Please help, 2 stroke NS18 problems

R3zrunn3n

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Mar 7, 2019
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Hi guys, I’m new. I purchased a Jon boat with a 2000 NS18, not certain exact model as it was apparently removed or worn off. I’m trying to do some maintenance and I have some problems

1) I would lose combustion, I’d be going at WOT and after 1 min it would drop to an idle and the engine ran really hard, sometimes turn it off and turn it back on to try to get it to work okay only for keeping the throttle just barely turned for a small troll.. fair amount of smoke...not good and did this for weeks and I just stopped using it.

i bought a carb kit, water impeller kit, lower stuff ever and I have a spare motor for parts should I need.

problem 1, my spark plug, the bottom one had some bad marks on the white section, compression test on both plugs is 150psi, oil was on both, running rich? Why would their be what looks like burn marks be on the white part? Trying to get my hands on service manual

i need to make my picture smaller than 2mb, I’ll work on that...thanks, sorry for long initial post
 

pvanv

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First, the Factory service manual is available. If you need one, PM me:
SERVICE MANUAL : 1 & 2 CYLINDER 2-STROKES

003-21035-1_lg.jpg
wAAACH5BAEKAAAALAAAAAABAAEAAAICRAEAOw==

Covers all 1 & 2 cylinder 2-stroke models.
Part #: 003-21035-1
List Price (MSRP): $50.00

Yours is likely an 18E or E2.

Next, that crud on the insulator of the plugs could just be old rubber from the plug cap, or it could be from some arcing if the cap isn't properly seated on the plug.

As for stalling out from WOT after 60 seconds, could be a few different things. Since compression sounds good, and the plugs look OK, I would start with the fuel system... from the tank all the way through the carb. A minor air leak at an o-ring in the primer hose could cause a lean-out that would cause your symptoms.
Also, a thermostatically-acting electronic bit could overheat after a minute of running hard, and cause poor ignition. Thermal intermittent problems can be very tricky to find, and you must test for failure while they are failing (hot in your case). Checking new plugs for color after having the issue might provide a clue.

Does it run OK at lower speeds?
 

Sea Rider

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Sep 20, 2008
Messages
12,345
Yep, if o'rings located inside both fuel connectors are dried, worn will suck air and achieve those mentioned sympthoms specially when running 3/4 to full throttle. Bear in mind that you are using a 18 old year original fuel line. As o'rings are not sold separately which is a crime, remove them with a thin needle and buy same at an auto shop, specify for gasoline use.

Install 2 new NGK BR7HS-10 or B7HS-10 spark plugs gaped tight to 1.0 mm. Sometimes installed spark plugs sitting for too long without use will tend to fail when the OB is demanded..50:1 gasoline/2 stroke TCW-3 oil is a must use...

Happy Boating
 

R3zrunn3n

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Joined
Mar 7, 2019
Messages
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Yours is likely an 18E or E2.

Next, that crud on the insulator of the plugs could just be old rubber from the plug cap, or it could be from some arcing if the cap isn't properly seated on the plug.

As for stalling out from WOT after 60 seconds, could be a few different things. Since compression sounds good, and the plugs look OK, I would start with the fuel system... from the tank all the way through the carb. A minor air leak at an o-ring in the primer hose could cause a lean-out that would cause your symptoms.
Also, a thermostatically-acting electronic bit could overheat after a minute of running hard, and cause poor ignition. Thermal intermittent problems can be very tricky to find, and you must test for failure while they are failing (hot in your case). Checking new plugs for color after having the issue might provide a clue.

Does it run OK at lower speeds?
[/QUOTE]

Thank you for response kindly. I'll definitely need a service manual and will contact you soon.
I planned on getting a brand new tank, fuel hose/ball, but you're also saying replace the small fuel lines inside the motor from the intake, to the filter and to the pump on the carb as well?

I'm hoping through all my engine service it'll kind of fix that issue : ( it's such a bummer.
It runs fine at a real low speed, correct! What does that tell me though?
should I also get a new thermostat? is that what you mean? sorry - I'm a little new but trying my best. thank you so much
 

R3zrunn3n

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Joined
Mar 7, 2019
Messages
21
Yep, if o'rings located inside both fuel connectors are dried, worn will suck air and achieve those mentioned sympthoms specially when running 3/4 to full throttle. Bear in mind that you are using a 18 old year original fuel line. As o'rings are not sold separately which is a crime, remove them with a thin needle and buy same at an auto shop, specify for gasoline use.

Install 2 new NGK BR7HS-10 or B7HS-10 spark plugs gaped tight to 1.0 mm. Sometimes installed spark plugs sitting for too long without use will tend to fail when the OB is demanded..50:1 gasoline/2 stroke TCW-3 oil is a must use...

