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Morning, folks. I've got twin '02 DF140s with about 500 hours, saltwater but properly flushed and maintained. Had her out and after about 15 minutes cruising I got an overheat alarm on both engines, so I shut them down and floated around till they cooled off. Restarted and the starboard engine alarm resumed within seconds, but the port engine ran fine. Shut down starboard and got her home on one engine. Checked thermostats first, port engine is fine but starboard has oil in the water, the dreaded chocolate milkshake. When I removed the oil filler cap to drain the oil, I got a little bit of oily water draining from the water intake grates on the lower unit. Checked cylinders with a bore scope and it doesn't look like there's any water in them, and compression is between 185 and 192 on all four. No visible leaks, excess salt deposits, or oil on the block or around head gasket, no oil pooling in the case . I'm going to pull the oil cooler first, but if that's not it where should I look next?
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More info, I think I'm screwed here. Got the oil cooler off and hooked the hose up to the side flush port. Water is coming through the oil filter, so water is getting in somewhere internally.
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Don't be too quick to scrap those engines. The problem may well be the oil cooler. I have a pair of DF140s with 2,150 hrs on them.
Last summer, I had found a trace of seawater in the port engine oil and had noticed an oil sheen in the exhaust water of the starboard engine. After bypassing the coolers (with same results as you) I was certain that both items indicated corrosion of the block or head alloy. I felt that way because the engines are 14 years old and my experience over the years has shown me that outboard alloy deteriorates in the salt water in 12 to 13 years. I have had three engines that have failed in that time.
Last fall while shopping for new engines, I happen to see a post on the Classic Mako forum concerning a pair of used DF140s that a guy was interested in. Turns out that he did not buy them, but he mentioned concern about corrosion in the "typical bad spot". Goggle searches led me to understand that other DF140 owners have had problems with water in the oil as well as oil in the exhaust water because of failing O-ring seal(s) in the oil cooler.
That caused me to remove my oil coolers. Sure enough, they both showed signs of failure. In both coolers there was a deposit of salt residue in part of the cooler that corroded the alloy adjacent to the O-ring seal(s). Removed the residue, cleaned up the corrosion, built up the corroded alloy with Metalset and installed new O-rings. Ran both engines on earmuffs for a half hour with this temporary fix, no water in oil, no oil in exhaust water. The repair was done last December, so I was not able to test them with a hard run in the water. Last week I ran 4,200 RPMs for an hour to an offshore spot, trolled all day, and ran 4,200 RPMs for an hour home. No water in the oil and the fluid levels were fine.
I had planned to order new oil coolers, but before I did I wanted to be certain the problem is fixed...and I believe it is.
Last edited by Ole Joe; 07-24-2018, 08:27 AM.Comment
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Pretty common problem, most people don't do the required routine service on the oil cooler, including dealers.Comment
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I do not recall mention of routine service for the oil coolers being published in the owners manual, service manual, or parts manual...kinda disappointing because it is such a simple fix.
Actually, I spoke with several authorized dealers about finding water in the oil and none mentioned the coolers or o-rings as possible causes. It was only because of the comments on this forum and Classic Mako that I was able to zero in on the O-rings.
That said, these are the best little engines I have owned. And, I understand the new ones are even better.
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