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.