually be done while underway. Block mounted filters are a chore.

Thoughts?


Engines are Lehman 225’s and yes, I’ll call Brian in the morning. Still, a diesel is a diesel and I wanted to hear other experiences and opinions.

Thanks again.

 

[Russell Clifton]

Perhaps the micro rating for the Racor's is larger than the secondary filters so the bigger stuff is getting to the secondary filters? Racor's do come in optional micron sizes.

 

[Yachtman]

Sounds like an afternoon in one of our 60+ yr old British cars!

 

[SoWhat]

Both engines won't reach max rpm at the same time? Highly unusual. I am assuming you have 2 tanks, probably connected. Each tank should go to a racor. Each racor to the fuel pump, each fuel pump to the cav filters on the engine. Most boats would have valving to allow feeding both engines from one or the other tank or both. Typically you would run port engine from port tank.

So the first question is have you checked position of all valves?
Second question is have you checked fuel tank vents? The little screens corrode and can block the vent. Remove the screens.
Third question on filters has already been addressed, What size are in primaries, what size in secondaries. If you are buying fuel from busy marina you are probably getting good clean fuel. (I add biobor to be on the safe side.) The WIX 33166 are 10 micron so typically you would use 20 micron in racors. 30's would be OK.

I might crack all the fittings while running and then retighten to make sure there are no air leaks. I would also stick a borescope down the tank fill tube to check the bottom of each tank. They should be clean and shiny.

I would also eliminate drivetrain issues. While in ER, I would turn each shaft by hand. They should be stiff but move freely. If not the packing may be too tight or the strut bearings are going. Would be unusual for both to go at once.

If you discover you are running both engines from one tank, then there is a restriction. Blow the lline out with compressed air. If you are running from both tanks, you have a mystery on your hands.

 

[Comodave]

I run 10 microns in the Racors and the secondaries are not labeled but it seems that they are around 7 micron. I see no reason to run 30 microns in the Racors although many will argue that you must have larger microns in the Racors. I want the Racors to trap everything that will get trapped in the secondaries. As you noted the Racors are much easier to change than the secondaries so why not trap the crap there? I also put a small LED light behind the bowls of the Racors so I can easily see what is or isn’t in them. It is much more effective than a flashlight since the bowl is backlit rather lighting the bowl from the front. Another thing I did on the port side and will do on the starboard side this winter is add a Racor priming pump in the Racor filter. It makes priming simple, even for the secondaries. I change the filters and push the priming button for a couple of seconds and the secondaries are full. In the first photo the priming pump is the black section in the middle of the pump. The second photo shows the backlit bowl. The nice thing about the Racor priming pump is that it doesn’t add more connections to cause leaks and it doesn’t take more real estate to mount a pump.

 

[Steve91T]

Both engines won't reach max rpm at the same time? Highly unusual. I am assuming you have 2 tanks, probably connected. Each tank should go to a racor. Each racor to the fuel pump, each fuel pump to the cav filters on the engine. Most boats would have valving to allow feeding both engines from one or the other tank or both. Typically you would run port engine from port tank.

So the first question is have you checked position of all valves?
Second question is have you checked fuel tank vents? The little screens corrode and can block the vent. Remove the screens.
Third question on filters has already been addressed, What size are in primaries, what size in secondaries. If you are buying fuel from busy marina you are probably getting good clean fuel. (I add biobor to be on the safe side.) The WIX 33166 are 10 micron so typically you would use 20 micron in racors. 30's would be OK.

I might crack all the fittings while running and then retighten to make sure there are no air leaks. I would also stick a borescope down the tank fill tube to check the bottom of each tank. They should be clean and shiny.

I would also eliminate drivetrain issues. While in ER, I would turn each shaft by hand. They should be stiff but move freely. If not the packing may be too tight or the strut bearings are going. Would be unusual for both to go at once.

If you discover you are running both engines from one tank, then there is a restriction. Blow the lline out with compressed air. If you are running from both tanks, you have a mystery on your hands.

To answer a couple of your questions...

Left and right tanks go to racors then into a manifold. From there they go to the three engines. All three can pull from the left or right tank. Generator and port engine return to the port tank. The starboard engine returns to starboard tank. I had the valves open so they were pulling from both tanks.

Another thing I noticed....when we left, both tanks were half full 75 gallons each and even, more of less. When we got back after the 2 hr trip, the starboard tank was empty and all the fuel transfers to the port tank. This actually isn’t that uncommon to this boat, but I was surprised to see so much fuel moved from one tank to another so quickly.

The other thing that’s odd is during that 1.5-2 hr trip, nothing changed. 1400 rpm starboard and 1600 port. I’d run then at 1300 and every once in a while push the throttles to the stop and that was always the result.

That’s why the only thing I can think of is clogged block filters.

Something is up, just not sure what it is yet.

 

[SoWhat]

Sounds like a blockage in your port feed line. The 3/8" line from the starboard tank just isn't supplying enough volume for 2 engines under load. Once you are back at the dock, no load so you regain rpm's.

I would blow the port line out, tank to engine.

Certainly check your filters. It won't do any harm. Pull the pleats apart and check carefully inspect them. If they are in fact plugged up then you have a tank cleaning task in front of you.

I think it is safer to run each engine off each respective tank to avoid any potential cross contamination problems. Genny needs it's own Racor and a system where you alternate which tank it draws from on each trip.

 

[kapnd]

Vacuum gauges are a valuable tool for troubleshooting fuel supply problems.
Sounds like the root of the problem may be in the tanks themselves.
Don’t forget to check the vents!

 

[O C Diver]

Think you need to do some replumbing. As mentioned the Racors should be for each engine and generator, with manifold plumbing before them.

The way it's currently plumbed, which ever tank has the lowest resistance (vacuum requirement to draw fuel) will be the one the fuel comes from and it all has to go through that one Racor. If you have an air space in that one Racor or the fuel line feeding it, no fuel may be coming from that side.

Ted

 

[Steve91T]

Thanks everyone. I agree it needs to be re plumed. The biggest problem is I can’t run off one tank for long because the return from each engine goes to its respective tank. So shutting off a tank will quickly transfer to the other.

I do have a transfer pump, but it isn’t filtered. It would be really nice to have a filter on it so I can at least do some filtering while I transfer fuel.

I do have a priming pump that pulls from the starboard tank to the manifold and pressurized the system. It works well.

Here’s a picture that I found of the manifold and racors on the back wall. It’s a terrible zoomed in pic, it it’s all I have right now.

So with all that being said, what could have changed from the last time I ran the boat 2 months ago? I had gotten fresh diesel and also put in fuel injector cleaner and ran her for 3 hrs each way.

I don’t know how the filters could all get clogged at the same time while sitting. And I think it’s unlikely that both fuel tank vents clogged at the same time.

I definitely need to get those vacuum gauge t handles...that would take a lot of guess work out. I might get them and install them before touching anything just to see what I see.