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Idle problem

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Inshore22

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Does this sound like a normal idle to you? Nissan NSF18B2 EF. I did not change the throttle at all during this video: https://youtu.be/qhAWk0u5EHA Had the tiller friction set as high as it could go and the vibration is still enough to turn the motor all the way.

A year ago the boat was running great and then on the lake it started sputtering and sort of revving and going forward and then not revving and slowing down randomly. Managed to get back to the launch and took it to Tohatsu authorized dealer and he said some debris must have gotten caught in fuel line. Had fuel system cleaned and a 100 hour service with carb kit, fuel pump, water pump, etc.

He def fixed something because it was usable after that even though it still wasn't running right. Was leaving a gas slick in the water. Long story short, for an unrelated reason and before I could get it back to the mechanic, had to have trailer and boat towed and it sat with gas (non-ethanol) in the motor for a month.

Then took it back to original mechanic and he said he missed a dry rotted fuel line the first time around and that he wasn't going to charge me cause he should have caught it and that is why it was leaking gas. Said it was fixed and I should be good to go.

But still doesn't seem to be running right to me. Using fresh non ethanol gas, new fuel line to gas tank and bulb and all the new stuff from the 100 hr service. Seems like it should be way smoother and not have that big vibration. I haven't had it in the water since the last repair because I've been doing fiberglass repair on the boat. Do I possibly need to do another carb kit even though I just had one done because it sat with gas in it for a month? Or is there something else obvious I should look into?
 
1. Idle RPM should be 1000 once fully warm. Yours sounds a little low.
2. You may need to tighten the nut on the tiller friction lever about 1/8 turn.
3. At 100 hours, you would seldom need a fuel pump; Possibly a carb kit, but usually just a good carb cleaning.
4. If you leave fuel in the carb for a week or two, you likely get some varnishing in the low-speed circuit. Best to open the drain screw and drain the bowl. Yes, at a month, the tiny carb passages likely have varnish. I bet it runs OK at higher RPMs.

See what it idles like once the idle is adjusted properly. May indeed need to clean the carb for a smooth idle. Check plugs as well. If black and sooty, replace them, and keep the old ones for spares.
 
Thanks for that.

As someone who doesn't have access to any specialized marine tools, what would be my cheapest way to measure my RPMs on the water with sufficient accuracy?

Would something like this work or is it just too cheap that it wouldn't be accurate? https://www.amazon.com/dp/B07K7LP3PT/ref=cm_sw_em_r_mt_dp_U_5OnMCb4STV79Y
 
I was thinking about giving the carb cleaning a go myself. Buy the repair kit and do it right. I've done a 2 stroke backpack blower carb before. Is this job much harder than something like that?
 
You may not need a kit -- but you might, so OK to have one handy. You also need a 1-gallon can of carb dip, available from auto parts houses. Do a complete disassembly, including jets and emulsion tube nozzle, then submerge all metal bits in dip overnight... then blow out with generic aerosol carb spray, then careful reassembly, paying close attention to float height. I would also get two carb base gaskets (there is a plastic thermal isolator, with a gasket on each side).
 
This should show you the base gaskets (7) and the insulator (8). They do not come in a carb kit:
002-21047-4_FIG04.jpg
 
Thank you. So is it correct that when I'm putting the carburetor back together the only adjustable parts that I need to measure before I take it apart are the screw that adjusts idle speed and the float height? Everything else only has one possible position if put in the right place?
 
Nothing is adjustable, aside from setting the idle stop. The float should be parallel to the carb casting when inverted. The idle stop screw will be adjusted by tachometer once all is reassembled and the motor is warm.
 
Thanks for the all the help. I followed your instructions this weekend and did the kit on the carb and it is much improved. When you say the engine needs to be warm to set the idle do you mean warm like idling in the driveway for 10 min before setting it or warm like cruising for 10 minutes before you set it?
 
Inshore22 said:
Thanks for the all the help. I followed your instructions this weekend and did the kit on the carb and it is much improved. When you say the engine needs to be warm to set the idle do you mean warm like idling in the driveway for 10 min before setting it or warm like cruising for 10 minutes before you set it?
Click to expand...
Ideally on the boat in the water. If that's not an option, in a test tank is probably OK. You can't set/check in-gear idle speed on muffs, because there isn't any water restriction on the prop.
 
Ah okay got it thank you. Once I've properly adjusted the throttle screw and while the motor is still warm, where should 1000 rpm line up with on the tiller handle? Start, restart, just above that?
 
Forget the location on the tiller handle throttle. Adjust the cables so that the carb is at WOT when the handle is all the way to fast, and all the way closed when at idle. The throttle stop will prevent the carb from closing completely.
 
Got it, I installed my tach and will get the idle set correctly this weekend. Is there any harm in using something like Quickleen (https://www.amazon.com/dp/B003ZF1GJQ/ref=cm_sw_em_r_mt_dp_U_4T1OCbRSHBSA7) now and then?
 
Inshore22 said:
Got it, I installed my tach and will get the idle set correctly this weekend. Is there any harm in using something like Quickleen (https://www.amazon.com/dp/B003ZF1GJQ/ref=cm_sw_em_r_mt_dp_U_4T1OCbRSHBSA7) now and then?
Click to expand...

Shouldn't hurt, but likely won't help, either. Just run fresh, non ethanol gas, and run the carb dry at the end of the day.
 
Okay thank you. For oil, I'm seeing 10W-30 mentioned in a few threads but there is a diagram in my owners manual that shows that for atmospheric temps above 85 degrees I should use 10W-40. I'm in NC so its pretty hot. Which would you suggest?
 
