RPM Issue Solved

Dec 16, 2011
257
Catalina 310 Atlantic Highlands
I am sure folks with more diesel experience than I have will know the answer right away, but I wanted to share an experience I had and what the solution turned out to be. In traveling across the bay to anchor for a day of swimming, I noticed that the RPMs were dropping off intermittently. I was cruising at around 1800 RPMs, and suddenly they would drop off to 1500 (or lower) and then pop back up to 1800. It happened a couple of times on the way to anchoring (and in retrospect I should have just turned around) but I had guests on the boat who wanted to go for a swim so we anchored. I also just assumed the throttle cable was slipping (had that happen in my older boat) and that I could tighten it up when we got back. Later, while taking up the anchor to return hom, the RPMs began swinging wildly down and back up and then she stalled. I couldn't get her re-started and had to be towed back to my mooring. After replacing the primary and secondary fuel filters, she seemed ok for a day but then starting having the problem again. It turned out that this connector (the one on the red wire, see pictures) hadn't been plugged in correctly a couple of years ago when the previous owner (or his marina) changed the fuel pump. The male connector hadn't inserted properly and was just resting against the female connector. Apparently, the vibrations had finally caused the plug to start intermittently making contact, so the fuel pump was intermittently stopping. Once my mechanic re-seated the connector, no more problems. Just thought it might be useful to share this experience (and maybe save someone the cost of a mechanic).
 

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Mar 22, 2009
360
Catalina 310 Gulfport Small Craft Harbor, MS
I had very nearly the same exact problem back in July. But mine hit while trying to motor back into the harbor right as a T-Storm was hitting with 35 knot winds. If I throttled up the motor would choke down to 1500ish RPM. But if I kept the throttle back I could maintain 1500. Wind was blowing me towards the rock jetty so I was pretty nervous. Had USCG vessel coming in behind me so I was considering calling him to push up against my leeward side to keep me from drifting into the rocks. Then once past the jetty I thought I would just let the wind blow me over to the fuel pier for a controlled crash...but I made it past the jetty and the fuel pier and winds slacked off to about 20 so I was able to milk the engine back to my slip.

Bracket holding the starter solenoid (I think that is what it was) broke and the unit was shaking/vibrating pretty good. Somehow this was tied into the fuel pump and it was intermittently stopping.

Cheers,
Jim
 

pk104

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Jun 30, 2009
207
Catalina 310 Atwood Lake
Amazing how such a simple thing can cause such a big problem. Do it right the first time and double check your work is a recurring lesson for all of us.
 
Aug 23, 2014
164
Catalina 310 Guntersville, Alabama
I am sure folks with more diesel experience than I have will know the answer right away, but I wanted to share an experience I had and what the solution turned out to be. In traveling across the bay to anchor for a day of swimming, I noticed that the RPMs were dropping off intermittently. I was cruising at around 1800 RPMs, and suddenly they would drop off to 1500 (or lower) and then pop back up to 1800. It happened a couple of times on the way to anchoring (and in retrospect I should have just turned around) but I had guests on the boat who wanted to go for a swim so we anchored. I also just assumed the throttle cable was slipping (had that happen in my older boat) and that I could tighten it up when we got back. Later, while taking up the anchor to return hom, the RPMs began swinging wildly down and back up and then she stalled. I couldn't get her re-started and had to be towed back to my mooring. After replacing the primary and secondary fuel filters, she seemed ok for a day but then starting having the problem again. It turned out that this connector (the one on the red wire, see pictures) hadn't been plugged in correctly a couple of years ago when the previous owner (or his marina) changed the fuel pump. The male connector hadn't inserted properly and was just resting against the female connector. Apparently, the vibrations had finally caused the plug to start intermittently making contact, so the fuel pump was intermittently stopping. Once my mechanic re-seated the connector, no more problems. Just thought it might be useful to share this experience (and maybe save someone the cost of a mechanic).
hmmm... this sounds like the problem i just had. Thanks for the pictures. Maybe it is a connection instead of fuel filter. We put a new fuel filter in before our trip. Thanks again.
Neal