Sheen in water

boater2065

Active Member
Jul 30, 2018
222
Everett, WA
Boat Info
Searay
Engines
merc
Hi all, been noticing this sheen in the water lately while running the engine (photo attached). I had the mechanics scope the engine and they said everything looks fine (fuel pressure, computer tested, not running rich, etc). While I trust their word, this doesn't seem normal.

PXL_20201217_204334788.MP.jpg
I wondered if the trim tabs were leaking ATF, so before running the engine I put the trim tabs up and down a handful of times. I never saw any sheen. Then I fired up the engine and immediately the sheen appears. I brought the engine up to temp and shut it off. The photo attached is after the engine was off.

Anyone have any ideas what this may be caused by?
 
You could have a leaking oil or trans cooler. Have you checked your fluids for water?
 
Does it always leave this sheen, or is it on startup? After you cruise and come back to your slip, are you still generating a sheen?
 
Does it always leave this sheen, or is it on startup? After you cruise and come back to your slip, are you still generating a sheen?
Yes, after i go cruising i still see a sheen in the water. I took it for a cruise a week or two ago for an hour or so hoping it would go away, but pulling back into the slip i still saw the sheen.
 
Top suspect would be the oil cooler (if the 5.7s have one). This was the exact problem I had on my 8.1 motors. The oil pressure is higher than the raw water pressure, so luckily you won't get water in the oil.
 
How's your outdrive oil reservoir level? If the seals in the outdrive start to go, oil can leak from from the bottom end of the drive. Also check your outdrive hydraulic trim pump. It's a unit separate from the engine and has it's own reservoir its possible that one of the rams is leaking.
 
Stop by your fuel dock and get a couple 3M oil absorption mats and when you see the sheen, throw one or two on top and retrieve. Check to see what color it is. Black/Brown might be engine oil, red ATF. I think drive lube is greenish blue (?).

Might help pinpoint the source.
 
How's your outdrive oil reservoir level? If the seals in the outdrive start to go, oil can leak from from the bottom end of the drive. Also check your outdrive hydraulic trim pump. It's a unit separate from the engine and has it's own reservoir its possible that one of the rams is leaking.
Thanks for the tips. This fall i had the outdrive serviced so they would have topped off the gear lube. I'll check the level of that next time i'm there.

Regarding the trim pumps...if one of the rams was leaking, would it only leak when the engine is running? I see no sheen on the water if i come to the boat cold. Only once i start it up i see the sheen.
 
Stop by your fuel dock and get a couple 3M oil absorption mats and when you see the sheen, throw one or two on top and retrieve. Check to see what color it is. Black/Brown might be engine oil, red ATF. I think drive lube is greenish blue (?).

Might help pinpoint the source.
Appreciate this tip, great suggestion that i will likely try
 
Thanks for the tips. This fall i had the outdrive serviced so they would have topped off the gear lube. I'll check the level of that next time i'm there.

Regarding the trim pumps...if one of the rams was leaking, would it only leak when the engine is running? I see no sheen on the water if i come to the boat cold. Only once i start it up i see the sheen.
Sure, it's possible. But the rams only activate when you are raising or lowering the drive unit - that's when there is pressure being adding to the trim rams.

Given that, it would seem like the leak would be from something that's under pressure only when the engine is running. That would be seem to point more toward engine oil (coming from the exhaust), oil / transmission cooler, or drive oil.
 
Sure, it's possible. But the rams only activate when you are raising or lowering the drive unit - that's when there is pressure being adding to the trim rams.

Given that, it would seem like the leak would be from something that's under pressure only when the engine is running. That would be seem to point more toward engine oil (coming from the exhaust), oil / transmission cooler, or drive oil.
For sure. I didn't trim the engine at all when I fired it up and took that photo. I'm leaning more towards some of the other options mentioned by you and a few others. Checking fluid levels and finding out the color of the sheen will be my new starting points.
 
Hi all, been noticing this sheen in the water lately while running the engine (photo attached). I had the mechanics scope the engine and they said everything looks fine (fuel pressure, computer tested, not running rich, etc). While I trust their word, this doesn't seem normal.

View attachment 96443 I wondered if the trim tabs were leaking ATF, so before running the engine I put the trim tabs up and down a handful of times. I never saw any sheen. Then I fired up the engine and immediately the sheen appears. I brought the engine up to temp and shut it off. The photo attached is after the engine was off.

Anyone have any ideas what this may be caused by?
 
Stop by your fuel dock and get a couple 3M oil absorption mats and when you see the sheen, throw one or two on top and retrieve. Check to see what color it is. Black/Brown might be engine oil, red ATF. I think drive lube is greenish blue (?).

Might help pinpoint the source.

I ran the engine for a bit and put an oil mat on the sheen for a few minutes. I have attached that photo here. this must be engine oil, I take it by the color?
PXL_20201221_212600402.jpg
 

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