Happy Boating

Thank you kindly for the response, I was hoping someone would tell me exactly what my model would be.
Where do O rings sit again? is there a particular size i'm aiming for?

EDIT: I think I get the O ring in my carb kit actually.. its the little bit bigger O ring with two smaller ones kind of attached to it?
 

TOHATSU GURU

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If it is a 2000, NS18E2. The O-rings are not available and they are not in a carb kit. You are supposed to replace the fittings.
 

pvanv

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If it is a 2000, NS18E2. The O-rings are not available and they are not in a carb kit. You are supposed to replace the fittings.

Yep. If keeping the old primer bulb and hose, you would get the complete fittings. Two different ones: one for the motor end, and the other for the tank end: [h=5]FUEL CONNECTOR - ENGINE/FEMALE (5HP~90HP 2STR & TLDI)[/h]
3B2702501.jpg

Female fuel connector - Engine side 8mm (5/16")
This is the connector that is installed on the fuel hose that connects to the motor.
Fits 5hp - 90hp 2-stroke models and and 40~90B TLDI models*.
Part #: 3B2702501M
List Price (MSRP): $20.73
[h=5]FUEL CONNECTOR - TANK SIDE : FEMALE (ALL MODELS)[/h]
3B2702810.jpg

Female fuel connector - Tank side 8mm (5/16")
This is the connector that is installed on the fuel hose that connects to the fuel tank.
Fits all models.
Part #: 3B2702810M
List Price (MSRP): $20.22
 

pvanv

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Messages
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Thank you for response kindly. I'll definitely need a service manual and will contact you soon.
I planned on getting a brand new tank, fuel hose/ball, but you're also saying replace the small fuel lines inside the motor from the intake, to the filter and to the pump on the carb as well?

I'm hoping through all my engine service it'll kind of fix that issue : ( it's such a bummer.
It runs fine at a real low speed, correct! What does that tell me though?
should I also get a new thermostat? is that what you mean? sorry - I'm a little new but trying my best. thank you so much
[/QUOTE]
Nope. The o-rings in the carb kit do not replace the primer hose o-rings. While you could have a bad line internal to the cowl, the likely leak is at the primer hose. If you buy a new one, it will come with new ends, so no need to buy the fittings separately. You may want a new fuel filter. They do get clogged, especially if old, cruddy fuel is run through them.
I said nothing about the thermostat; If checking temperature, use an IR thermometer. At temp, the motor should be around 150F.
 

R3zrunn3n

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Mar 7, 2019
Messages
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Thank you guys for the information and being helpful. I’m buying a new tank and fuel line so I think I’ll be good, plus carb kit, fuel filter, I hope this helps my problems :( any other advice is welcome

wish I knew what’d cause the white part of the spark plug to look like that??
 

Sea Rider

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Sep 20, 2008
Messages
12,345
Was that 18 HP-OB used in fresh or salt water ? Some issues : Could remove the thermostat located at upper cylinder head and have a look at the TS condition, if severely salted, rusted install a new one. Ob will work much cooler. If both internal fuel hoses that deals with the fuel filter are dried, cracked install new ones. Don't need a new fuel filter, just clean the old one with carb cleaner, check fuel filter internal o'rings condition. Replace if dried, hardened or elongated from E fuel use..

If the complete fuel line is still flexible, much cheaper would be to remove both fuel connector's o'rings which are different diams and look for them at a auto shop, the rest of the 39.00 dollars you'll be saving not buying 2 new fuel connectors can invest then wisely on a new thermo, thermo gasket and fuel filter gaskets as well.

Spark plugs are darn cheap, $ 6.00 or bit less for both, plugs which achieve failing issues when the OB is in high speed demand are hard to diagnose, change them, it's a silly saving. Most boaters tends to look for something else and overlooks spark plugs with issues.

Click image for larger version  Name:	Tohatsu M18-E2.JPG Views:	1 Size:	95.4 KB ID:	10711796

If this OB is same as yours, it's a M18-E2 model...

Happy Boating
 

R3zrunn3n

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Joined
Mar 7, 2019
Messages
21
Was that 18 HP-OB used in fresh or salt water ? Some issues : Could remove the thermostat located at upper cylinder head and have a look at the TS condition, if severely salted, rusted install a new one. Ob will work much cooler. If both internal fuel hoses that deals with the fuel filter are dried, cracked install new ones. Don't need a new fuel filter, just clean the old one with carb cleaner, check fuel filter internal o'rings condition. Replace if dried, hardened or elongated from E fuel use..

If the complete fuel line is still flexible, much cheaper would be to remove both fuel connector's o'rings which are different diams and look for them at a auto shop, the rest of the 39.00 dollars you'll be saving not buying 2 new fuel connectors can invest then wisely on a new thermo, thermo gasket and fuel filter gaskets as well.

