Chris Wilson
Cadet
- Joined
- Jul 7, 2002
- Messages
- 20
We have a 1991 Evinrude 40 HP OB (VWE40TLEIA) which leaks a light brown oily foam after use. Most of the time it comes out a drain opening at the front edge where the lower and intermediate casing are joined. However, occasionally, we have seen it coming out of the prop hub area. Which area it comes out seems to be more of how the engine is tilted over time
<br /><br />Recent changes to the engine include a rebuilt power head (purchased from Southwest Marine), which seems to be performing nicely. We went through at least a ten-hour break-in period at 25:1 (we disconnected the oil injection after the original power head failure). We are now running at about 40:1 and are working our way back to 50:1.<br /><br />We drained the lower unit oil a couple of times because of this foaming and it looks like it came right out of the container really clear. We also confirmed the oil type we should be using with a local Evinrude dealer and are using the recommended manufacturer brand and type. We dropped the lower unit and looked up into the intermediate casing and could see the foam fairly far up in the unit. After much hypothesizing, we figured it probably stuck to the sides at the water line inside the cavities when the engine was in the water, but it still did not reveal the source.<br /><br />The recent use is mostly barrel testing in the driveway and trolling speeds for Salmon on the Great Lakes and the engine has run flawlessly.<br /><br />Even though the inside the lower unit oil looked good, the top of the water pump, shift housing and surrounding areas had all this oily foam. As a result, we decided to change some of the lower unit seals, and did so on both the drive shaft and shift rod. We addressed only those seals since it appeared that the oil was essentially on top of the lower unit and not in it as far as we could tell. As a result, we did not touch the seals for the prop drive. Obviously, changing these top seals did not seem to help but at least it made us feel better
<br /><br />Since the engine seems to be running nicely we are becoming less concerned, but not unconcerned, and are at a loss to explain the phenomenon. However, we are thinking that the heavier oil mix and low speed operation may be introducing more oil into the exhaust than standard and, being lighter than water, the oil is becoming trapped in some of the cavities in the intermediate casing and then leaking out once the boat is out of the water. However, it is just a guess.<br /><br />A second theory is that some fuel/oil mix is leaking from the carbs and being caught by the drain hose, which seems to return it to the power head. If this recovery is really just a direct path to the intermediate casing/lower unit we thought this might also be a source, if the carbs are leaking excessively. However, I would have thought that this drainage would be sent to the interior of the power head and eventually burned off. <br /><br />The amount of foam does not seem to be great. The flow from the drain hole I mentioned earlier might create a drop on the concrete about the size of a half dollar or silver dollar and then seems to stop.<br />Any thoughts or feedback on our theories or other suggestions identifying other possible causes would be greatly appreciated.<br /><br />By the way, this site is awesome. Found and ordered my power head here
and the advice and experiences in the forum are outstanding