Caterpillar 3116s Overheating - No More!

  It's only been about two years, but we've finally gotten some real success in our search to find out why the engines on Swing Set have been overheating. One may wonder, admittedly so, why it would take so long to figure out a seemingly simple problem. Without repeating all of what I've been writing about since we discovered the problem while we were in The Bahamas way back in 2012, I'll try to explain.

  I needn't say here that I'm no mechanic. Just reading this blog will be testament enough to that particular fact, but I try. A friend recently said, after I had been recounting some success at a minor repair, that he "pays people to do those type of things". I replied that given our economic station in life, it's necessary that we do at least some of the maintenance on our boat, because if we didn't, there are two certainties; either us or the boat would remain broke.

  So...the story:

We know that Swing Set was capable of running at cruising speed (2500 RPM) for hours at a time, at least until we had to run from Highbourne Cay in The Exumas over to Nassau when our steering went out. I did replace an impeller on the port engine when we were in Spanish Wells because the port engine was running hot. It wasn't until we were leaving Rum Cay in the far Bahamas that I discovered an overheating problem on our starboard engine. I replaced the impeller in the raw water pump on the starboard engine, but from that point on, both engines ran marginally hot, and remained that way until we got back to Miami. Then began my lengthy trial and error attempt at cleaning in place the raw water systems on both engines.

  This process took a great deal of time. First is doing the process itself. Then, typically we would have to wait for a weather window to sea trial in order to see our results. We did get some improvement of the time duration it would take for the temperatures to creep up. Sometimes this would happen faster on one engine than the other. When that would happen, then another process of determining a root cause would begin by pulling sea strainers, checking for proper water flow from the exhaust. (The exhaust actually exits below the water line, but the spent cooling water leaves the boat right at our water line, making an actual determination of just how much water is flowing a difficult one.)

  Over the last several months, I improved my method of cleaning the heat exchangers, learning something new at each attempt. I did lots of reading on social networks, which will leave a person thinking everything is broken, or the engines are worth nothing but scrap. But you have to get ideas from somewhere.

  I installed new thermostats. I changed out temperature transmitters to see if the issue would migrate from one engine to another. (This is when one engine would be running considerably higher than the other.) During this time, there were times when we went out for a sea trial only to find we couldn't get on plane, so that problem would have to be resolved before resuming our search for the overheating issue.

  Every time I would have a conversation with a fellow boater who had similar experiences in the past, or a well meaning blog reader would pass along some advice, I'd try something new. I pulled exhaust elbows, tightened fresh water belts, and inquired about our "after coolers" with our Caterpillar mechanics, all with no results, but learning new things each time about how to avoid scraping all the skin off of my knuckles when doing mechanical work.

  I began to suspect our coolant. We had been using an extended life coolant, installed at least five years ago when we were in St. Louis. The Caterpillar books stress the need to use fresh coolant, along with the proper additives, or else all kind of horrible things would happen to our engines, overheating was one of those things, along with the threat of our descendants for many years being subject to all kinds of calamity.

  But the Caterpillar reps down here dismissed the "old coolant" theory. So, I recently replaced both radiator caps, and the raw water pumps entirely on both engines. (The raw water pumps were pumping water, each with newer impellers, but both pumps were leaking water at the seals, a warning sign of impending doom regarding the seals on the oil side.)

But here is what kept nagging at me; a mechanical issue regarding both engines at the same time would be coincidental at best. I could understand both engines needing the heat exchangers cleaned as they would accumulate scale at the same rate, but since both engines were now overheating at the same rate, I suspected a common denominator, and the stale coolant was common to both engines.

  Last week I drained the coolant from both engines, getting most of the seven gallons from each engine without spilling any into the bilges. This alone is an accomplishment, folks. I replaced the coolant with fresh water temporarily. We had to wait again for a weather window, and yesterday was the day.

  We ran straight out towards the Sombrero light, just about at the three mile limit, and then kept going. Within just a few minutes, I knew I was on the right course. Both engines reached no more than 190-195 degrees and stayed there for 45 minutes, running at 2500 RPM. Sweet!

