32 Sportfish Yanmar Fuel issues

[BruceK]

I have a 32 Sportfish with a Yanmar 315HP 6LYA-UTE. The boat has had fuel issues since I bought it 4 years ago. First of all the fuel gauges didn't work right from day 1. So I put in a Nema system and Martron transducer sensors with a Martron display. This was expensive but at least I can tell exactly how much fuel I have and approx GPH I am running. We had a Raycor 900 filter as a primary but the guy was running 2 micron filters in it. They were clogging up in no time and shutting down the engine. My starboard side would clog the engine after only a few hours running especially in rough water. I took the inspection plate off the top of the tank and pumped all the fuel and sludge off the bottom that I could get out. Still had problems. Talked to mechanic and he suggested changing to a dual Raycore 500 system with a vale that switches either filter or both. Then I had both tanks polished by USA Fuel systems out of Warwick RI. I am now up to about 4K trying to fix this ongoing problem. Last Friday the engine seamed to be a little sluggish like the filter was clogging again only after about 10 hours of running and again this happened in fairly rough seas (3 footers or so). I switched to my other filter started up with no issues and headed back to the dock. Yesterday I changed the filter which was a 10 Micron 2010-TM and it was very dark in the bottom and not bad about 1/4 of the top. The fuel was not all the way to the top when I took the cover off the Raycore unit and seams like it was only using 1/2 of the filter. I did take a 30 micron filter out but figured running a 10 would be better. Now I am wondering if I should go back to the 30 again because the 10 may be restricting fuel flow but I don't want to rely on the secondary filter to catch all the crap that gets past the Raycor 30 micron instead of a 10. The Mechanic assured me that the Raycore 500 has plenty of fuel flow capacity for the Yanmar. Now I am wondering how many hours should I get out of a fuel filter and should I go back to the 30 Micron.

[jleonard]

Put the Racor 900 as the first filter and run 30 micron elements. Use the Racor 500 next with 10 micron.
Multi stage filtration is the way to go.

[RobS]

I think he pulled the 900?

[BruceK]

Yes they pulled the 900 and replaced it with the 500. I have double filtering as the Yanmar has a filter mounted to the motor.

[jleonard]

Oh I assumed Everybody kept their old parts.

[RobS]

The 900 should have been left as the "mud filter" being the first line of defense and the 500 installed between that and the engine ... the 500 is marginal as to flow rate for the 6LP and once put into a tasking situation like this it will not do well.

[BruceK]

RobS
Do you know if the 30 micron and the 10 micron have different flow rates?

[RobS]

Flow rates of the filters? Do you mean restriction? The restriction only increases as the filters get dirtier/plugged...

[jleonard]

I think in theory they would be the same at least until they started to fill with contaminates.
According to the Racor site's formula for estimating your engine's fuel flow (gph=hp x .18) you need 57 gph capacity.
The Racor 500 is 60 gph.
So with a new element it is barely adequate. ( those calculations agree with Rob).
According to another site I just looked at quickly your engine should have a 10 micron filter at the engine.
If all the above is true your best bet right now is to use 30 micron filters in your Racor 500.
But adding a 30 micron with large capacity ( like a Racor 900) upstream of
everything would be primo.
Then you could go to 10 in the dual 500.

Edit. I went to this same system in my boat 11 years ago to address a filter clogging situation. Haven't had an issue since (knock on wood). I am only flowing about 2 gph but now I never see any restriction on my vacuum gages