OX66 Premixing

[Tucker]

RE: 1999 150HP OX66
Gents,
Getting ready to disconnect oil injection and go premix. To those with OX66 motors that have done this; has the O2 sensor failed prematurely because of carbon foul? Planning on doing the ring free thing every other tank full. Not worried about plugs, they're an easy change.

[jf123]

Sure. With the oil pump the mixture varies. If you premix you will either be over oiling or under oiling which neither one is good. The oil systems are very reliable. Why would you remove it?

[bigfish1229]

you will not notice any performance difference in pre mixing and my o2 sensor has been fine for about 2 yrs now on a premix 225 vmax. i have severl ox66 motors some pre mix and some not and notice no difference between them

[Tucker]

Well, well. Assuming, with a name like Bigfish, you spend some time *****ing. And if you haven't messed up the 02 sensor in 2-yrs well I should be in good shape.

Gents, I'm not a neanderthall by any stretch, but I've read back to about page 100 and you can't find a page of posts without someone having a problem with something related to the oil injection. So when all the pros say the Yamaha system is very reliable, sorry but I have to disagree. Well, if you don't mind doing all the maintenance and don't mind worrying about 2-oil pumps, 2-float sensors, the filters, the check valves, correct linkage settings, etc I guess oil injection is the right thing. With premix, lets see...dump 1-gal oil, add 50-gal of gas, done.



There also seems to be an inherent problem with oil injection, my type at least. If you punch a hole shot after *****ing the VST tank is full of gas at 100:1 so...you're running at full throttle at 100:1 until the oil pump catches up. Is my thinking flawed on this?

[jb123]

id bet yamaha is hiring in their engineering dept....

[jf123]

I can't imagine the engineering at yamaha would design a flawed system. If so they likely would not be in existance today. Remeber also that you are only reading about problems on this site there are quite a few engines running in this world that don't have issues.

[Tucker]

They should be. It's human nature, if something is a PIA to maintain it won't get done. And jb, I believe you've replied to many of those posts. I'm not an engineer but all we're trying to do is mix oil with gas. You'd think they would come up with something less complicated. I've read the maintenance procedures on here. Remove the oil tank, drain, clean, remove and clean the oil filters, etc. Yea, right. It's the geezer in me coming out. I like things simple.

I would be interesting to know the number of people with oil injected motors 3-years and older that have not had a problem with the system.

[jb123]

they pair i have now are 9 yrs old, wouldnt dream of removing that system and havent had 1 issue with it....... but to each their own.

[Tucker]

What motors do you have jb?

[jb123]

2000 200ox66's

ive owned yamahas for the last 16 years , 9 different motors and only had 1 issue, an oil control unit on an 89 pro-v.

[bigfish1229]

my boats get the ever living piss ran out of them every day. from 200 mile offshore trips in my 27 grady white to tournament fishing in my lake and bay. i own these motor for one reason, and one reason only. i can trust them. yes from time to time they have hiccups but every engine does. i have had 5 powerhead failures while running ox66 motors in 9 years with 4 motors thats not bad. all were oil injection related. is it a good system absolutely. is it good for the way i run my boats and the amount of hours i put on them, not as far as i can tell. i get about 1300 hours out of an oil injected motor, and about 3000 or more out of a premix motor. like jb said to each his own but i know that is costs me about $3500 in paarts to build an ox66 properly so if i can double the life of mine by mixing it. by all means thats what ill do. and to answer your question yes i do some significant *****ing time in the winter months

[BQUICK]

I've got 1989 200s with never a single problem with the oil injection. Never even changed the oil tank filter......probably should though....

[robert graham]

my motor's a 1999 Yamaha 90C premix and I bought it new and the simplicity and dependability of the premix is hard to fault. 10+ years running with no problems at all, even running the original plugs(I do sand-blast them). I've had a Yamaha 115HP with the oil injection and never any problems with it either. but give me a choice and I'd pick the premix anytime. only problem, I don't think Yamaha makes any mid-range motors without auto-lube, so guess if I have to buy a new motor, it'll have the oil pump on it. thoughts from a neanderthal/caveman.....

[robert graham]

I've run my 1999 Yamaha 90C premix 10+ years with no problems at all and I like the simplicity of no oil pumps, tanks, filters, valves,etc....there's just less to go wrong here and i just dump in the oil, Ringfree, Sta-Bil, gasoline and no problems! I've run Yamaha autolube motors with no problems too, but given the choice I'd prefer premix. Of course, i don't think Yamaha makes any premix mid range 2 strokes any more...they come with the oil pump, so if I have to buy a new 2 stroke motor it's probably going to have an oil pump on it. guess most folks go with what works best for them. thoughts from the old caveman/neanderthal...

[Tucker]

I'll say it again, you're gonna be hard pressed to read a page of this forum without someone having problems with the oil injection system. Don't get me wrong, I thing it's a great idea. Keeping the mixture rich in gas through the entire RPM range is the ultimate tuning. I just think it needs to be more fool proof. I'm sure we'll see it evolve as the years pass.

We all know the 2-things that can cause catastrophic failure with these big 2-strokes are overheating and lack of oil. We change the water pump every 2-years whether it needs it or not. Not much we can do with the oil injection other than clean & inspect. If that little Mikuni pump takes a crap we're done. I understand the blunt sound of a 6-cyl seizing at 4500 RPM is something you never forget.