  This morning I flushed the raw water systems on both engines, checked the oil, and sent our Caterpillar a note detailing the success of our sea trial. We're keeping our service appointment. I want to pressure test our coolant systems, do an oil analysis, and just have a qualified mechanic on board to give us a preventative "check up" in the engine room. After pressure testing the cooling systems, we'll install Caterpillar Coolant at the recommended coolant/water ratio.
UPDATE: For anyone foolish enough to follow any mechanical advice I may give, I wanted to add some thoughts to this post after talking to a different CAT mechanic and some boat neighbors who seem to know what they are doing.
  No one except the CAT manual agrees with the older coolant being the issue with overheating. However, I do think additives and coolant viability (or newness) can play a part in how the coolant reacts to the metal in your engine. Straight water, over time, can pit the insides of an engine and cause mucho, mucho problemos. So putting new coolant in was a prudent thing to do.
  I wish I would have installed the new raw water pumps and ran the boat before draining the coolant...because the old pumps were leaking at the weep holes due to the seals going bad. Now...I've known before...but somehow forgot, that if water is leaking out, then air can be leaking in, and air leaking into the raw water pump can cause cavitation which disrupts the water flow, hence reducing the efficiency of the cooling system.
  There's more. Even though I am very happy with our engines running at 195 degrees, I'm being told that if we have 180 thermostats installed (which we do) then the engines should run at 180 degrees at all speeds, not just our leisurely 9 M.P.H. when not on plane.
  For now we're standing pat. From the factory the 3116s come with a 195 degree thermostat, so I don't think running at the temperature at cruise is going to hurt a thing. But I'll be paying close attention to any future temperature increases.

Another update: When we try to run both engines off of one fuel tank, it appears that the supply is not adequate to run both engines and one or both are starved for fuel at higher rpms. This is also causing the engines to overheat.

  Last night might have been one of the first in a long time that I didn't spend at least a few minutes, or hours, laying awake wondering why we were having overheating issues.

  But it hasn't been all about engine problems. My "systematic" painting of the aluminum trim in the cockpit has still been ongoing, and I made another dinghy seat improvement. Check out the picture above.

  Our dinghy seat is on the fourth generation. You might recall how the original seat began to de-laminate and fall apart while we were in The Bahamas. I repaired, then replaced the seat when we got back to the U.S., using plastic fence board. I've used plastic fence board for some structural items in the engine room, but the dinghy seat needs to flex some, so the stiff plastic fence board broke as we were pounding over some waves last year. I again replaced that seat with one made of wood, priming and painting it to protect it from the elements. I thought that that seat would last as long as the dinghy would.

  While we were in Key West a few weeks ago, I noticed that the wood was rotting under the paint! I decided right then that I'd bite the bullet and spend the money on Starboard and do the job right. A few days ago we took the scooter to Home Depot and bought a 2' x 4' sheet of Starboard, had the nice folks there custom cut it for us, and then we rode home on the scooter with the seat tucked under Rosie's arm, along with some aluminum angle we bought to add as bracing. An alternative would have been for Rosie to bring a cab home to the marina with our purchases, but what's the fun in that?

  Rosie and Holly are posing in the dinghy when it still had the "old" seat. The sun is getting hot down here now, and the small umbrella we have been using to provide some shade for our little buddy has been getting blown around on some windy days, and the big umbrella that we had also used occasionally does not have the support needed at the base and has cracked the fiberglass surrounding the mount on the dinghy. I ordered a bimini top for the dinghy, so I made the new seat so the top could attach to it, meaning it had to be wider.

  Making it wider seems like a no brainer, right? Well, the seat can only be so wide so it fits into the straps on the dinghy made to hold it in place, and you don't want the seat to rub anywhere on the single layer of the tubes, so I made the seat "float" over the tubes, wide enough so that I can mount the bimini rails on the outside edges of the seat. I needed a width of 48" and the dinghy seat mounts are 40" apart. I'll post some pictures of the new top once I get it installed next week.

  Basking in the success of our sea trial, and without any other immediate problems hanging over our heads, we're going to enjoy our Memorial Day weekend starting this afternoon when we take the dinghy out on what is predicted to be one of the last calm weather days for a while. We'll take at least a few minutes to remember why we have this holiday. Hope you do too.