Spark plugs are darn cheap, $ 6.00 or bit less for both, plugs which achieve failing issues when the OB is in high speed demand are hard to diagnose, change them, it's a silly saving. Most boaters tends to look for something else and overlooks spark plugs with issues.



If this OB is same as yours, it's a M18-E2 model...

Happy Boating

hey man, seriously.. thanks for taking time to explain that .. I added some photos.. you think you can tell me what model that is by them? I give you props if you could.. the model/serial sticker was removed but I still have that other one, maybe something in there can give ya a lead? I've been going off the NS18E2 parts.. seems like its the same, I used it for my water impellar kit and it seems like it should work. I went ahead and bought a new gas tank and fuel line also, I probably could've saved a few bucks but honestly I don't mind as long as it makes that god awful problem I have at WOT from stopping!

Thank you again for the advice, Sea Rider I appreciate that a lot bro
 

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pvanv

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That should be an NS18E2. Beware that some of those Attwood tanks (which don't have any conventional vent) have a perssure/vacuum type cap can which can jam; If it does that, the tank will collapse under vacuum as you run, and then the motor will "run out of gas" and stall, especially at high speeds.
 

Sea Rider

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You're welcome R3zrunn3n,

Been there regarding the fuel connector's o'rings and spark plugs with hidden issues, first one drove me crazy for some time until tested a brand new fuel line. Yep yours is a M18E2 model with the older fuel filter version.


Click image for larger version  Name:	Tohatsu 18-1.JPG Views:	2 Size:	101.0 KB ID:	10712062

Newer one is much larger as seen on posted pic, works much better and clogs less with polluted fuel. If not that costly, change it comes complete. It's part 3B7-022300 (Fuel Filter Assy) Check that both plug's caps internal plug contacts are in mint shinny condition for top electrical contact.

PD: Don't forget the new spark plugs...LOL!!

Happy Boating
 
Last edited:

R3zrunn3n

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That should be an NS18E2. Beware that some of those Attwood tanks (which don't have any conventional vent) have a perssure/vacuum type cap can which can jam; If it does that, the tank will collapse under vacuum as you run, and then the motor will "run out of gas" and stall, especially at high speeds.

pvanv Thanks man! Holy cow that sounds EXACTLY what my issue is.. as wide open throttle it'll just lose all power, like its running out of gas, or some restriction but it'll stay on, just acts really strange.. then shut it off, pump it, start over etc etc.. really frustrating.. I noticed there was some "leaking" in my attwood by the gauge and fuel connection.. im wondering if it was the gas tank all along !!!!!!! -__- that's so annoying. Thank you so much for that info, i'll switch gas tanks, i'd hate to lose all my gas capacity by switching to the tohatsu gas tank 3.3gallon, the 6.6 gallon wouldnt fit.. but at least the connections would be solid and i think it vents okay... again, thank you!
 

Sea Rider

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Probably all the trouble is related to using a non Tohatsu fuel tank. I use a 3.3 Gal Tohatsu fuel tank with a 18 HP and can go boating for hours at 3/4 throttle. For extended boating usually carry 2-1 Gal containers, just in case...

Happy Boating
 

pvanv

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pvanv Thanks man! Holy cow that sounds EXACTLY what my issue is.. as wide open throttle it'll just lose all power, like its running out of gas, or some restriction but it'll stay on, just acts really strange.. then shut it off, pump it, start over etc etc.. really frustrating.. I noticed there was some "leaking" in my attwood by the gauge and fuel connection.. im wondering if it was the gas tank all along !!!!!!! -__- that's so annoying. Thank you so much for that info, i'll switch gas tanks, i'd hate to lose all my gas capacity by switching to the tohatsu gas tank 3.3gallon, the 6.6 gallon wouldnt fit.. but at least the connections would be solid and i think it vents okay... again, thank you!

You can unlock the fuel cap a half turn to see if that vents OK. If so, you have a bad cap.
 

R3zrunn3n

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Joined
Mar 7, 2019
Messages
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That should be an NS18E2. Beware that some of those Attwood tanks (which don't have any conventional vent) have a perssure/vacuum type cap can which can jam; If it does that, the tank will collapse under vacuum as you run, and then the motor will "run out of gas" and stall, especially at high speeds.

pvanv I can't thank you enough - that's exactly what my problem sounds like.. so, I've been reading into this since you brought it up and it seems like companies and the EPA work against each other which ultimately leaves us with ventless gas tanks from the 2011 zero-emissions policy.. which leads to the question, how the hell do you vent this Atwood gas tank? or what are some other solutions the experienced folks use? I like the attwood because its exactly 20" and fits perfect in my jon boat spot. I'm looking at one way valves, vents i can maybe install at the top of my gas tank? drilling a hole is cool and all but what about the water coming in? I need to install a water/fuel seperator as well I guess..

thank you again, seriously it's been a big eye opener!
 
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