Convert Nissan 4 stroke 5hp to 4hp?

[snohomish]

Hi all,
Very informative forum here. Thanks!

I have a 1998 Nissan 4 stroke 5hp NSF 5A. The outboard quits at low idle. I pulled the fuel line into the carburator and got some sediment back with what gas was in there. My plan is to order a carb rebuild kit and clean...hopefully that's it.

I have also read that the 4,5,6hp Nissan is the same, except for the carburator that is in it.
I have had issue with this outboard and its low-end idle speed on my 12ft fiberglass boat. Instead of buying a carb rebuild kit for $50-60, I am considering just buying a new 4hp carburator to improve my low-end idle speed.

Question...
Would doing the above have any significant improvement to my low end idle speed?


What if I changed my prop from a pitch 8 to 7?

Thanks

 

[Sea Rider]

Re: Convert Nissan 4 stroke 5hp to 4hp?

Welcome to the forums,

Seems you shave a clogged carb at low circuit, will need to have it soaked in proper cleaning solvent for some hours. Being a 14 year oldie, better buy a new carb kit, maybe will need fuel/air/idle rpm screw adjustments.

You can convert your current restricted 4 HP into a 5 or 6 HP, will need to buy a new carb that matches specified model number, all 3 are 123 CC. Props have nothing to do with carb malfunctions.

Happy Boating

 

[snohomish]

Re: Convert Nissan 4 stroke 5hp to 4hp?

Thanks Searider.

I will soak carb in cleaner.
Actually I have a 5hp and am considering to convert to 4hp to slow my idle speed. Will my idle rpm decrease, thus reduce the speed of my 12ft boat for fishing? Or would it only make the boat go slower at WOT?

Thanks

 

[Sea Rider]

Re: Convert Nissan 4 stroke 5hp to 4hp?

Both 4 and 5 HP models have minimum idle speed settings which cannot be decreased too much or the engine will stall. On TLDI electronic models you have 3 ideal throlling slow rpm to choose from.

Happy Boating

 

[pvanv]

Re: Convert Nissan 4 stroke 5hp to 4hp?

Idle speed on all the 4/5/6 4-strokes is the same. Idle circuits are the same as well. Only difference is in carb throat size, which affects WOT operation. If you want better low-end control, consider the SailPro "mouse ear" prop, which is low pitch, with large blades, intended for heavy loads, such as sailboats, at slow speeds.

 

[snohomish]

Re: Convert Nissan 4 stroke 5hp to 4hp?

Could I use Sea Foam as my carb dip? Reason I ask is that I can get the Sea Foam in 16oz bottles as opposed to one gal cans.

Thanks

 

[pvanv]

Re: Convert Nissan 4 stroke 5hp to 4hp?

Nope, seafoam is basically a kerosene-type solvent, possibly with some detergents. OK as a fuel additive. Not nearly aggressive enough. You need most of that gallon to completely submerge the carb.

 

[snohomish]

Re: Convert Nissan 4 stroke 5hp to 4hp?

Thanks to all...especially Paul!

I had idle speed issues with my 5hp outboard. I basically took the carb apart and soaked the components for 4 hrs in NAPA brand carb cleaner, changed engine oil and lower unit oil. The outboard idles perfectly now!

Thanks again