300 Yamaha, 'Milky' Oil in Lower Unit Lube/Oil

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A

Andy

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Our 2014, Yamaha 300 UCA has at times gotten some water ('milky' oil) in the lower unit lube/oiI. I've seen it a couple times over the years, when I've changed the L/U oil. So I started changing it at 50 hours instead of 100 hours. (there is about 950 hours on the motor now). When I started changing it at 50 hours, the oil looked real good; no 'milky' oil. A couple time when I changed it around 100 hours, it looked 'milky'; as shown in this video;



I've pulled the prop a number of times. Only once was there a tiny, few pieces of fishing line, easily removed. All other times, nothing; no fishing line......
I've read that this particular Yamaha engine has had issue with the seals down there in the L/U, and that a little water in the L/U oil is expected, and is not an issue. The Yamaha manual even states 10% is 'normal' and not an issue (I don't like ANY water leaked there, and how would I determine 10% !) .... I would love to hear the opinion and expertise from the ClassisParker gurus.... I troll a lot around 7-8 mph. Does running at low rpm cause the L/U seals not to 'seat' properly. Even when I troll for hours, I still run it at 4300-4400 rpms for 45 - 60 minutes on the way home.... Then to 5000+ for a few minutes.... I'm wondering if trolling at 7-8 mph is not good for a 300 Yamaha?
 
Brent said:
I dont know if me , I would have LU pressure and vacuum tested. I assume the LU fill and drain screws washers are changed ?
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Yes, I change the washers/seals every time I drain it.... I'll look into having it vacuum tested or I'll learn how to do it myself... Thank you!
 
LOL No No....Not from a floatating platform.....You may as well do a full waterpump replacement ...They will be right there anyway.
 
I have a 2015 2520XLD, F300UCA bought new. From day one I had issues regarding lower unit oil. After the first 25 hours check I found out after the fact the mechanic used syn Etech lower unit oil which is a big no-no as it states in owners manual never use syn lower unit oil. I am in my 6th season now. My suggestion to you is to change all the seals in the lower unit, shift shaft,prop shaft etc. Two years ago my mechanic changed them and it improved but wasn't perfect. Last winter Yamaha changed the shift shaft (or cam shaft) seal which was supposedly causing the issue. Last winter my mechanic changed it again with the new part. Last month when I did my mid season maint the oil came out of the lower like it was brand new, the best I ever seen it so I would start there. My oil used to come out greyish looking.
I now have over 2000 hours and last season after using Yamaha synthetic oil since new I performed mid season maint and was surprised to find the engine oil was close to 3 quarts low. Thinking the mechanic didn't put in enough oil I added oil and finished out my season. When we pulled the boat my oil level was again almost 3 quarts low.
Since the synthetic oil was becoming so expensive I decided to change over to regular Yamaha 10-30 4M oil.
After one month after launch this spring and little use I burned a quart. After that I have been monitoring the oil very closely. Everything was good until a couple weeks ago. After running 2 offshore trips (approx 60 miles each way) I checked oil and again over 2 quarts low. The oil was barely touching the tip of the dip stick.
Tomorrow my mechanic is go to perform a de-carb on the engine and see if that improves the oil burning issue. There hasn't been any sheen or visible signs of where the oil is going so I am assuming it is getting blown past the rings. I also had called Yamaha and spoke to a tech and after explaining the story a de-carb was his first suggestion.
I know I have a lot of hours but I perform all necessary procedures according to my owners manual so I feel I should be able to get 4000 plus hours before investing another 24K on a new 300.
 
Lucky John said:
I have a 2015 2520XLD, F300UCA bought new. From day one I had issues regarding lower unit oil. After the first 25 hours check I found out after the fact the mechanic used syn Etech lower unit oil which is a big no-no as it states in owners manual never use syn lower unit oil. I am in my 6th season now. My suggestion to you is to change all the seals in the lower unit, shift shaft,prop shaft etc. Two years ago my mechanic changed them and it improved but wasn't perfect. Last winter Yamaha changed the shift shaft (or cam shaft) seal which was supposedly causing the issue. Last winter my mechanic changed it again with the new part. Last month when I did my mid season maint the oil came out of the lower like it was brand new, the best I ever seen it so I would start there. My oil used to come out greyish looking.
I now have over 2000 hours and last season after using Yamaha synthetic oil since new I performed mid season maint and was surprised to find the engine oil was close to 3 quarts low. Thinking the mechanic didn't put in enough oil I added oil and finished out my season. When we pulled the boat my oil level was again almost 3 quarts low.
Since the synthetic oil was becoming so expensive I decided to change over to regular Yamaha 10-30 4M oil.
After one month after launch this spring and little use I burned a quart. After that I have been monitoring the oil very closely. Everything was good until a couple weeks ago. After running 2 offshore trips (approx 60 miles each way) I checked oil and again over 2 quarts low. The oil was barely touching the tip of the dip stick.
Tomorrow my mechanic is go to perform a de-carb on the engine and see if that improves the oil burning issue. There hasn't been any sheen or visible signs of where the oil is going so I am assuming it is getting blown past the rings. I also had called Yamaha and spoke to a tech and after explaining the story a de-carb was his first suggestion.
I know I have a lot of hours but I perform all necessary procedures according to my owners manual so I feel I should be able to get 4000 plus hours before investing another 24K on a new 300.
Click to expand...
Thank you, this is helpful information!... I wonder how many other Yamaha 300 owners are having this issue? Is it the same with all Yamaha 300's?
 
Brent said:
No I don't I don't recall the full FB post and sometimes these posts lack details, facts and content basically letting off steam. Check with Andy at SIM in his Band of Brothers website. Hull truth or Wayne Shoup on the Yamaha outboard FB page. He and Warthog think the same.
Click to expand...
I first learned about SIM Yamaha from ClassicParker and that's where I've gotten all my parts, 100-Hour service kits, motor cover, plugs , T-stats, anodes/zincs, etc ever since we got this Yamaha... I've also contacted Andy (he has an exceptionally good first name) a number of times; he is a lot of help, as are the others at SIM.... (yes, this was a shameless plug!)...
 
Andy said:
Thank you, this is helpful information!... I wonder how many other Yamaha 300 owners are having this issue? Is it the same with all Yamaha 300's?
Click to expand...
Seems like I am not alone, in fact a buddy of mine blew his lower 3 weeks ago, he had a pair of 300's on his regulator. For some reason they only changed the seal on one engine and it was the other one that blew, it actually blew a hole in the side of the lower unit. It took him about 2 weeks to get a new lower. (under warranty). My mechanic also tells me he has seen my issue in other 300's so it seems to be a common issue. I'm getting my decarb done today so I'll keep you posted. Hopefully it restores some of my RPM's back as it seems I lost a little. Used to be able to turn 5700 but lately can't hit more than 5400
 
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