GAS in the OIL??????? (4 Stroke Yamahas)

[Pas Bon]

I work for a state agency in LA and we have several Yamaha 4 strokes.
115's and 200's. We are having a chronic problem with GAS in the OIL in all models. We have a repair guy that is changing the thermostats and running ring seal and using synthetic oils to fix and or avoid this problem. What do you guys know about this?

Thanks
P

 

[zzzzz]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

we were advised not to use synthetic oil in 4 strokes as they don't handle the moisture from crankcase condensation as well as mineral based oil but there are many schools of thought on this...go to www.bobistheoilguy.com for more info...Yamaha's dealer website also has info about gas in the oil... a lot has to do with the way the motors are operated or stored-extensive periods of idling,etc.

 

[ricwing]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

There is a good write up about that problem in, frequently asked questions

 

[DJ]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

Yes, go to FAQ's.

Any engine running that cold is going to have combustion gases and condensation (water) in the crankcase. Bad? Who knows. The jury is still out on that one.

Inboards and I/O's have dealt with this issue for years. However, those engines were heavy cast iron blocks that could take it.

As said, the jury is still out on this issue.

The only advice I have is to step up and change your lube oil more frequently. The oil of choice is up to you. I like OEM stuff. I've never been let down with OEM parts and accesories.

 

[rodbolt]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

first big thing is to insure the engine can spin to 6000 RPM with the CURRENT load.
next is to run a leakdown test, doesnt happen often but occasionally the ring gaps will line up.
next is after any extensive idle time the engines need to run above 4K for at least 30 minutes.
also make sure all the linkage is adjusted properly.
EFI is very very sensitive to overpropping.

 

[Yamauser]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

At the end of the season, I discovered my F115 was making oil. I have seen it written that all four-stroke engines have this problem, just some of the owners have not discovered it yet. This can't be true. There must be plenty of four-stroke owners who have not experienced this problem. If so maybe you could share some of your secrets.

 

[zzzzz]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

on the F115 Yamaha told us when changing oil-drain the crankcase,put the drain plug back in and tilt the motor up for a few minutes,then trim it back to vertical and drain any leftover oil from the crankcase...reason being that there are some oil passages in the motor that slope downwards and retain oil when the motor is vertical and if you put in the stated amount of oil it results in being overfull

 

[Woodnaut]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

I had this problem (making oil) with my F90 earlier this year. The cause turned out to be I had the engine over-propped. This is to say, I was only getting about 5,200 RPM at WOT. I repropped and brought it up to 5,900 RPM and the problem resolved itself. Based on my experience, Rodbolt's advice to check your RPM at wide open throttle is a good (and inexpensive) first step. - Woodnaut

 

[Yamauser]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

Great tip Z. I never did that when I changed oil. It might not be making quite as much oil as I thought. Woodnaut, My F115 is also over-proped by about 700 rpm. I will down size the pitch from a 19 to a 17 in the spring. It is hard to believe that a little over-prop could cause a major problem. But, from what I have read, it is one of the major causes of making oil.

 

[jerkin]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

If you're looking at 700 rpms you will probably have to go to a 15 pitch to get up to the correct range.

 

[rodbolt]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

modern EFI is very susceptible to over propping due to the fact it does not rely on engine vacum to move fuel from the rail to the intake. when over propped combustion pressures spike and leaves quite a bit of unburned fuel that will be pushed past the rings.
its imperative that engine can turn 5800 + with the CURRENT load.
had an F150 not long ago in with 3 detonated pistons at 15 hours.
was propped empty,after adding 6 bench seats and 14 people it was rather overpropped. yamaha covered it for some reason.

 

[Yamauser]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

This is my first 4-stroke and first Yamaha. From what Robot and others have said, it sounds like the way I have run the motor completely wrong. I thought I was babying the motor by running at the lowest rpms that still maintain plane. I thought the lower rpms would extend the engine life.
It also sounds like trolling speed is a real killer. That is a tough one since one of my favorite spots has miles of No Wake zones.

 

[rodbolt]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

4 strokes like to run.
only reason I dont push my F150 is cause I am cheap.
3600 is about 30 mph at 6.2 GPH, 4800 is about 38 MPH at about 11.2GPH.
I aint in that big of a hurry.
but yes I do run it the last 30 min or so above 4500.

 

[Yamauser]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

Can someone refresh my memory? Is it one inch of pitch equals aobut 200 rpm? If so, in my case, I should be looking at a 15p prop.

 

[srw1979]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

So...I have an F115 that is getting fuel in the oil as well. I heard some of you all mention that your boats were over propped and this was causing the fuel to get in to the oil. A mechanic told me my boat was under propped, could this cause fuel to get in the oil as well? Also, I'm new to the terminology so just to clarify I guess I should be running between 5100 and 5600 RPM's at WOT but I'm hitting up around 6200 RPM's and tripping the "rv limiter". Any of this sound correct to you guys? Thanks!

 

[Yamauser]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

srw: I am not an expert by any means, but some of the guys on this forum are and they could answer your question about under propping. Like you, I am trying to muddle though this problem. So, I was wondering how you figured you should be running beteen 5100 and 5600 rpms at wot? I can find nothing so precise. My manual states between 5000 and 6000, that's a broad margin.

 

[rodbolt]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

5000 to 6000
yep
however if you keep reading there is a reccomendation to prop it to the high end for the load being carried that day to insure maximum performance and engine life.
its there just keep reading

 

[Yamauser]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

Got it Rodbolt. I still don't know why they just didn't say the range was 5,500 to 6,000. So, since I hit 5,400 with a 19p, I should hit about 5,800 with a 15p. Please let me know if I am wrong, I'll start shopping for a 15p.
Bill

 

[ghind]

Re: GAS in the OIL??????? (4 Stroke Yamahas)

You should only need to drop 2" in pitch to pick up the extra 400rpm if you are aiming for 5800. That said, these motors make horsepower at the very high end of their RPM range and maybe you would be better off at 6000 WOT. Evinrude publish dyno graphs for the F150 you will find it in their E-TEC comparisons in their web site.

Also, prop it with your normal load. No point hopping in the boat by yourself for your WOT prop test runs and then running a heavier load for day to day running.