Ask Professor Diesel

Caring for engines after a not-too-long hiatus.

I left my marina with my seacocks closed…

Should we do end-of-season oil changes or can we stretch the old oil into the next season?

I plan on being away from my boat for two to three months and during that time, I plan on having someone periodically run my diesels dockside…

 
Question: I have a 1989 38-foot Bayliner with twin 175-hp Hino diesels that have been retrofitted with turbochargers, thus raising each engine to 210 horsepower. As I go from cruise to wide-open throttle (approximately 23 mph at 2800 rpm), turbo exhaust temperatures increase from 700F to 950F on the port engine and 850F on the starboard. When

 
Question: The boys at the Ko Olina harbor are having a heated discussion concerning motor oil. Since Costco hit town, we’ve all been able to buy Chevron 15W-40 Delo 400 heavy-duty motor oil at ridiculously low prices. But what about the older engines we’ve been using straight 40W Delo 400 and other single-viscosity products in for years? Can we

 
Question: I own a 1996 43-foot Hatteras with twin six-cylinder Detroit Diesel engines. I change the oil approximately every 100 hours of operation. At this point, I have 1,200 hours on each diesel and so far have only used non-synthetic oil. Is a synthetic or a blend of synthetic and regular oil contraindicated for this aged engine for any

 
Question: I have a 29 Phoenix with twin, 1984-vintage, 170-hp Yanmar diesels with 1,000 hours on them. While the boat seems to run fine, I have one issue. During operation, the temperature of each engine rises normally at first but then keeps on going, not to the point of setting off alarms, but close. Pegging the engines (i.e., throttling them

Question: My mechanic friends tell me not to let my diesel engine idle for long. They say that it should either be under load or turned off. I hear a lot of diesel engines in trucks idling at truck stops for hours though. Is there a difference in the two types of diesel engines or are my mechanic friends mistaken

Question: I have a 1990 Carver Yacht with two 375-hp Caterpillar 3208 diesels. The starboard engine works fine, but at 2000 rpm the port engine overheats. Once the temperature hits 200F, I slow down to prevent damage and everything returns to normal.