10w-30 mineral oil (non synthetic) is fine. Preferably type FC-W. You could run 10w-40 if that's all that's available. Won't hurt in hot weather. Truth is that today, even the cheapest oil available is better than the best oil was 40 years ago. Don't run synthetic. Nothing heavier than 10w-40, and never a drop above full on the dipstick.
 
Thought this would be a triumphant final post but no. Went out today got my idle set great. It seemed to be running really well. Tachometer seemed to be working at I was 1000 rpm idle in forward. At WOT I was at just a little over 6000 rpm. I was feeling really good about it. Stopped to eat lunch for about 45 min. After lunch I raised the motor out of the water to the highest setting and adjusted my anode (I mention this in case that could have caused an issue with a fluid draining or something).

Put the motor back down into the water and idled away. The motor had to still be warm because I ran for maybe 45 min to get to the island. When I'm accelerating from idle I feel a familar "missing". It was doing this before I did the carb kit too. And doing it in the same way as well -- not when cold but after the motor is warm and then shut off for a period of time like 15 or 40 min. Before I did the carb kit it was like I would open the throttle to halfway and there would be a delay where it would putter a bit and then all of a sudden it would accelerate to where it should be. Today at first it was kind of the same thing. Then my rpms crash and basically I can only idle. If I try to go over about 1200-1500 rpm's then I would get wild swings where it would be 1100 then 2300 then right back to 1200 then 2500 then 800 and then stall.

So I start idling back to the ramp. I idle along for an hour, stalling out at least half a dozen times, especially when I open the throttle a little to try to go faster than 1200 rpm. Then after about an hour everything is magically fine and the motor runs great all way back to the ramp. Rode for about 5-10 min back to the ramp with it working fine. I never went over 3/4 throttle after it magically began working because I just wanted to get back to the ramp.

So all I can think is I either:

1) screwed up the carburetor when I did that. But then why did it run so good on the way out?
2) this is a new problem
3) this goes back to the original blowout I had that caused me to take it in the very first time and that issue was never fully fixed -- there's a piece of hose stuck somewhere or something

Any ideas?
 
Could be a fuel starvation issue. Check every bit of the fuel system, from the tank strainer to the carb. If you have a bad o-ring in the primer hose, it can suck air instead of delivering fuel. Sounds like you got the carb done well, so I would look at the rest of the system. Check spark plugs -- they will tell you a lot. If bone dry, you are starving for fuel.
 
If the cause was not having the vent screw open enough would the primer bulb have gone flat? I had it open probably somewhere between 1/4 and 2/3 of a turn. It is possible that I fiddled with it a bit and that is why it ended up going back to normal, but I am not sure.
 
If the primer bulb goes flat, you definitely don't have much fuel flow. The motor is developing significant vacuum in the primer hose. Bad deal. That is usually caused by inadequate venting... but could also me a tank connector that is not all the way on, or a clogged tank strainer. If you have an EPA style tank, the vent could jam, so to test, crack open the filler a half turn to make sure you are venting OK.
 
I was pressed for time so I ended up just replacing everything the fuel delivery system up to the fuel filter. So when I got to the beach it was running great and idling perfectly at 1000 rpm. I put about 20 hours on it with maybe a little more than half of that trolling. About halfway through my trip I started to get some stalling while trolling and had to increase the idle speed a bit so I wouldn't stall. Is that normal for 10-12 hours of trolling? Would you say I need to clean or rebuild my carburetor again already?

In general though thanks a lot for all the advice in this thread it helped me keep the motor running smoothly through my trip and its still running well just idling at 1600 rpm.
 
Something is still amiss. Could be that the carb was not cleaned well enough to begin with. 1600 is pretty fast for idle. Make sure your tach is set correctly. Idle should be around 1000.
 
Okay, I did a full carb cleaning again and soaked it for about 4 hours in carb dip. This time I used compressed air to really get into every crevice whereas last time I just shot carb spray in there. So maybe this will do the trick. I'll update this thread when I know whether it worked. Thanks again for the help.
 
Back again. Been working on this and still don't have it right. Did 3 things:

1. After the last message when I went out to test it ran great at first. Then I tried to start warm and it wouldn't start. Took off the cover and saw gas dripping out of air silencer. I had wiped it with a shop cloth when cleaning which was dumb and I thought maybe I got some fibers stuck in a jet so:
2. Cleaned again even better and took out again and same kind of thing.
3. Got tired of this and didn't want to leave the boat for 2 weeks at the shop so bought a brand new carburetor. Took it out and it is running with one big problem. When I go from idle or low speed to higher speed I turn the throttle up and there is a long delay and then a sudden acceleration.

Over the last year I've replaced with oem parts just about everything in the fuel delivery system except a couple rubber fuel pipes. That includes the gas tank, entire bulb assembly up to the motor, the piece that connects the bulb assembly, the fuel filter, fuel pump, and carburetor.

At a bit of a loss here. Does this sound like fuel delivery issue?
 
If fuel was dripping from the air box, you are definitely flooded. That could be a float adjustment (hard to do with the plastic floats) or a bad needle.
It sounds like the accelerator pump is not working right. This is the chamber below the ABS solenoid. It has wee check balls that must be clear, and there is a passageway in the bottom of the carb which is difficult to clean, but if obstructed, will prevent proper filling of the accelerator pump chamber.
 
After the fuel dripping I just bought a brand new carburetor. I put it in and I'm not getting dripping but now I'm getting where I increase the throttle and nothing happens and then after a long delay (varies, 4-15 seconds or so on the day I tested it) and then a really sudden acceleration.

Does it sound like a fuel supply issue? Seems like I shouldn't have to look at a brand new carburetor?
 
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