Yamaha 4 stroke "making oil"
 

I changed the oil and filter in my f60 over the winter and added the 2.6 qts. of oil. Several checks of the dipstick to be sure the level was right. Returned from first trip out...checked oil...several times ....dipstick showed oil level waaay above hatched area. Drained it out and it measured it thinking it would be more than specs but it wasn't over. The oil has a darker color than it should being only a few hours use and faint gas smell??? Read up on possible cause and solutions.

Anyone have similar experience?

My yamaha dealer says I might have been running "cold" and possible that my engine wasn't getting up to temp. causing unburnt fuel in the cylinders to drain past the rings and into the crankcase.

I spent a lot of my last trip at trolling speed...no wake zones...shallows etc. and only one short run at full throttle. Thermostat doesn't appear to be stuck but had some corrosion so changing that out. I flush engine after every trip. Brought them a sample of the oil I drained and they confirmed it had odd color and smell.
I'll add new oil and thermostat and see what happens.

Next trip i'll make sure to run at mostly cruising speed

I've seen it in some older John-Zuki motors- it was years ago and there was some kinda ring problem. they did a "leak-down" test to confirm

I was told the wrong prop (resulting in overloading the engine for a given rpm) can also reportedly contribute to this.

I changed out a dinged prop a while ago with one of a different diam and pitch.....never felt quite right....
Thanks ....I'll look into that

Look hard at that. Different diameter and pitch seems extreme unless you were having issues
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I've never been sure what the correct prop for my boat is.
I had originaly bought an 11" x 17 pitch...but the yamaha mechanic that rebuilt the carbs said it wasn't right for the job. He exchanged it for a 11 5/8 ' x 11 which worked fine...until I dinged it on a rock.
Went back for a replacement and that size was out of stock....was told that a 10 5/8' x 12 might be close enough? Having some doubts about that now.

would Yamaha be able to tell you what the stock prop would be? I've found that even the same size by different manufacturers will effect performance. I increased the diameter by .25 inches this year and my boat acts significantly different - for the better :)

Make sure at wot you are at the top of the recommended rpm range.
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Yamaha specs for my engine says 5000-6000 rpms....ill check on full throttle rpms again next trip
....pretty sure it is much lower than 6000 with this prop.
Thanks
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Hitting the max rpm's for the engine is not the only way to judge a prop. But if you are otherwise happy with it, for engine health, it is MOST important.

I am convinced now, that the problem resulted from having my engine in gear, but at idle, 7500 rpms, for an extended period of time ...unburned gas in the cylinders leaking past the rings and getting into the crankcase. I changed oil and made two trips since and no more problems. Should have known better...thats what trolling motors are for.:1poke:

all 4 stroke engines can "make" oil under the right conditions when they idle a lot ( that includes cars and trucks that drive in slow moving traffic a lot)... especially in cold weather.. it's one thing that ATV manufactures warn users to keep an eye on when used in cold weather ... and as other's have suggested.. prop selection can make a difference as can a thermostat that is running "#^&#^&#^&#^&.. bottom line is if you own a 4 stroke outboard and troll a lot... you will need to increase your oil change intervals.. the perfect outboard has not been invented...YET ,they all have their faults.. but for me..I love the smell of 2 stroke oil in the morning...PS... I have always recomended changing the thermostat every 2-3 years when you change the water pump... it assures that it always come apart and is cheap insurance... they work together, why not change them together.

as a side note... look into power tech propellers.. they make a size and style prop for every need.... you can also contact Ken at prop gods.. the guy is real good at what he does.. recommending propellers for "troubled" boaters.

Thanks...appreciate your advice....
I did change out the thermostat when I changed the bad oil.
Serious question....I thought that the thermostats job is to keep the engine from overheating but can a stuck one keep the engine to cold?
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Bob, I'm no marine mechanic....nor would I ever pretend to be one...but when I owned an inboard, (Volvo/Penta)....both marine mechanics that serviced her had me convinced that she didn't need a thermostat.
After removing it, the boat ran much better.....I'd imagine that if they come with a thermostat, they call for it...but I'm not sure if it's truly NEEDED?

Not sure how I/B's vs. O/B's compare when it comes to requiring a thermostat?

Just sharing my experience...

Thanks Gilly......I'm no mechanic...but as with everything I own...I prefer to learn and understand how and why things work or don't work.
I really dont like paying someone to fix problems for me, especially after seeing the kind of work some so called professionals do. I built my home 40 years ago and have done all the maintenance, including plumbing and electrical. I work with "so called" pros everyday and can tell you I dont want them working on my house.

Read a few more articles about outboard thermostats, and at least I'm getting a better understanding, and that apparently a constantly open one can cool the engine too much, and cause unburned fuel problems and carbon buildup, especially at low speeds.

https://www.boatingmag.com/boats/und...nes-thermostat

The problem with troubleshooting is it keeps you on land. I would ask around and find a mechanic who is every bit as competent at his craft as you are Bob. I have had a couple that I swear by. I am not saying they don't make mistakes but they get me up and running in short time. He beginning of summer is not the best time to be high and dry,or learn a craft that others have been fine tuning for 40 years
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I agree Chris...i had a professional rebuild my carbs 5 years ago.....just trying to learn the simpler things myself.
im not having any problems at the moment .running great !
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When i started building my boat, I was completely confident in my woodworking abilities, but when it came time to do the rigging of the outboard motor and controls and doing all of the electrical work I had no experience whatsoever. Considered hiring someone...but very glad that I did not. Everything has worked perfectly, I learned a lot, and know the minute details of how it all works. I'm 62 but enjoy learning new things every day.
I have even thought about taking some training courses for outboard motor repair.
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I admire the fortitude Bob, the only thing I attend to on the verandas is oil changes. But the same learning curve a guy like Eben has with an honest effort at trimwork is what you would be assuming with outboard repair. Your time is better spent fishing,which is outstanding right now.🔨
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Ya know...I thought Eben did very well taking on that project himself.
I've always had to do for myself, goes back to when I had nothing, and no help from anyone.