Nissan ns18e2 want open up

[Cd jack]

I have a 99 nissan ns18e2 18 hp 2 stroke. The motor has run perfect for years but on a recent trip it was hard to get crunk and when it did crank would just idle and not open up and run. With the throttle wide open it is doing 25-50 percent and will eventually die out. My first thought was fuel related. I changed everything from new gas tank, new gas line, fittings and bulb, carb kit, all new seals and diaphrams and that hasnt changed anything. It will crank up and idle all day but as soin as you throttle up it boggs down. Pumping the bulb has no effect, pulling the choke out while running makes it go dead. Im thinking the next step would be electrical but i have no experience doing this and need some advise and opinions. Thanks in advance

 

[Sea Rider]

Re: Nissan ns18e2 want open up

Welcome to Iboats,

Yor are looking at a 15 year oldie. Could have any electrical part heating up and missing. Does it miss same cold or warm ? You could have a worn cylinder head gasket failure. Could be dried, cracked letting small water droplets pass to combustion chamber and engine missing badly. The worst gasket state cond along higher engine temp, the worst engine will miss specially 1/3 to wot and eventually will drop dead.

Head gasket won't stay in immaculate state forever, salt water will end wearing it sooner or latter. Head gasket should be changed each min 300 max 500 worked hours as a preventive maintenance, periodicty will deepend on low or high end use over time.

When engine fails will need to be done under corrective maintenance. Will need to pull powerhead from base as both lower head bolts are very diffficult to reach properly to be torque with a torque wrench, will need to buy a new base gasket along head gasket.

If going for a head gasket change take advantage to clean all internal water paths inside crank case & cylinder head, check thermo cond, replace if too salted, old or rusty, change plugs. Could even go for a state of the art internal piston & cylinder head de carbon as in pics.

Happy Boating

 

[Cd jack]

Re: Nissan ns18e2 want open up

It does the same hot or cold

 

[Cd jack]

Re: Nissan ns18e2 want open up

Also the motor probably has less than 100 hrs on it

 

[pvanv]

Re: Nissan ns18e2 want open up

What is the compression? Have you tested the ignition and fuel systems per the Factory service manual?

 

[Jon Boat Jim]

Re: Nissan ns18e2 want open up

Could it be a fuel pump problem?

 

[Sea Rider]

Re: Nissan ns18e2 want open up

Could it be a fuel pump problem?

Usually not with just 100 worked hours, unless main thin fuel diaphragm is caput, severely dried, cracked due to Ethanol fuels remaining for long time periods inside fuel pump. To ensure it's not a fuel pump related issue, when engine is about to miss or die, prime hose bulb accordingly, if engine stops missing or springs back to life, you have a fuel pump issue.

Change all internal diaphragms, as those are the only internal parts that usually wears off. Assume that engine was used on salt waters, right ? If so, have you rigorously flushed that engine after each outing with fresh water ? Have you tried running engine with new spark plugs and fresh fuel ? Is the tank's air vent opened when running ?

Usually when you have a clean tank, small mesh filter at lower fuel pick up tube, internal engine filter & carb in immaculate clean state including a new fuel hose. The only 2 issues left to look after would be electrical or mechanical related parts.

As mentioned before, you could have a Exciter coil, CD or Ignition coil intermitent heat related failure at any throtttle setting, those are the trickiest to find spot on unless you have at hand at least a Ignition coil spare part to swap for immediate test.

Happy Boating

 

[TOHATSU GURU]

Re: Nissan ns18e2 want open up

Test for fire on the plugs while running....Or just replace the spark plugs and try it.

 

[pvanv]

Re: Nissan ns18e2 want open up

Test for fire on the plugs while running....Or just replace the spark plugs and try it.

Yup, I forgot that the plugs may have been overlooked...