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  #1 (permalink)  
Old 02-29-2012
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Join Date: Feb 2012
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Default GAS IN OIL 150 four stroke?????????

It is amazing to me how many people have posted on this subject, and nobody really has a cure. Unfortunately, we just bought a boat in Costa Rica with twin LF150TXRD's. The engines only have 890 hrs on them, and the survey came back perfect, perfect compression, and no fault codes. Before we ran the boat we did the full 1000 hr service, plus had the injectors cleaned. After 50 hrs of service, both motors have gas in the oil, about 1 inch above full. Everything that I've read is contradictoy, and our local Yamaha dealer in Tex. says they have'nt run into this proble......B.S.! It seems like Yamaha says everyone isn't running their engines hard enough, but........that may also happen if you are over wheeled????????????? Don't idle too much!!!!! Why would anyone put one of these motors on a fishing boat? Some say use a hotter thermostat, but some say not to. As much as I've read I'm more confused than ever. Has anyone actually cured this problem? Thanks
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Old 02-29-2012
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Location: Lake Placid, Fl
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If engine wasn't properly broke in when were new then rings don't seat and causes problems later on, engines need to be propped on high side of rpm range(5000-6000), thermostats need to be in good working order and thermo sensors tested to see if working properly(cold engine runs richer than warm engine), bad diapram in fuel pump or faulty injectors can also cause it.
Do a leak down test on cylinders to see pressure is leaking past rings.
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Old 02-29-2012
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Join Date: Jan 2011
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Default It Fixed my 115 hp

had the same problem on my 115 4-stroke hp. Talked to a guy who told me about this "making oil" thing/problem. Did a lot of idling at low speed in cold water. He said that the thermostat was probably stuck open making it run cold/rich. Anyway, I pulled the thermostat and sure enough, it had some corrosion and gunk on it that kept it open. I changed it out with a new one, haven't had a problem since.......
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Old 03-01-2012
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Join Date: Feb 2012
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We re-checked the injectors yesterday they were fine, inspected fuel pump diaphrams, we will change the thermostats tomorrow. The boat was built for and brought down here for the CEO of Contender, you would assume that they did a proper break in. The Captain that used to take care of the boat, and that no longer worked for the people when we bought it, said that they never had that issue and all of the maintance was done by the book. As far as the props go my buddy has the same exact boat except he holds 75 more gallons of fuel w/more hours, and the same exact props, w/no issues. It also turns out there is another boat here w/225 4 strokes having the same problems.......both engines. It also seems strange that both engines would have the same amount of gas in the crankcase.
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Old 03-01-2012
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They have 122 deg. thermostats in them, I noticed some recommend a 144 deg thermostat. What do you think about that?
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Old 03-02-2012
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Use 67F-12411-01-00 60c thermostat in it
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Old 03-05-2012
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Join Date: Dec 1969
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What RPM are you turning WOT?
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