8hp nissian trolling problem

[renoduckman]

My dad has 2010 Nissan 8hp that he uses as a kicker. The engine runs fine and idles good. But when you make the slightest throttle movement to speed up the engine seems to surge and rev up. In other words you cant make a small speed adjustment, it rpm seems to jump up. A bit frustrating since you bought the engine just for trolling. Any one have any experience with this engine? Is this just the way it is, or is there some problem with my dads engine? Do you think those flat propellers they sell for trolling might help? The engine is used at about 2000ft elevation, if that means much? Thanks

 

[pvanv]

Re: 8hp nissian trolling problem

The NSF8 and 9.8 have superb throttle control. You should be able to idle down to under 1000 in gear, and should have a gradual RPM increase up to about 6000 at WOT (if you are propped correctly). It's pretty linear, so that half throttle should produce about 3500 RPM, (give or take about 500, depending on the boat and prop). If the RPM "jumps" from idle to, say, 3000 rpm, you may want to get the motor to your local dealer.

Depending on the boat (especially if it is very light), you may find that the NSF8 has brisk acceleration, due to good low-end torque. That might be too much thrust for trolling in a light boat, especially if propped too "steep". If you have the out-of-the-box 3B2B645140 7-pitch 3-blade prop, reducing pitch will give you more low-speed control. Switching to a 3B2W645125 5-pitch 3-blade prop would give you less speed, and finer control of speed. Just don't exceed about 6000 RPM at WOT. The 3B2W645110 5-pitch 4-blade "high thrust" prop (used on sailboats, etc.) would also work, but since it is intended for heavy boats, it will produce a strong "hole shot" coming off idle.

If the motor is just plain too large for trolling the boat, then you can either swap down to a 4/5/6 hp motor, or have a crafty mechanic install a restrictor between the carb and intake (like they do in NASCAR).