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2006 Yamaha 115 "Making Oil"

 
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spd



Joined: 19 Sep 2016
Posts: 16
City/Region: Mukilteo
State or Province: WA
C-Dory Year: 2007
C-Dory Model: 23 Venture
Photos: spd
PostPosted: Fri May 12, 2017 1:00 am    Post subject: 2006 Yamaha 115 "Making Oil" Reply with quote

First of all I would like to introduce myself to you all. This forum has saved me countless hours and helped me considerably in getting to know and diagnosing issues on my new-to-me 2006 Venture 23. One of the problems with such comprehensive archives is that I can find solutions to most of my issues by just searching! Like many of you it seems, I have until this point always been a sailor. However, my wife and I decided that a C-Dory was much more practical for how we wanted to spend our time (a little bit of a “the journey is just as important as the destination” mentality mixed with the attention span of two young kids).

We purchased the boat last October with ~430 hours on the 2005 Yamaha 115. When we bought the boat we were aware that it had some motor problems, which we thought were mostly ethanol related. Well, after working on the fuel system, cleaning and replacing several injectors, and replacing a stuck thermostat, the motor seems to be running just fine. We have put about 40 hours on the motor since October. Since we ironed out most of the motor problems (I say most due to issues we still have with engine stalling when quickly shifting and throttling—a problem for another day….), I have become somewhat complacent about checking the motor oil level.

While I was working on the boat today I checked the oil level, and to some shock I discovered it was overfilled by several inches! After some searching, I am thinking that this may be “blow-by”—the motor “making oil” by gas mixing into the oil. (The oil is not milky.) There is some information out there that suggests that engine lugging can cause this. Right now my top RPM is about 5000. I realize this is low. I am currently running a SS 17P prop, and have an aluminum 15P that I am going to install. (The Prop Shop in Mukilteo suggested I try a 15P to see how that helps, instead of going straight to a 13. They will let me test it out and return if it doesn’t work.)

My questions for everyone is whether you think I can solve my extra oil issue by merely changing the prop, especially since I just replaced the thermostat? Do I need to be concerned about what degree thermostat was installed? What else do I need to look into?

Thanks in advance for the help.

Sean
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jennykatz



Joined: 15 Dec 2003
Posts: 1678
City/Region: naples
State or Province: FL
C-Dory Year: 2006
C-Dory Model: 23 Venture
Vessel Name: Little Treasurer
Photos: Jennykatz
PostPosted: Fri May 12, 2017 1:40 am    Post subject: cc 23 Reply with quote

We have the same boat and had the same engine f115 yamaha 2005(1100 hours ) I sold the motor and bought a new merc 115 CT bigger gearcase
We used a s/s 13 1/2 by 15 pitch we woulld get about 5400-5600rpm out of it If top WOT is 5000rpm that is to low .

With the merc 115 we have a 14 1/2 by 17 pitch i get about 5600and 32 mph with 2 persons in boat . and about 4mpg
Good Luck with Yamaha I loved the yami but the merc actually is quieter and handles better .Jim

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retired 8/08 from UAL, still working pt tm
Duck c-22 cruiser sold 6/23/08
06 Venture Cruiser with merc115CT
00 cd16 cruiser honda 40 sold 3/12
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AstoriaDave



Joined: 31 Oct 2005
Posts: 994
City/Region: Astoria
State or Province: OR
PostPosted: Fri May 12, 2017 3:49 am    Post subject: Reply with quote

Sean, I knew of an engine making oil, later traced to a hole in the diaphragm in his fuel pump. His was older, and just a 50 horse, but I cannot recall the make. His ran rough, kept stalling. Fixed by replacing the fuel pump, I think.
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Dave Kruger
Astoria, OR
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thataway



Joined: 02 Nov 2003
Posts: 20778
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Fri May 12, 2017 11:55 am    Post subject: Reply with quote

Common complaint on the 115's (I had one, but it was OK).

Rings not seated, carbon build up, or not properly broken in. If this the case, Dealer needs to de-carbon.

Lugging, as you suggested, Certainly drop down to 15"--the aluminum will flex more than the SS, and hopefully you will get 5500 RPM.

Thermostat bad--you replaced. As I remember the stock thermostat was 140--if it still makes oil, then go up to 160 or 180. Put in hotter plugs.

Bad ECU

Fuel pump Diaphragm issue

All relate to dilution with gasoline. Oil analysis is helpful here.

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Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
KA6PKB
Home port: Pensacola FL
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BrentB



Joined: 15 Jul 2006
Posts: 4419
City/Region: Greenwood
State or Province: IN
Photos: BrentB
PostPosted: Fri May 12, 2017 3:03 pm    Post subject: Reply with quote

I am going with bad thermostats. Smile
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Brent Barrett
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