Engine bogs down under load

[WindyT]

Hi folks,
A bit of a puzzler for me. Im currently offshore near marathon and planning to change my fuel filters for the third time in a month tomorrow. Until now I've never had any issue with the engine. We are cruising along at 2300 rpm without issue but if I head towards win and out the bow through some larger waves (as when I was in the Gulf Stream two hours ago), the engine will bog down and die unless I take some of the load off by either rolling out the jib or turning back downwind. 
My concern is sediment getting shook up in worse conditions and there was some in my racor when I changed it a week ago after same symptoms.
I'm running a Racor R20S and a Fram P7514. I'm considering changing the Racor to a R20T as a temporizing measure until I get the tank flushed and cleaned.
No water in the fuel. No other changes. Anything else I am missing here?  Thanks for the last minute help!

[scgunner]

Annie,

Sounds like you've got gunk in the tank which is loading up your filters and starving the motor. You can pull the sending unit and take a look in the tank(you may need a flashlight and mirror), if you can't see the bottom you've got a problem. Draining, polishing, cleaning to follow. Some things you can do to avoid future reoccurrences, treat fuel with biocide and water-sorb and keep your tank as full as possible, especially when the boat is going to sit for extended periods.

[Ron Hill]

WindyT : What engine?
I hope that you've checked to make sure that the screen on the fuel pickup tube has been removed!?! 

A thought

[Roland Gendreau]

I misdiagnosed a failing lift pump as a fuel filter issue.    It would pump sufficiently to start and run at lower rpm , but when the throttle was further opened, the engine would lose power and stall, similar to a fuel filter getting clogged.  It was only when I disconnected the fuel line coming from the pump and tried to pump fuel  into a jerry can that I determined the pump wasn't pumping.
Some will say that fuel will siphon from a full tank to the engine without a lift pump, but that isn't true if the pump itself is blocking  the flow.

I also think the 2 micron racor is inappropriate as the downstream filter is 10 micron.

[Stu Jackson]

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I also think the 2 micron racor is inappropriate as the downstream filter is 10 micron.

There is a philosophical issue here:

1.  Filter experts always say "Coarse to fine"

2.  C34 skippers sometimes say: "I'd rather put a finer filter where I can bloody well reach it, i.e., the Racor under the head sink."

BTW, the secondary filter on the engine is not 10 micron.  I think Maine Sail finally pointed out that they were between 25 & 30 micron in a fuel filter post many years ago.

[Ron Hill]

Guys : There are C34 owners with the M25XP engine that have removed the "course" engine mounted fuel filter from the engine and remounted it before the 'fine" Racor filter!!

Once again- I ran my engine on gravity feed alone for over a year (at least 500hrs!!).  I connected the fuel pump to the blower switch and could check if the engine RPM increased when the fuel pump was ON (Rational - I used that setup to check for a clogging/clogged Racor filter)

A thought

[Paulus]

WindyT
You might also check the air vent to the fuel tank.  It might be partially blocked.
Paul

[Roland Gendreau]

>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>

I also think the 2 micron racor is inappropriate as the downstream filter is 10 micron.

There is a philosophical issue here:

1.  Filter experts always say "Coarse to fine"

2.  C34 skippers sometimes say: "I'd rather put a finer filter where I can bloody well reach it, i.e., the Racor under the head sink."

BTW, the secondary filter on the engine is not 10 micron.  I think Maine Sail finally pointed out that they were between 25 & 30 micron in a fuel filter post many years ago.

A good resource to understand filter specs is here:  https://www.fleetfilter.com/filter/Article--Micron-Ratings-in-Filters.html   

Nominal filter micron spec's do not tell the complete story. 
2 microns is the size of bacteria.   Seems like filtration overkill to me.


   

[Ron Hill]

Roland : Then do as I mentioned. 
Remove your engine filter from the engine and put it before the Racor filter!!

A thought