F90 with too much oil

[Broken1]

I have a Yamaha F90 less than a year old with under 40 hours on it. I've changed the oil once as outlined by the break-in procedure. Went back with the YamaLube 10W-30. The last two times out I noticed smoke (excessive) on start-up. I checked the oil level and found it is WAY too high. No milky sludge and really didn't notice gas smell but since the oil was so clean still i can only assume it is from gas. I KNOW I didn't over fill when changing as I checked it several times after doing so over a couple of days prior to running it. I use the ring-free and the fuel conditioner as recommended by Yamaha. There are no other problems evident and it still runs as good and quite as ever. Obviously I need an oil change but I'd like to correct the problem so I won't have to continue changing the oil, especially at what it cost. Any advice or recommendations as to what I should check that might cause this problem would be greatly appreciated. Many thanks!

 

[BaileysBoat]

Re: F90 with too much oil

Common complaint with all 4 strokes. Don't get enough heat to burn off fuel dilution into crancase. A lot of trolling without a high speed run makes it worse. Make sure you are reaching max rpm and not over propped. I had the same issue with my F150 until I went down in pitch. When you change the oil don't fill to the full line but 1/2 way up the dipstick.

 

[Broken1]

Re: F90 with too much oil

I'm running the factory prop and can reach the 5000 RPM range at WOT. I don't make many long runs but when I do, I don't exceed 4000 RPM. Just don't like running the engine that hard. If I run WOT some this weekend, would that burn off the excess fuel in the crankcase or should I go ahead and change it?

 

[BaileysBoat]

Re: F90 with too much oil

You need to be at the high end of the rpm range, 6000 rpm at WOT.
I would change the oil, then get the correct prop.

 

[Eagle180]

Re: F90 with too much oil

As BaileysBoat outlined, this is a common complaint with 4 strokes. You can google "yamaha making oil" and get loads of hits for your reading pleasure. I have a Yamaha F115 with the same problem. It is not as bad now that:

1.) Bad (leaking) mechanical Fuel pump was changed
2.) Hotter thermostat was installed
3.) I run it WOT - 5700-5900 RPMs at the end of my boating day for 5 or 10 minutes if possible... or longer.

The oil level does rise on the dipstick a bit, especially if I troll a lot, but not as bad as before the above changes.

I called and spoke to Yahama directly and the person I spoke with said - "if you run low RPMs (3000 or less), you don't get the engine hot enough to burn 100% of fuel and you are going to get blow-by". He told me that I should run at WOT at the end of each trip. I know... in my opinion.. you shouldn't have to do this, but this is what he told me.

Also, I have talked with 2 mechanics at two separate boat dealers in my area about this issue and they both tell me that it is their experience that people 'baby' these outboards way too much.. they told me these outboards were designed to be run 'hard'! I am just repeating what they told me!

I have read loads of posts/threads from people with the same problem and also with people who don't have this problem. You should keep a close eye on it as I do.

Good luck...

 

[rodbolt]

Re: F90 with too much oil

your over propped
no such thing as a factory prop from yamaha.
thats the riggers selection.
they got it wrong.
need to prop it so it can turn at least 5800 RPM with that days load.
need to run it a few minutes above 4500 coming home if possible.
however there could be another issue or two.
but first get the correct prop on it.
on the smoke, do you store the motor trimmed up or down?

 

[Broken1]

Re: F90 with too much oil

I'll check the prop specs. I store the engine trimmed down mostly due to limited space in the garage.

 

[rodbolt]

Re: F90 with too much oil

thats most likly the smoke issue, need to trim it up for 15 to 20 min at least once its done running.
some oil can leak past the rings when trimmed or left trimmed down after running.
a puff of smoke and it goeas away. your owners manual probably makes mention of this and there is a tech bulliten about it.
no research needed on your prop, its simply to big or your not using the trim.
either way the engine is lugging and will make oil.
when that F90 left japan in the crate there was NO prop on it.
the rigger selects the prop and most likly makes minimum wage.

 

[Broken1]

Re: F90 with too much oil

Got it. When I take the boat out of the water the engine is trimmed up and remains this way for at least an hour before being parked in the garage. The current prop is a 13x19 and the boat is an 18' modified jon. Based on the excellent and much appreciated responses, I'm going to change the oil and run WOT this weekend. When doing so I'll also check to see what the RPM's top out at. I honestly can't remember since it's been so long in reaching WOT.
Thanks to all for the replies!

 

[mommicked]

Re: F90 with too much oil

Broken1,Glad to finally meet someone who has a similar boat/motor.I have a 03 G3 1860sc jonboat,03 F90 w carbs.I got it in 07.It came w a yama 13 1/4x 17 alum.3bld prop.I rarely ran @ wot because motor didnt seem to run that smooth there.I suspect the prop was cavitating?or blowing out?It performed better @ 3/4 throttle,not alot slower than wot.I have since gone to a 4blade alum solas 17pitch and the boat/motor perform alot better.now wot is smooth and steady, control in turns is unreal compared to the old prop.top speed seems faster too.(to be verified soon)however I do not have a tach yet,comming soon also. Im eager to find out my rpms as Ive found my engine is also makin oil.Ive only run new prop twice. less than an hour,spanked the crap out of it! and its time for an oil change anyway.I have done a fair amount of trolling @ idle watchin the fishfinder and a little faster w the old prop, lugging the engine before I found out about making oil.so I dont know when It "made the oil"then or now.maybe both.please post your RPMs when you can.Ill post my speed/RPMs soon.Ive removed and checked my fuelpump pumping the ball and waiting.did not see any leakage there.thanks Randy

 

[Broken1]

Re: F90 with too much oil

WOT with full tank of gas fishing gear and one person is 5700. Wasn't able to check GPS speed due to storming and rough water. 2010 G3 1860 CC DLX.

 

[mommicked]

Re: F90 with too much oil

Thanks for the update,and everyones advice.I wonder if the engine is lugging at 4000 w the 19 or any pitch?.I may go down to a 15 or less once I get the tach.as these boats dont like chop,beats the hell out of it,and the only option is to slow down-LUG the engine.I guess from experts advice that a low pitch would help w not makin oil when trying to run slower because of conditions right? higher rpms at a lower boat speed.I also understand that lower pitch is needed for heavy loads and Im sure overproped/overloaded =lugging alot= Makin lots of oil quick!!I think jonboats w ribbed bottoms and shallow Vs are alot less hydrodynamic than smooth fiberglass hulls w lifting pads etc.and that contributes to the lugging/oil making.but Im no expert.