yamaha 250 cutting out

[thefishingfreak]

hello ,i just bought a 1990 grady white 28 marlin<br />w/ twin yamaha 250 v76 the port engine cuts out at high rpm. about every two to four seconds and then is fine , the tach shows a drop of about 200 rpm.its like a cylinder is not firing all the time .all the plugs look good and it seems to be getting worse the more i use the boat(wasn't happening at all when i first got it)i work on cars for a living and have had three boats before this one but this is my first outboard, any help would be appriciated

 

[rbu]

Re: yamaha 250 cutting out

I'm not that familar with the new Yam's, but I hear there were issues with the Oxygen sensor. This is a newer SWSII motor right with the OX66 injection? There is a post on another website from a guy with a 250 Yam with similar problems, he gets to around 4200 and then the rpm's surge 200-300. Everyone is leaning towards the O2 sensor. There might have been a recall to upgrade the sensor.

 

[thefishingfreak]

Re: yamaha 250 cutting out

thanks for the reply. this is an original 1990 250 i dont even think it a saltwater series 1 its carburated and oil injected and its not realy surging its lagging compared to the other engine

 

[rbu]

Re: yamaha 250 cutting out

My apologies, I didn't realize that the older 250's were V76.<br /><br />Well, in that case, I would go through the fuel system first. Check the obvious, if you haven't already. Fuel filters, connections, etc. Drop your carb bowls and look through the carbs. The older Yamahas had issues with the fuel pumps, there are small screws in there that will start to rust. If they are original, then it's probably a good idea to replace them.<br /><br />From what I know, the electrical systems on Yamahas are pretty sound, even the older ones. That's why I would start with the fuel. Oh yeah, double check your compression.<br /><br />Good luck.

 

[uduck]

Re: yamaha 250 cutting out

Hello, I'm having a similar problem with a Yamaha 200, carbs plus oil injection Saltwater series. On the first outing this year is began to cut out, loose power then restore power. I changed the water separator filter and this seemed to help, but I can get only 4100 rpms with the motor trying to surge up to 5000 at times. <br />My plan is to replace the fuel and add some Sea Foam to fresh fuel. I have used the Yamaha Ring Free for two years and have a heavy hand with additives; possilby the fuel is too "additive rich". I'm not mechanically inclined and am hoping for a solution in a can. Any ideas?<br />Thanks

 

[thefishingfreak]

Re: yamaha 250 cutting out

i changed the fuel filter the water separating filter and all the plugs with no change at all .i have ordered the three fuel pumps from the dealer about 30 bucks a piece and i will let you know if they work{maybe in a week or so}

 

[pthein]

Re: yamaha 250 cutting out

Make sure the primer bulb is not leaking air or fuel. Also I think there is a fitting where the fuel line connects to the motor. Change both the sides (hose and motor) - these are notorious for leaking.

 

[thefishingfreak]

Re: yamaha 250 cutting out

well the three fuel pumps have solved the problem, the boat is running great so far...

 

[ruel42]

Re: yamaha 250 cutting out

I had a similar problem with a Johnson 225. It turned out to be one of the coils had a bad connection and that was causing it to rev up and down like you described. I found this out by running at full speed and when the motor dropped speed I shut it of immediately and did a spark plug check. What this reveled was one plug was very wet and the others had a clean burn. Then to confirm the spark I placed a spark tester on that cylinder and watched it for a weak spark. And that was the problem. The tough thing about this was when I replaced the coil it was still doing this. It turned out to be a bad wire leading to the coil from the power pack that was causing the problem. <br />I hope his helps you with your problem. Also, on a side note I had a Mercury 200 one time do the same thing and it turned out to be a loose jet in the carb. What would happen is the vibration would let it tighten and loosen letting loose RPM.<br /><br />Good luck finding your problem!!!<br />