Yesterday, during spring commissioning of my Universal M25-XPB engine, I did my first change of the primary and secondary filters. Previously, I had always had the yard do it. I followed step-by-step instructions from a sailing YouTube sailing blogger I follow who has, or so I thought, sound maintenance advice. Following his recommendation, I pre-filled both the new primary and secondary filters with fresh, clean diesel before I installed them. I then cycled the glow plug a few times to prime the engine and started it up. The engine started and ran flawlessly and I let it warm up at idle for about half an hour. Only after getting home and carefully rereading my Nigel Calder book on marine diesel maintenance, did I see where he advises to never pre-fill the secondary filter as it could introduce contaminants into the system downstream from the filters. I think I am ok because I made sure my new fuel was clean when I pre-filled and the engine was running like a top after. Did I (hopefully) dodge a bullet? Is there anything I should do after the fact? I have learned my lesson to read much more carefully next time. Thanks!
Secondary Fuel Filter Mistake - M25-XPB diesel
- Thread starter Monheganlover
- Start date
You ran it 30min, no point worrying now, I seriously doubt anything could be hurt.
Worry not.. You are not the first and for sure not the last to pre-fill diesel fuel in a fuel filter. Having run your engine 30 minutes with our incident suggests you have survived to try and mess up your engine in the future. 
Such things just happen, then we fix them.
Your decision to put “Clean” fuel in the filter is likely what saved your bacon.
What the YouTuber was trying to do for you was to eliminate the amount of air that gets into our fuel systems when we change the filters. While air is in the system fuel is denied the engine. No fuel no go.
You need to turn on a fuel pump and bleed the air out of the lines. Air can stop the high pressure pump from pushing fuel through to the injectors.
Do you know the bleed procedure on your engine? If not please consult the engine manual.
Not sure why you turn on the glow plugs. Only need for the glow plugs is to warm up the cylinder chamber prior to firing up the engine.
Good luck and happy sailing.
Such things just happen, then we fix them.
Your decision to put “Clean” fuel in the filter is likely what saved your bacon.
What the YouTuber was trying to do for you was to eliminate the amount of air that gets into our fuel systems when we change the filters. While air is in the system fuel is denied the engine. No fuel no go.
You need to turn on a fuel pump and bleed the air out of the lines. Air can stop the high pressure pump from pushing fuel through to the injectors.
Do you know the bleed procedure on your engine? If not please consult the engine manual.
Not sure why you turn on the glow plugs. Only need for the glow plugs is to warm up the cylinder chamber prior to firing up the engine.
Good luck and happy sailing.
Thanks. It's great to have your reassurance also! From now on, I'll carefully follow Nigel Calder's maintenance guidance. I may have mis-spoke about the glow plugs. I have a Universal M25-XPB which is self-bleeding. The manual states that - after changing out the filters - you should, intermittently, activate the pre-heat circuit by advancing the key. That primes and bleeds the system.
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That's a bit ingenuous. You need to learn the difference between what you need to do to turn on the fuel pump compared to what you need to do to turn on the glow plugs. This is two different actions. Running glow plugs longer than necessary is not good for the glow plugs.
Far as I can tell, on my engine, and per the operator's manual, the two actions, and the time frames for same, are similar. To start the engine above 41 degrees F, the manual recommends activating the preheat switch for no more than ten seconds by turning the key past the start position and holding it for 10 seconds or less then pushing the start button. On page 19 of my operator's manual, the manual states to bleed and prime the engine after a filter change simply "turn the panel key on and, intermittently, for 5-10 seconds, activate the pre-heat circuit." Presuming turning the key past start for 10 seconds or less is both for bleeding/priming and start-up, aren't they very similar operations? I've never held the key in the pre-heat position and, simultaneously, pushed the starter button. I've always started the engine by pre-heating with the key for that short interval and then hit the start the button. Am I missing something? Thanks!
Thanks to everyone for the wisdom. I still feel like an idiot but I guess God watches over fools sometimes
Yes, I do not fill the fuel filters. By holding the ignition key in the second position you are energizing the fuel pump which will fill the filters and any excess fuel will return to the fuel tank. Yes the glow plugs will also be energized. While the fuel pump is energized you will hear the clicking of the fuel pump when the engine is not running. Then release the ignition key to position one then press the start button. Holding the key on position 2 and pressing the start button is too much load for the battery.
You did well by reading the manual and following it's procedures. The self bleeding system of the M25-XPB is a true benefit. I have seen many well-meaning posters on this forum try to explain to C310 owners that they must bleed the system manually.
Slightly off topic, but good to know is that the proper idle rpm for your engine is, indeed, 1250 rpm. When I bought my boat, my surveyor convinced me that the idle rpm should be 950 rpm on any diesel. I went ahead and adjusted the idle from 1250 to 950, but the severe vibration that resulted ended up breaking the heat exchanger brackets. I found that the 1250 rpm setting results in a smooth idle, and does not injure the transmission during shifting, as many folks feared.
Good luck, and keep up the good work.
Thanks Tom! However, if I had read the manual a bit more closely, I would have known not to prefill the secondary filter with clean diesel 
A procedure I have used with success to avoid the dirty fuel issue after a filter change on my 310, m25 xpc engine is to fill the secondary or primary filter with Seafoam. It burns nicely, cleans the injector pump and the injectors as well. I use the whole can and have been doing this since I got my 310 about 6 years ago and used the same procedure on my former catalina 30 with the 2gm20 engine. Never had a problem or issue with starting either engine. It works for me although some say Seafoam really doesn't do anything. I suppose it really doesn't hurt anything. Just my procedure.
A contrary opinion. Install the filters empty. The consequence of dropping an empty filter are minimal, the consequence of dropping a full filter is a lot of diesel in the bilge needing to be cleaned. Which would you rather do, clean a pint or more of diesel from the bilge and under the engine or bleed the fuel system? Learning to quickly bleed the system is a good skill to have.
Dave's right. And with a self-bleeding M25XPB engine, why would anyone bother filling empty filters with fuel? I've sometimes filled my secondary with fuel injector cleaner. My M25 is not self bleeding, but a simple turn of a knurled knob on the engine with the fuel pump running takes less than a minute.
Most (all?) lift pumps have a small lever on them to manually prime the engine. Open the bleed screw and pump away, no damage to the starter motor or danger of filling the exhaust system with water. If the fuel level is higher than the bleed screw, once some fuel is brought to the screw, fuel will siphon from the tank and fill everything downstream.
Not long at all on my 3YM30 with a bleeding lever on the mechanical lift pump. Maybe a minute of pumping by hand and both filters are ready to go.