Merc 40HP - Oil in Prop!

[JEllis]

Hi,<br /><br />I am only new to power boats and I've just had my 40HP Merc outboard serviced for the first time. I've taken it out twice since the service and after kicking it over it is leaking quiet a bit of oil from the prop area and also a hole in the side of the shaft (sorry for the high tech talk! ))... From reading some of the topics in this post, it seems that this is quiet normal for Merc OB's? It is blowing black smoke and I am sure there is no water in the oil. What should I do about this? Is it worth draining some of the oil out? (I've read that this may stop the problem) Also, is this excess oil causing any damage to my engine.<br /><br />Any advice would be greatly appreciated.<br /><br />Thanks

 

[Moody Blue]

Re: Merc 40HP - Oil in Prop!

Your post is a little confusing but I will try to help as much as I can. You don't indicate the color or consistancy of the oil so its hard to pin down the source.<br />Leaking any amount of oil, let alone quite a bit, is not normal so something is wrong. If oil is leaking around the prop area the prop shaft seals are probably leaking. Oil coming out the side of the shaft may indicate either the diveshaft seals or shift shaft seal may be leaking. <br />Removing oil from the lower unit to stop a leak is not the solution unless you have extra money to spend on a new lower unit. Check the oil level in the lower unit and look for water contamination.

 

[AMD Rules]

Re: Merc 40HP - Oil in Prop!

As usual, Rod is correct. Unless the lower unit was intentionally overfilled there would be no benefit to reduce the level at this point.<br /><br />Both of my motors drool oily residue (exhaust/fuel/oil/water) out the center of the prop after I have run them in a barrel, or on muffs. Was yours leaking oil after a lake test, or a land test?<br /><br />Oil out the side of the lower unit indicates a possible shift shaft and/or drive shaft seal,as Rod already mentioned.<br /><br />Good luck, and let us know how you make out.

 

[JEllis]

Re: Merc 40HP - Oil in Prop!

Thanks for the reply Rod and AMD. <br /><br />Rod... The oil is black in colour and fairly thick in consistency (i.e. looks like new oil straight from a tin? I hope this answers your question!<br /><br />AMD.... It is leaking oil both after a land test (with muffs) and after taking it out... (it left a oil water mark on the transom...<br /><br />Considering this has only been happening since I had the engine serviced, do you think it is worth me taking this back to be looked at again?<br /><br />What do you think I should do from here????

 

[Moody Blue]

Re: Merc 40HP - Oil in Prop!

Sounds like unburnt oil/gas combustion product as mentioned by AMD Rules. The stuff tends to build up in the exhaust tube especially after extended periods of idling. Why it just started to happen, couldn't say. What service work was performed on the motor? Couldn't hurt to take it back and ask a few questions.

 

[JEllis]

Re: Merc 40HP - Oil in Prop!

Thanks Rod.<br /><br />The 12 Month 100Hr service was done. <br /><br />I can't understand why this has just started to happen since getting the service. I will take this back to get them to have another look at it......<br /><br />Thankyou for your help. Much appreciated.<br /><br />Cheers<br />Justin

 

[Moody Blue]

Re: Merc 40HP - Oil in Prop!

Good luck and post back with any findings.

 

[fishingdan]

Re: Merc 40HP - Oil in Prop!

Just for reference, I had a similar problem. Right after the carbs were "professionally" rebuilt, I had a similar situation. While in the water, the engine looked like it was leaking a small amount of fuel and the transom would blacken after a few hours of idling. When parked in the driveway after the outing, I too would see the dark black oil residue dripping out of the prop/exhaust. <br /><br />It turns out that the professional didn't tighten the bowl of the lower carb and it was leaking fuel. Since the bowl was literally loose, the engine wasn't running right at idle. It was clearly running way too rich. Removed carb, reset the float and the problem was corrected. <br /><br />On my engines at least, lower unit leaks tend to be more true dark amber oil color or a dark greyish sludge if there was water in the low unit.<br /><br />Hopefully it is an easy fix<br /><br />Dan