# 20HP Nissan 4 Stroke - "studders" at WOT



## Brett (Jul 16, 2008)

What is your top rpm per tachometer?
Air bubbles causing prop to burp?
Rev limiter kicking in?
Spark plug misfiring?

http://www.nissanoutboard.com/Nissan-20-hp-outboard-NSF20C1.html


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## gnuraider (Nov 4, 2008)

Thanks Brett - that is "almost" my motor...except I have the power tilt version with remote throttle configuration.

As far as I know there are no bubbles...there have been no changes that would effect that since last outing.

I don't have a tach, so I have really no idea what my RPM's are, so can't rule out the rev limiter being an issue.

Spark plug misfire...would that misfire all the time, or just under WOT conditions? I am running like a charm even just a hair below WOT.


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## Brett (Jul 16, 2008)

I've had plugs that worked great at lower rpms
but misfired at full throttle. Easy fix, new plugs.


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## noeettica (Sep 23, 2007)

After Plugs go Up 1 Pitch on Prop 

What Prop are you running Now  ?

Part Number You Want is 

3BAB645240

9.25 X 11.5 

10 Pitch not enough 

Motor is Running better ... Boat is slipprier less wind ...gotta be somthing ...

Dave


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## gnuraider (Nov 4, 2008)

Thanks - I will try the plugs and go from there. Been using a stock prop since I bought the boat and never had any issues until now.

Just out of curiosity, how often do you all change your plugs?

Thanks,
Dave


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## Brett (Jul 16, 2008)

> Q: How often should I replace my spark plugs?
> 
> A: Unfortunately,there is no single answer to this question. As spark plugs grow older, they lose their sharp edges as material from the center and ground electrodes is slowly eroded away. As the gap between these two points grows, the voltage required to bridge the gap increases proportionately. Even the best ignition systems will be strained to supply enough voltage to completely burn the fuel. It is at this point, when fuel is being left unburned, that the time has come to change spark plugs.



Whenever the engine starts to misfire...


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