5HP Nissan 4 stroke running rough, why?

[Adirondacker]

I have a 4 stroke 5 hp nissan year 2000.
It starts in the test tank well. Idles fine. When I launched this past summer, when power was put on, she would stall out. She would restart, some times one pull, some times it took several. Choke, no choke, squize primer bulb, elevate fuel tank, do combinations, no real change or pattern. After an hour, I could get it to run at 1/4 throotle, any more, stumble...stumble, if not depoawer imediatly, there would be no recovery from a stall. Ran it for 8 miles on the boat delivery I was doing, frustrating. I never got it to run right.

The oil was over filled from previous owners mechanic. Drained it down, no change. (do you measure the level with the stick screwed in, or just placed in the hole?).

The low oil light only flickers in the final revolution or two, so that is not causing the shutdown. I can't tell if it is rich or lean.

I'm used to OMC's they ussually don't idle due to clogged jets, so this has me baffled.

I feel a carb overhaul is in my future, just wondering why it idles so well, I don't want to tear down a practically new carb if something else is the cause.

Motor has little use, looks spanking new under the hood and outside, I think it spent most of it's life in the garage.

Thanks for any advice,

 

[pvanv]

Re: 5HP Nissan 4 stroke running rough, why?

I'm assuming you have an NSF5A or A2, right? Year is unimportant; model/serial is everything. Your oil may still be over-filled. It requires a surprisingly small amount in the crankcase. You check it with the stick screwed in. D/L a copy of the owner's manual at http://www.nissanmarine.com/tech_talk/owners_manuals.html Middle hash mark on the stick is a good spot. It still may be too lean. That could be restricted fuel delivery to the carb, improper float height setting, or dirty/varnished carb passages. Yes, varnishing usually causes poor idle, but I have seen symptoms such as yours cured by a good bath in real carb dip, followed by a blow-out with generic carb spray, then a careful reassembly. Be sure the carb base gaskets are good, and the mounting bolts tightened evenly and snugly.

 

[Adirondacker]

Re: 5HP Nissan 4 stroke running rough, why?

It is an NSF5a, serial 17226.

On a carb tear down, should I wait until I get a carb kit, and do those come with the gasket that goes from the carb to the block?

 

[pvanv]

Re: 5HP Nissan 4 stroke running rough, why?

You will want a 1-gallon can of real carb dip from the auto parts house, as well as a can of generic carb spray. The soak in the dip will take 4 hours at room temp. May as well wait until you have the kit.

The kit does not come with a base gasket. Sent you a PM with part numbers and pricing.