Inconclusive autopsy

After disassembling and inspecting  Ms. Bettencourt's entire raw water cooling system, I have been unable to find any clear-cut cause for the old diesel's intermittent temperature spikes. I have removed, cleaned and reassembled the heat exchanger and removed the raw water pump and replaced its impeller. I have checked all the passages in the pump. All of the hoses are being removed and replaced.

I didn't think the heat exchanger looked too bad, but there was some sand in it and a scrap of broken impeller from some previous melt-down. A long soak in vinegar may have removed some occult scale and might improve performance.

The photo at right shows the pump with the (black) impeller I removed and replaced. The take-out impeller looks a little ragged, but, again, unlikely to be dysfunctional. I put the new blue impeller in the photo for comparison purposes.

 Here's a closer look at the old and new impellers.

The take-out impeller had been in use about 200 engine hours. The comparison impeller is a different brand, but otherwise compatible with the Oberdorfer pump. You may click a photo to enlarge if you would like a closer look.


The result of all this work will be a cleaned out a raw water cooling system with all the soft components and clamps replaced, and a neatened-up engine box. If the overheating problem persists, I can at least be confident that the cause is not in the raw water cooling system.

I am putting it all back together now. There will be a test run sometime soon.

Problem search expands

Please recall that on her last voyage Ms. Bettencourt's old diesel began to exhibit some troubling temperature rises. After checking the usual suspects, it seemed to me that the problem was either a disintegrating cooling water pump impeller or a clogged heat exchanger.

I removed the end cover from the pump (if you click to enlarge this photo, it's that doohicky left center that says "Oberdorfer" on it).

Anyway, the impeller looked OK, so I moved on to remove the heat exchanger. This revealed that front end of this engine really needs a cleanup, so here's an obvious project expansion.

With the heat exchanger on the bench with its end caps off, I looked down the barrel expecting to find at least some clogged passages.

Actually, it didn't look too bad. A length of wire moved through the small passages easily. There was some sand,  and, surprise, a piece of water pump impeller. This clue will lead me to look under the Oberdorfer cover yet again, this time more carefully.


I have ordered new end caps and gaskets for the heat exchanger and they won't be here until Wednesday, so there's time for a more thorough heat exchanger cleaning;.

The heat exchanger goes into a tank of vinegar for a long soak. Helpful hint: old plastic tool boxes are often big enough to accommodate strange shaped parts for soaking.





Meanwhile, it's time to check the sacrificial anode. The take-out part does not measure up.

The zinc on the left has obviously been doing its job and will be replaced by the spare on the right.

Those discs at the top of the photo are the end cap gaskets, which will also be replaced.

The black rubber sliver in the foreground is the impeller piece found in the cooling water intake end of the heat exchanger.




After two days in the vinegar bath, the heat exchanger comes out looking relatively shiny.

The vinegar turned black during the soak and I found a lot of grit and small black flakes in the fluid.

I blasted both the large and small passages out with the garden hose and got only clean water out the ends. Perhaps all this will improve the heat exchanger's performance. But, I doubt that the amount of stuff I cleaned out of this heat exchanger will explain the 4-5F engine temperature creep that started this whole project.

Incidentally, a further explanation of the anatomy of this device might be in order. Here's how it works: The engine coolant (antifreeze) goes into one of the  big elbows shown in this picture, through a large central tube, then back to the engine via the other elbow.

Cooling water, supplied by the Oberdorfer pump, goes in and out of the small inlets at the bottom of this photo. The water circulates through many smaller tubes around the central tube, then goes out through a hose that connects to the exhaust elbow at the other end of the engine. In this photo, the sacrificial anode screws into the fitting at the top right of the cylinder.

Anyway, the story isn't over yet, because I am not convinced the cause of the problem has been found. While I am awaiting parts, I'll give the raw water pump impeller a closer look, and probably replace it. And since I have the whole thing apart, I'll replace all the hoses and hose clamps and de-grease and clean the front of the engine.

At this point, I can't imagine how this project could snowball any larger, but that doesn't mean it won't. Please check back later for a report on results.

Taking subtle hints seriously

Ms. Bettencourt is back at her home dock after an uneventful highway trip back from the St. Johns River and Tropical Storm Andrea.

Unpacking was delayed by continuing rain and intervening duties. Today was devoted to sorting through the post-cruise detritus, re-stowing, refueling and a general cleanup.

Ms. Bettencourt's exterior is starting to look a bit dowdy. She needs to have her cabintop rails removed and refinished and to be stripped and repainted from the rubrail to the hardtop eaves.

