Mystery oil leak

1132MM

1132MM

Member
Aug 1, 2010
187
Wantagh, NY
Boat Info
2004 Sea Ray 280 Sundancer
Engines
Twin 4.3 Liter Mercruiser w/Alpha One Gen 2 Drives
I have a 2004 280 Sundancer twin 4.3 L MPI. I’ve owned the boat for the last 4 years and always removed the oil using suction through the dipstick. The past year I found the oil drain hoses that come out of the bilge plug and used those for the first time. The starboard engine is fine but I notice the port is losing oil while the engine is not in use. There’s also a lot of oil in the bilge water. I’m going to put oil diapers down and see where it’s dripping from. Looking for any other suggestions. Thanks.
 
Like you, I extract it from the dipsticks and never use the drain hoses. I can see where they are though.

Where are the ends of the hoses now? Are they down near the bilge drain plugs? If so can you pull them forward and see if they are leaking?
 
The 4.3 is notorious for developing oil leaks where the plastic timing cover meets up with the oil pan. Mine has leaked there for years, it a small seep, never have to add oil, just keep a diaper in the bilge and wipe it off occasionally. Have to pull the engine to fix it, and the design is bad so it will likely leak again.
 
I had a hidden leak once on the out board valve cover. Knew something was leaking, but couldn't find it for years. Then one day accidently put my hand there and bingo, found the leak.
 
Thanks for the replies. I will check all these areas.
 
If you are losing oil while engine is not in use, it is the oil pan (not uncommon) or something attached to it BELOW the oil level.

An oil containing item leaking like, the oil filter or oil cooler can also leak down oil, but low level won't be noticed until after a start up refills them.

Valve covers or timing chains don't leak unless engine is running, since static oil level is below that..
 
The first SR we owned was a 2006 260DA. Kept noticing a minor amount of oil in the bilge. Looked, but never located the source. Finally figured out it was happening when engine was not running as well as when it was running. Amount slowly increased over a couple of months. Narrowed it down to the oil pan. Found the bottom of the oil pan had several pin holes in it. Engine pulled and pan replaced. The bottom of the old pan was basically rotten.

Bennett
 
Get a cheap handheld mirror with a handle and a good flashlight to look under the engine, it has saved me lots of times.

I also have used strategically placed oil absorbent mats held in place with zip ties or tape to help narrow down the leak location. I had a seep from an oil cooler hose that i found when the leak appeared on the mat.
 
Thanks for the replies. I am focusing on the oil pan right now. I have diapers down hopefully to pinpoint exactly where its coming from. Never had a problem until I used the drain hose last November. I think by moving the hose and trying to orient back towards the bilge drain plug I might have loosened the connection. Hopefully, I didn’t crack the hose.
 
I had the same problem an it was the oil pan.
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