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Old 10-22-2019, 10:24 AM   #18
Rufus
Senior Member
 
City: Great Lakes
Country: USA
Vessel Model: OA 440
Join Date: Aug 2017
Posts: 418
Antares,

Good advice. But I'd add that a serious overheat would likely just result in a blown head gasket....an inconvenience for sure, but certainly not catastrophic. I find it interesting that the forum has a standing "sticky" for changing the head gasket on the Lehman, the beloved engine of the trawler community. What a joke. Try running a 120(or turbo'd) Lehman or Perkins (even a Cummins) for extended time near the maximum rating and see how long they last....BOOM!

Our boat has a sensor that trips an obnoxious audio alarm when the coolant temperature reaches 195 degrees F. It's happened to me once when a misaligned raw water pump pully caused the drive belt to jump off when I pushed the power lever up. The alarm gave me plenty of time to snatch the power lever back before the temperature even reached boil over. I've thought about adding those clamp-on temp sensors on the exhaust hoses, but it seems it would be redundant as the existing sensor would probably trip first. Anyway, there's no way I'd contemplate an engine change for a blown head gasket. Keep an eye on the cooling system, including the raw water pumps and be sure the warning system functions, and I'm convinced they'll outlive their contemporaries by a large margin. The fat torque curve on these big displacement gems tells a story. The 220/250 engines are not stressed.

I typically operate the engines at 15-1600 rpm (hull speed plus a knot or so), but always run the engines up to 2500 (14-15 knots) for about 10 minutes each hours. Max is 2800. They never, ever show signs of overheating. Temperatures stay rock solid at 170. That said, I've removed and rodded the engine and transmission oil coolers to insure that the cooling systems is functioning at max efficiency....and that's something I'd make a periodic maintenance task....especially in salt water. I suppose if the engines were run at maximum rpm all the time, there would eventually be issues (as there were with the 300/350s in sport boats). But so too would there be problems with other brands in this power range. These engines give me super efficient slow cruise, and the option of (semi) planning at 14-15 when I need it on occasion. (The boat will reach 17 knots at 2800 rpm).

Treat them with respect, and they keep on keepin' on. The urban legend is nonsense.
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