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Author Topic: Engine bogs down under load  (Read 338 times)

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WindyT

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Engine bogs down under load
« on: February 16, 2020, 07:40:26 PM »

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 Iíve 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.
Iím running a Racor R20S and a Fram P7514. Iím 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!
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Annie C  1990 C34  Hull #1041   Charleston, SC

scgunner

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Re: Engine bogs down under load
« Reply #1 on: February 17, 2020, 07:45:35 AM »

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.
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Kevin Quistberg                                                 Top Gun 1987 Mk 1 Hull #273

Ron Hill

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Re: Engine bogs down under load
« Reply #2 on: February 17, 2020, 02:01:01 PM »

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

A thought
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Ron, Apache #788

Roland Gendreau

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Re: Engine bogs down under load
« Reply #3 on: February 17, 2020, 06:35:35 PM »

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.




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Roland Gendreau
1992 MK 1.5
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Bristol, RI

Stu Jackson

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Re: Engine bogs down under load
« Reply #4 on: February 18, 2020, 08:18:23 AM »

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

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.

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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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Ron Hill

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Re: Engine bogs down under load
« Reply #5 on: February 18, 2020, 04:15:16 PM »

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
« Last Edit: February 18, 2020, 04:22:56 PM by Ron Hill »
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Ron, Apache #788

Paulus

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Re: Engine bogs down under load
« Reply #6 on: February 19, 2020, 06:19:01 AM »

WindyT
You might also check the air vent to the fuel tank.  It might be partially blocked.
Paul
« Last Edit: February 19, 2020, 06:53:59 AM by Paulus »
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Cool Change 1989 #944

Roland Gendreau

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Re: Engine bogs down under load
« Reply #7 on: February 19, 2020, 06:56:21 PM »

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

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.


   

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Roland Gendreau
1992 MK 1.5
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Bristol, RI

Ron Hill

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Re: Engine bogs down under load
« Reply #8 on: February 20, 2020, 04:21:13 PM »

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

A thought
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Ron, Apache #788
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