She has a reservation for a slot under the shed at the Augusta Ports Authority at the end of the month.

Meanwhile, I am pondering a couple of powerplant developments that surfaced during the Florida trip: The engine was running a few degrees hotter than comfortable, and the transom was blacker than usual with soot at the end of the trip. I am more worried about the former than the latter.

I think the soot on the transom was the result of a hard four-hour run at nearly 80% power. We pushed the engine for an extra 1000 rpm, trying (successfully) to get to a marina before closing time.The carbon scrubbed off fairly easily. I included some Cetane Boost additive with the red off-road diesel at fill up. We will be less heavy-handed on the throttle in the future.

The temperature creep, on the other hand, is a serious matter. Ms. Bettencourt's engine, a marinized three-cylinder Kubota tractor motor, is one of about only 1100 of its kind built between 1977 and 1983. The engine is known to be "bulletproof"  if well-maintained. Up until now, she has held her operating temperature steady at 180F. At times on our most recent cruise, however, the needle has moved alarmingly close to185.

Even small changes in such an old machine are to be disregarded at the operator's peril. So, after checking to assure a free flowing cooling water intake and a full antifreeze reservoir, I am beginning to think there may be a problem with the heat exchanger. (It's that brass cylinder shown at the bottom of this photo).



A boat engine heat exchanger functions as a radiator does for a car motor. In a car, air flowing over engine coolant circulated through the radiator removes heat and keeps the engine running within specifications. On Ms. Bettencourt, the cooling medium is raw water from the river, lake or ocean upon which the boat is floating. Engine antifreeze is circulated through a circuit inside the heat exchanger. Raw water pumped into the heat exchanger and around the coolant circuit removes heat from the engine antifreeze.

Tomorrow, I'll check the raw water pump impeller and pressure test the coolant expansion tank cap. If these components are within specs, the next step will be removal of the heat exchanger for inspection and, if necessary, repair.

It would not be surprising, in an installation this old, to find calcified or otherwise obstructed raw water passages in the heat exchanger. If this turns out to the the case, the fix should be fairly easy.

Please check back for an update in a future post.

Listening to the weather gods

This morning’s highlights: Tornado Watch. Flood Warning. Local rainfall up to 5 inches. Three inches of rainwater already accumulated in the dinghy. Tropical Storm about 200 miles southwest, moving northeast.

And here we are in Florida, at Hontoon Island State Park, thinking about continuing south on the St. Johns River to Sanford. “What do you think we will do when we get to Sanford?” I ask my cruising buddy Paul.

“Probably sit in the boat in the rain and think about calling for delivery pizza,” he replies without hesitation.

“The weather gods are trying to tell us something. We may never get to Sanford.”

In my role as Captain, I reason that since the weather gods have already sent us Andrea, the first named storm of the Atlantic hurricane season, perhaps we should take heed. Have a look:

Uniform of  the day ... day after day after day

Looking for sunshine... without success

Pitching and rolling on Lake George

Waterproof osprey chicks 

As this is being written, Ms. Bettencourt is retreating northward.

We have seen some nice wildlife – bald eagles, many ospreys with young, wading birds, a congregation of wood storks, and countless alligators. 

And, since even a stormy time on the water is better than pushing the lawnmower, this trip is still a success.

We expect to be back at Acosta Creek Harbor before dark, and on the road to Augusta tomorrow.

Provisioning the lifeboat

All the stars are beginning to align for the St. Johns River cruise. Ms. Bettencourt got a good external scrub down yesterday. Her fully-serviced trailer is parked out front. The plan is for my friend Paul and I to haul the boat Monday, then park the rig at the Augusta Ports Authority for loading and departure early Tuesday.

I will be doing the grocery shopping Monday afternoon, and it appears I won't need to buy much. Paul's wife Erena is sending along 24 sausage and egg muffins "which may be eaten hot or cold," plus a quantity of her famous chocolate chip cookies. Dia is providing a shrimp salad entree for a main meal, plus nutritional advice such as "don't blow your diet."

Our carefully-planned cruise itinerary has us in marinas with restaurants nearby every night of the trip.

So, the shopping list is sparse: Sandwich stuff for lunches, soft drinks, fruit and ice.

Of course, prudence demands that we also get some bratwurst, buns, chips and double-stuff Oreo cookies to provide sustenance should disaster strike.

Who knows what could happen?  We might have to abandon ship. Preparedness is good.