YAMAHA 1998 15HP Two Stroke oil ratio question

[KenLodato]

Hello Everyone and happy new year!!

I picked up a Yamaha yesterday and took it out on the water but it started to stall out, I realized the gas tank i was using had a oil gas ratio of 50:1, my 15hp takes 100:1. Do you think since i was using the 50:1 it would force the motor to stall out? Thanks for any advice!

Ken

 

[Silvertip]

Re: YAMAHA 1998 15HP Two Stroke oil ratio question

No.

 

[extreme01]

Re: YAMAHA 1998 15HP Two Stroke oil ratio question

no it would just smoke a little more

 

[KenLodato]

Re: YAMAHA 1998 15HP Two Stroke oil ratio question

Well i made my gas tank 100:1 and now its running smooth ever since the 50:1, no stalls and starts up instant after shutting it off. Before with the 50:1 it would start, run for a few minutes then stall out and would be a pain in the *** to start right up afterward, I would have to play with the choke before it starting up.

PS: I ran it for an hour and half straight.

 

[tazrig]

Re: YAMAHA 1998 15HP Two Stroke oil ratio question

Are you sure it was 50:1 to start with? Possibly really old gas? I've winterized plenty of Yamaha motors using 50:1 and they run fine, just a little smokey.

 

[KenLodato]

Re: YAMAHA 1998 15HP Two Stroke oil ratio question

Yes it was 50:1, I used it for my two mariners a few days prior. I went out fishing today, everything seemed fine, went 6 miles out to the ft lauderdale inlet and it gradually slowed down while i was in full throttle, until it completely stalled. So i played with the choke and got it started up, and it's only about 20% of what it was previously going in full throttle.

I have a video, I will have uploaded by tonight, it slows down in full throttle from 20% of the normal speed to 5%, getting even slower so i lay off the throttle then back on and so on. The compression is 120/120 in the cylinders, peeing normal, motor isn't hot and the throttle isn't the issue, as i checked it manually to test if it was stuck or broken, in which it wasn't. Also i found out its not a 1998, its a 1993. I appreciate any feedback or solutions, thanks all.

Ken

 

[99yam40]

Re: YAMAHA 1998 15HP Two Stroke oil ratio question

Compression, spark, timing, and fuel/air ratio are the things that effect motor firing properly , one of them is causing the problem.

Test what you can when problem is there

 

[KenLodato]

Re: YAMAHA 1998 15HP Two Stroke oil ratio question


I just looked at the motor now and the spark plugs seem to be getting hot and melting the wire attached to them and im noticing oil coming out of the top one.

 

[kfa4303]

Re: YAMAHA 1998 15HP Two Stroke oil ratio question

Ah ha! That may be your problem. Hopefully, it something simple. Perhaps, the spark plugs are not be torqued down to the proper spec and/or the threads may be stripped allowing fuel/oil mix out. Either way, you'll need to fix it. I would start by double checking the correct brand/model of the plugs you need and investing in a new pair for good measure. You can then reinstall them and tighten them down to the torque value shown on the head. If that doesn't do it, the threads in the head are probably stripped/damaged, in which case you'll need to have them re-tapped, or use something like a helicoil to repair them. The worse case scenario is that you would have to get a new head. Btw, I'm up the road a bit in Tallahassee.

 

[KenLodato]

Re: YAMAHA 1998 15HP Two Stroke oil ratio question

I bought the new spark plugs today, i am going to get some gas and oil tomorrow and do some testing. How do i ensure i am tightening them in to the torque value correctly?? Thanks for your help.

 

[KenLodato]

Re: YAMAHA 1998 15HP Two Stroke oil ratio question

Video of my yamaha slowing down then having to go up and down with throttle, sorry there is no audio, i got water in my phone that day. [video]http://www.leadest.com/yamaha.mp4[/video]