2007 Nissan 15HP Rough Idle

Hello All. I bought this motor new in 2008. I put approx 100 hrs on the motor from Aug until Oct. Last time I had the boat out the engine would not idle and kept stalling when I was trying to dock it. Anything over Idle and it would run fine. I changed the plugs and tried it again with the same problem. The fuel filter is fine. Does anyone know if this is a common problem? Is it possible the carb could be plugged in such a short period of time? I am very mechanical and could probably take the carb off and check for a plugged jet but prefer not too unless I absolutely have to. Any thoughts or suggestions would be great.

Thank You,

Brian

Re: 2007 Nissan 15HP Rough Idle

If your outboard was stored over winter then it is probably the carb.
You need to add a fuel stabilizer if you let it sit for longer then a couple months or so.
Your best results will be if you soak the carb in a cleaner for a day. Run a bread tie (minus the cover) through any orifice and then douche the carb with carburetor cleaner and then blow it out with compressed air.

Re: 2007 Nissan 15HP Rough Idle

thank you whoopbass. I didnt make myself clear but the issue started last fall. The motor never sat more than a week at a time prior to the problem. Also I did change the spark plugs to no avail. The engine was never run prior to last August. I literally put 1000 miles on motor btwn Aug and Oct. At the end of the season last year I ran the gas out of the carbs. I have not tried running the motor yet this year.

Re: 2007 Nissan 15HP Rough Idle

If the idle speed is OK, then you need to do some troubleshooting. Did this problem start last fall, or is it this spring? Sometimes just adjusting the idle stop on the 15's is all you need.

Re: 2007 Nissan 15HP Rough Idle

Thanks for your reply Paul. The Engine was idleing fine last October when I was on the lake. When I slowed down to pull in the launch area the engine would not idle at all. However it does run fine if I start it in neutral with some throttle applied. it just refuses to idle at low rpm. I checked the throttle stop and it is fine.

Thanks again

Re: 2007 Nissan 15HP Rough Idle

Have the carb cleaned.

Re: 2007 Nissan 15HP Rough Idle

TOHATSU GURU said:

Have the carb cleaned.

Click to expand...

Yep. That sounds like it.

Re: 2007 Nissan 15HP Rough Idle

Brian594 said:

Thanks for your reply Paul. The Engine was idleing fine last October when I was on the lake. When I slowed down to pull in the launch area the engine would not idle at all. However it does run fine if I start it in neutral with some throttle applied. it just refuses to idle at low rpm. I checked the throttle stop and it is fine.

Thanks again

Click to expand...

If carb is clean, firts check idle rpm, must be slight 800 in gear, 950 in neutral, will need a tacho for adjustment. If still with problems, check also air/gas idle adjustment screw.

Happy Boating

Re: 2007 Nissan 15HP Rough Idle

Thanks everyone. I been away for awhile. Since my last post I have removed the carb. The Idle jet and the main Jet were both clean. Also the whole inside the carb body connecting both was clean. As a precaution I cleaned all jets anyway and reassembled. I didnt realize the carb has an air/fuel mixture screw. I dont recall seeing it in my service manual.

Thanks again,

Brian

Re: 2007 Nissan 15HP Rough Idle

It doesn't have an air mixture screw...Just an idle adjustment screw. Clean the carb, by soaking it, as the internal passages can be pluigged where you cannot see it.

Re: 2007 Nissan 15HP Rough Idle

Huuummmm... I had the same problem with my 2008 Tohatsu. It would not idle right out of the box. I struggled with it for two months, and believe me, trying to dock a boat with a fast running engine was no fun. The only way I could get it to ilde down was to play with the choke, not a good thing to do, but desperate times call for desperate measures. I was camping deep in the High Sierras at about 6,500 feet and the nearest dealer was a hard six hour drive away. I thought the idle problem might be do to the high altitude. When I got home I took it to a dealer, he took the carb apart and it was clean, stable did its job. He drilled out the plug that covers the secret screw, ya know the one Tahatsu dosen't show in the manual. A few turns of the screw and the problem was solved. Well at least at sea level, we shall see how well it works up in the mountains.

Re: 2007 Nissan 15HP Rough Idle

These are two different problems. One was correct out of the box, the other was not. The one that was right at first likely has some gunk in the idle circuit.