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Nissan 90 roughness

rogerwa

New member
"I just picked up my new to me

"I just picked up my new to me 1989 90 HP Nissan and mounted it to my pontoon boat. Other than the initial problem I had with the idle settings (I think dealer set the idle on muffs not tank), it now idles very well around 900, which I believe is spec, and runs perfect from 1900RPM on up.

My question is that between ~1000RPM and around 1900RPM (I guessing the point at which the butterfly cam is engaged), the motor runs but is very jerky. It doesn't die or lose power, its just that the powerhead is jerky and feels very uncomfortable instead of a smooth increase in power.

The dealer cleaned the carbs before delivery so I am assuming they are clean. Is this the nature of this motor or is there a fine adjustment to make that could help smooth it out.."
 
"Roger, I would get ahold of t

"Roger, I would get ahold of the dealer again and ask "how they cleaned them".

Without removing, disassembling and cleaning you could still have a clog or gummed condition in the low speed jets.

That condition "could" explain the roughness in that particular rpm band..."
 
"Thanks, I will pull them and

"Thanks, I will pull them and ensure these jets are clear.. I will also check with the dealer."
 
"After asking the dealer, I fo

"After asking the dealer, I found they simply ran the thing in a test tank and did not touch the carbs, so there is probably gunk in there. Once I have them off, how do I access the low speed jets? I have not purchased the manual yet as I have only had this thing for 2 weeks. Can I do this without drilling any plugs??"
 
"Roger, no drilling needed, bu

"Roger, no drilling needed, but get a manual before you try this. It's not difficult, but definate proceedure to follow.

A 30 dollar manual, besides being priceless for doing this task is a whole lot cheaper than a 200 dollar plus replacement carb if you screw something up..."
 
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