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danjo

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My 2006 Yamaha 115 hp is making oil. I installed a new low press. pump and didn't help so I made a block off plate and bolted to valve cover and installed an elect. fuel pump and this didn't correct problem. Compression is 141 - 152 - 151 - 157. Can anyone suggest what I should do next, thanks.
 
The F115 is notorious for making oil. I know this will sound dumb, but change your thermostat. I bet it is stuck open. basically the cause is the thermostat sticks open (or poppet valve) and the engine is over cooled. when it is run cold like this, the rings do not seal properly and the cylindrs become "glazed". basically this allows raw fuel to go past the rings and into the oil.

Once you change the thermostat and get it back to running at normal operating temp again, run it pretty hard for a little bit. AKA WOT under load This will help to generate heat and the rings will seal again and all will be well.

Had this happen twice with my 115 and once with a 90. all 3 times were stuck open thermostat.

Another thing that can cause this is excessive idling or putting around. basically has the same effect.
 
Also.....I believe the stock thermostat for the 115 is 50*C whereas most of the other motors are 60*C. never gotten a good answer as to why the 115 is lower. Some people have put the 60*C sts into their 115 with no problem. I myself have done it for a short time with no issues. Just throwing that out there...
 
slimbo3006 said:
The F115 is notorious for making oil. I know this will sound dumb, but change your thermostat. I bet it is stuck open. basically the cause is the thermostat sticks open (or poppet valve) and the engine is over cooled. when it is run cold like this, the rings do not seal properly and the cylindrs become "glazed". basically this allows raw fuel to go past the rings and into the oil.

Once you change the thermostat and get it back to running at normal operating temp again, run it pretty hard for a little bit. AKA WOT under load This will help to generate heat and the rings will seal again and all will be well.

Had this happen twice with my 115 and once with a 90. all 3 times were stuck open thermostat.

Another thing that can cause this is excessive idling or putting around. basically has the same effect.
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I have replace the thermostat with the OEM replacement and checked it again this summer to make sure it was not stuck open. I have tried everything to seat the rings by running it at WOT after sprinkling Bon Ami (sparingly) in the intake to scuff up the cyl. bores. Engine starts right up, idles and runs perfect all the time. Taking it to a boat mechanic next month, hope they can find something.
 
slimbo3006 said:
Also.....I believe the stock thermostat for the 115 is 50*C whereas most of the other motors are 60*C. never gotten a good answer as to why the 115 is lower. Some people have put the 60*C sts into their 115 with no problem. I myself have done it for a short time with no issues. Just throwing that out there...
Click to expand...
I found a 60 Degrees Thermostat Part # (67F-12411-01) for Yamaha F75 F80 F90 F150 VF250 Outboard. Going to replace my thermostat with the higher opening 60 degree. Thank you for your response!
 
danjo said:
I have replace the thermostat with the OEM replacement and checked it again this summer to make sure it was not stuck open. I have tried everything to seat the rings by running it at WOT after sprinkling Bon Ami (sparingly) in the intake to scuff up the cyl. bores. Engine starts right up, idles and runs perfect all the time. Taking it to a boat mechanic next month, hope they can find something.
Click to expand...
Appreciate your help, thank you!
 
danjo said:
I found a 60 Degrees Thermostat Part # (67F-12411-01) for Yamaha F75 F80 F90 F150 VF250 Outboard. Going to replace my thermostat with the higher opening 60 degree. Thank you for your response!
Click to expand...
Yea a thermostat for an F90 is what was in my F115 briefly. ran it pretty hard for a few weeks this summer with no issues.

might give Yamaha Ringfree a try. It is a little pricey..(like most things Yamaha) but a lot of people really say it works. I ran it through mine after I had issues with a stuck thermostat and making oil... I still run it through all of my engines periodically. especially my 2 strokes...
 
racerone said:
You sprinkled an abrasive cleanser into a running engine ?---Why?
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We did this to our sprint car engines when we were running chrome rings years ago to help seat the piston rings. chrome rings were very hard to get seated but were used because of the dust and dirt conditions they were exposed to. (Sparingly of course)
 
slimbo3006 said:
Yea a thermostat for an F90 is what was in my F115 briefly. ran it pretty hard for a few weeks this summer with no issues.

might give Yamaha Ringfree a try. It is a little pricey..(like most things Yamaha) but a lot of people really say it works. I ran it through mine after I had issues with a stuck thermostat and making oil... I still run it through all of my engines periodically. especially my 2 strokes...
Click to expand...
I was running pure ethanol-free gas 91 octane and Sea Foam and last year I switch to 89 ethanol blend (regular pump gas) with the Yamaha Ring Free Plus and experienced no change.
 
Sounds like you could possibly have a sealing issue with the rings/cylinders or such then.. Compression #'s arent bad although #1 is lower than the others...

keep us updated if the 60* T-stat helps any...
 
slimbo3006 said:
Sounds like you could possibly have a sealing issue with the rings/cylinders or such then.. Compression #'s arent bad although #1 is lower than the others...

keep us updated if the 60* T-stat helps any...
Click to expand...
Thanks everyone, I will keep you informed on the 60*c T-stat and what marine tech. says.
 
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