5HP 4stroke Wonbt idle slow for very long

My motor is about a 2003 model

My motor is about a 2003 model and came with my used sailboat. Runs good at faster speeds. When idling it will only idle slow for maybe 1 to 2 min then quit. I'm thinking it to be a dirty carb problem as when I first bought the boat is was idling real bad until I added some "SEAFOAM" fuel addive. It got much better but still will quit after about 2 min of idle. I suspect carb needs a good cleaning. Sending for a Nissan service manuel. And will probably need a carb kit. What do you think? Need to replace the raw water impeller too.

"Chuck, if the motor is "n

"Chuck, if the motor is "new to you", it wouldn't hurt to "assume" that it's last bit of maintenance was never done or at least maybe been "put off" for a while.

You should change the impeller and lower gear oil. Change the engine oil and the spark plug.

Check/replace the fuel filter (believe there is a small inline filter in the hose leading to the carb).

The carb may need a good cleaning, but your idle issue could simply be related to an old spark plug and the need of an oil change...."

"Graham,

Agree with you 100

"Graham,

Agree with you 100%. Have changed the spark plug,changed the fuel filter, crank case oil changed and lower unit oil changed too. When motor quits I need to squeeze the fuel bulb and pull the choke to start it again. Bought a service Manuel to see the procedures."

"Chuck, the need to squeeze th

"Chuck, the need to squeeze the bulb and choke it may be indicative of a bad fuel pump..."

"Graham,

Hummm good point.

"Graham,

Hummm good point. Since the engine is new to me,and the end of our season I think I'll clean the carb and see. Although it runs very well at fast idle and all other speeds, It is at the slow idle that is the difficulty. Seems when you turn the throttle up it will do nothing--then race to a fast idle. Turn the throttle back slower it is fast to slow run for awhile and the slowly die off and stop."

"Chuck, sure, cleaning the car

"Chuck, sure, cleaning the carb never hurts and then will rule that out as the issue.

I don't have a Nissan/Tohatsu manual, but Tohatsu is building all the small Merc's now - and do have the service manuals. Aside from a couple of subtle differences they are identical.

So if there is something in particular that you are looking for, just drop me an email and I'll send you the section that applies - I have them all on computer..."

"Graham,

That is nice of yo

"Graham,

That is nice of you.. While at WM one day I looked at the 6 HP Merc and found that to be a similar engine, It just had the Mercury logo on the very same engine cover and painted black. I'm new to this forum I'll look to see if I can send a personal message should I need your expertise.. Thank You and Fair Winds."

"Hello, I have a 4 stroke 6hp

"Hello, I have a 4 stroke 6hp Nissan outboard. Is there a way to adjust the low speed needle valve(jet)? If so, where would it be located on the carb.? If I set the idle stop adj. screw, either its too fast of it dies. So, I bought this motor to troll with, and it wont go slow enough. I though these things were suppose to go at slow speeds well? Also, it hesitates alot if you punch it from a slow speed, to full. I had it at the dealer and they tell me I'm nuts!!! I have been very dissappointed after trying to do the right thing and go 4 stroke to help the environment! It also "slips" at full speed. Perhaps cavitating and not getting enough bit in the water. I've tried all of Nissans props that are made for this motor and it didnt get better."

"Chris P.

(If I set the

"Chris P.

(If I set the idle stop adj. screw, either its too fast of it dies.)

This is exactly the same thing / problem I have. I wanted to troll my 22 ft sailboat on a calm day and had a hard time getting it to slow down to get the boat speed under 3 MPH without quiting. I found that if set the idle screw lower so that I can make it quit, but then pull the choke out the motor runs fast and so I then push in the choke to slow the motor down with out it stopping. I was able to get the boat down to 2 MPH ( GPS). I ran over 10 mile that way with never s miss.. It seems the idle screw adjustment is much to sensitive.
I am going to clean the carb rebuild the fuel pump and clean the screen in the tank. I bought the Service Manuel but not much trouble shooting there but a good schematic of the dis-assembly of the carb. Having trouble finding a rebuild kit for the fuel pump. I will watch and see what replies you get Chris"

The low speed jet is fixed and

The low speed jet is fixed and cannot be adjusted. Clean the carb by soaking it in carb cleaner. Then try it again. This model engine does get down to 1100 RPM at the lowest throttle setting.

Thanks Tohatsu Guru

Thanks Tohatsu Guru

"Yesterday ( Sunday )

"Yesterday ( Sunday ) was work on the Nissan OB 5hp 4-stroke day. Armed with the Tohatsu shop Manuel carb kit and new fuel pump and freshwater impeller kit, My brother and I proceeded to fix the bumpy and lousy idle.. When I went to troll last summer the motor ran and pushed our O'Day 222 at 3 MPH ( GPS ). Turned out to be a dirty carburetor as we found plenty of dirt. Information we got from the shop manual helped but it was not elaborate. Mostly common sense got us through the job.

When finished ,we squeezed the fuel bulb, pulled the choke and started on the second pull. Right away we could tell the difference. Warmed up it did infact slow down to a nice low idle and we were shifting in and out and through the gears without stalling. Big improvement! So THANKS TO EVERYONE for your sharing your knowledge and experience. Have one more question and will post next."

"I'm having slightly diffe

"I'm having slightly different issues with my 99 nissan 5hp outboard. this motor is "new to me". I've rigged it up to run as a kicker motor and I'm running the fuel line out of a second port on my 10m fuel filter/seperator.

the motor runs fine for a while but eventually it starts to stall out and I have to re prime the ball valve then its ok. it seems to get worse the longer I troll. once it gets "bad" it doesn't matter if I'm trolling at slow speeds or high speeds, it seems to loose its prime. my big motor doesn't have any issues.

I've re-rigged the line and checked for leaks. it seems solid. I've also changed out the fluids and the small fuel filter under the cowling.

does this small a motor have enough pull to draw fuel through this 10 micron filter? or could it be an issue with the carb or fuel pump?

my next move is to try running off a small tank with no 10 micron filter.

any thoughts are appreciated.

Aaron"

Yes on all three. Having to pu

Yes on all three. Having to pump the ball back up is an indication of a problem before the carb. Think fuel pump to tank.

quick update. (thanks for

quick update. (thanks for the help).

I used the motor with an external tank. Same issues. I was pretty sure that it was the fuel pump. Took the fuel pump apart and there was obvious issues (build up and perforations in the membranes).

ordered a new fuel pump. took me 2 minutes to replace. ran the motor through my 10m fuel filter.

no problems..started up ran better than ever. trolled around for over 30min without any issues or fuel line bulb deflating.


thanks for the help.