Temporary Drops in RPMs

[Jim Keller]

Gordon,On the way back from our summer cruise to the North Channel on ORION, the RPMs would sometimes drop down anywhere from 100 to 2000 below the 3000 that we were running. I suspect fuel or fuel filter problems. I did change the Yanmar fuel filter on the engine, but it still did it. I did not have a spare filter for the Racor 110A so did not change that yet. Any thoughts on what to check?Jim KellerORION

 

[Guest]

Your Racor Filter is Clogged

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[Paul]

Fuel pick up tube

I had a similar problem which turned out to be a blocked screen in the fuel pickup tube in the tank. Took the tube out, (couldn't even see light through it) cleaned it (probably should have had the tank cleaned, but didn't have time) swapped all the filters and everything was good to go!

 

[Gordon Torresen]

RPM drops

Jim: You could be experiencing the affect of air passing through the system. Your 4JH2 is considered self-bleeding. Air in the lines will usually be unnoticed unless the volume is great enough. Then you will experience anything from very slight RPM changes to total stoppage. Air can get into the system while motoring in a seaway when the tank is less than full. Partial blockage of the pick-up tube or primary filter can exascerbate a small air leak at any fitting because it tends to increase the vacuum in the line. Take a look at your primary filter. It will usually give an indication of what is going on in the tank. If you see water or bits of algy, it's time for tank work. You probably have a strainer on the bottom of the pick-up tube. Whenever we have cause to work in a tank, we remove the strainer, hoping that any debris will get to the filter where it is much easier to dispose of.