My neighbor has a 3 year old Yamaha 75 hp 4 stroke outboard that has started to blow smoke!!! its really smokes at start up……..just started doing it…and its just past warranty!!!
I told him to get a compression check done and see what that tells!
Check to oil levels.
I know a few four strokes that make their own oil and when it gets over-full that is when they start to smoke at start up.
I have seen it first hand so change the oil and your good to go in some instances.
I don’t know anything about the Yammi 4’s, but my Suzi 4 stroke will NOT tolerate synthetic oil. It smokes, and “grows” oil. Had a dealer tell me the rings don’t seat right and it’ll push fuel past the rings. I took the synthetic away and went back to a petroleum based oil and it’s fine now. If he’s using synthetic, or even part synthetic, maybe this will help- – – jerr
I run amzoil in my 140 Johnsuzuki and it works great? never a problem with over 225 hrs on it!
I’ve been running Mobil 1 in my F115 for 6 years, haven’t noticed a problem. Just changed oil so next time I’ll try Pet based, should be changing it again 1 more time this year.
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I run amzoil in my 140 Johnsuzuki and it works great? never a problem with over 225 hrs on it!
I tried the Mobile 1 and the guys @Maplewood Marine told me that’s what the problem was. My little DF50 has over 300 hrs on it and I’ve had no problems since I went to the petro based oil- – -different strokes for different folks 
– – -jerr
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Check to oil levels.
I know a few four strokes that make their own oil and when it gets over-full that is when they start to smoke at start up.
I remember reading about this in a repair forum once……the oil level actually goes up…..cannot remember exactly why but it does… 
In Our world that would be valves, or valve guide seals. I think that if oil level is to high it will burn oil all the time and engine rpm will be down a bit check air box for oil deposits from engine breather hose
2ks
My neighbor checked the oil level last night…and it was “over full” so he is going to drain the oil and try it again
I believe it was said….that you need to run the motor awhile hard..to seat the rings?
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I believe it was said….that you need to run the motor awhile hard..to seat the rings?
Just something to check every now and then, mine still makes its own every once and a while 
You won’t be able to tell until it gets cold out, but when the engine is cold, does it idle rough? If you bring up the RPM’s slightly while cold does it sound like its backfiring through the carbs?
Purrrrs like a kitten, 99% of the time.
Even in Oct.
Be very cautious of “growing oil”.
With any motor, when you are gaining oil, you are truly gaining raw fuel, pass the rings and into your oil reservoir. This does contaminate your oil and you really need to drain and change, as well as change your oil filter.
Do what you have to do to seat those rings. That raw fuel mixed with your oil is NOT helping your crank bearings.
I’ve always heard you should never ever use synthetics right out of the box. You need to use petro based oil through the entire break-in period. After that, synthetics are fine.
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I’ve always heard you should never ever use synthetics right out of the box.
Unless it comes from the factory with synthetic, you should break it in first. The only engine I know of with factory Mobil 1 is the GM 502.
I believe your right about the break-in period. I switched to Amzoil after I had the break-in hours on mine….
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