25hp Nissan

[tinman22]

I have a 2001 model 25hp Nissan tiller outboard. I recently had the carb cleaned by a local mechanic and took it out for a test run today. It seemed to really hesitate (kind of sluggish) when initially giving it gas. Then when getting up to speed it never seemed to reach top end and kind of waivered so to speak. I found that by pulling the choke out about 1/4 to 1/2 an inch it ran a lot better on the top end.

What could be the problem...again, the carb has just been cleaned (soaked) by a local mechanic. Thanks for your help!

 

[pvanv]

Re: 25hp Nissan

You didn't mention your model (year is unimportant for servicing but model/serial is everything). You probably have an NS25C3 2-stroke, since you didn't mention 3 carbs, which the NSF25A 4-stroke would have. It sounds like making the mixture richer (by adding choke) improves the running. If that's the case, you need more fuel. Since the carb was just done, there is a possibility that it wasn't done 100% correctly. For example, if the float is too low, the mix would be too lean, and you would notice that quite a bit at WOT. Likewise, you could have a weak fuel pump, or a slight air leak in the fuel line. Any of those things could reduce fuel delivery.

 

[tinman22]

Re: 25hp Nissan

Yes, it is a NS25C3. The motor ran better before I took it to get the carb worked on. Im guessing that the float may be too low and I might have a lean mixture. How can I tell if this is the case (where on the motor)? Also, could I just adjust the lean/rich srcew...if so, which screw on the carb is it?

 

[pvanv]

Re: 25hp Nissan

"Im guessing that the float may be too low"

Don't guess. A proper and thorough diagnosis will save time and effort. Yes, the float could be mis-adjusted, but a number of other problems could be causing your situation as well. If you want to work on the motor yourself, the first thing to do is get a copy of the Factory service manual, available from any dealer, including me. Covers all 1 & 2 cylinder 2-stroke models. Part # 003-21035-1 $44.17. It has the correct procedures and settings that you need, and is the manual that we use in our shop. Working without one would be driving blind.

No, you cannot merely adjust the pilot screw, as it is only there for low speed mixture adjustment. In short, the float level is set correctly when the float is parallel to the carb casting when the carb is held inverted (so gravity pushes the float against the needle). In order to check that adjustment, you need to have the carb in hand, and the bowl removed.

 

[Sea Rider]

Re: 25hp Nissan

Check screw that locks float pin is well seated to carb. Will need to replace float valve if tip is severly worn or float itself is mis adjusted.. If both parts still in good working condition, check pump diaphragrams for wear, change for new. Check both plugs are tight gapped to 1.0 mm and are compatible with your engine.

If correct, try a new gas hose, probably as stated by Paul could have an air leak on tank or engine fuel connectors. Had the same symptons at 3/4 to wot with an 18 which drove me nuts for a long time to find all related problem was due to the hose connector.

Happy Boating