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Dark Oil in BF250D

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doc_stressor

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I just had my marina do the first 100 hr service on my BF250D. They told me that the oil was very black. Dark enough for them to take note of it. I did the 20 hr service myself and the oil was clear. Barely able to read the level on the dipstick. So something must have happened over the next 80 hr. I'm sorry to admit that I had not been checking the oil over that time.

I'm fairly knowledgeable about lubrication technology and I know that the most likely causes of dark oil are overheating and oxidation from fuel dilution. But I never got an overheat warning and the oil level remained constant over the period. They did not do a computer dump to check for overheat codes. The engine runs at 190 degrees on the Honda gauge, which seems high for an outboard to me. Is this a normal operating temperature for this engine? Does anyone have any ideas about what else could have caused excessive oil discoloration?
 
Not an expert on these bigger engines, but that temp sounds OK here. I'd be tempted to decrease my oil change interval by quite a bit to see if you might be able to clear it up. Maybe do a couple of 20 - 50 hour changes?

How long did it take you to put that next 80 hours on? Are you changing once a season, even if you don't reach the suggested hours for a change?
 
The oil was changed at 20 hr in June, 2019. Because of Covid, the boat has pretty much been laid up since March, 2020. The engine has only seen 10 hr since then. So the oil has been in there for a while.
 
Well, at 100 hours, the rings and valves have not likely been completely seated. When I got my new 225 back in 2008 and took it in to the dealer for it's first 100 hour. The oil was darker than I thought it should be. The dealer told me I was "babying" the engine too much. I needed to run it hard to get everything properly seated.

I took that advice and in subsequent oil changes, the oil seemed very normal in color and wouldn't start darkening up significantly until 50 hours or so.

As for the temperature - I'm not sure where your gauge is sensing the temperature. On my 225, normal operating temperature at the manifolds should be around 160 F and normal operating temp at the top of the block should be about 190 F.
 
I used Honda oil at the 20 hr service. The guy who did the 100 hr works mostly on Hondas and said that the oil is usually still a light color in a new engine.

I broke in the engine hard. It replaced a Yamaha F250 that made oil like crazy for 10 years. I attributed that the gentle break-in that I did. So I ran the Honda at full throttle for a minute out of every 10 minutes during the second hour of operation. It saw plenty of full throttle bursts over the first 10 hr. The oil level was right at the full line after 20 hr and the oil was still very light colored. So the discoloration took place between 20 and 100 hr. I cruise between 4500 and 4700 rpm. I did quite a bit of trolling over the last 10 hr.
 
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