2000 Nissan NS30A4 30hp missing/wont get to full throttle. Out of ideas. VIDEO

[RY9]

I tried to buy my dad a little jon boat for fathers day, but his thing has been nothing but a headache. Its a 2000 Nissan 30hp 2 stroke NS30A4. I bought the boat/motor off craigslist. I test ran it on the trailer and it ran fine so I bought it. I figured how much could be wrong with a small simple 2 stroke. The motor starts right up everytime and will idle OK. Its gets to low/mid rpms fine, but when I go to full throttle it bogs/misses and wont reach full rpm. Ive searched high and low and tried a bunch of things with no progress.

https://www.youtube.com/watch?v=F7WV-ayjRg8


Heres what ive tried so far:

Compressing is good/even on both cylinders (around 125)
New coil (one coil for both plug leads)
New exciter coil
New alternator coil
New CDI
New plugs twice
New fuel (rec 90 with penzoil 50:1)
New fuel line connectors

I've tried disconnecting the shut off switch, no change.
The fuel pump will pump fuel when turning over the motor with the line off the carb.
The carb has been cleaned twice and looks good.
The plugs look kind of wet when I have checked them.(I was thinking maybe the fuel pump was leaking fuel past the diaphragm into the motor, but when I took the fuel pump off it doesn't seem to be leaking, but not 100%)
Pumping the fuel ball has no effect.

I'm frustrated and disgusted with the engine and myself for not insisting on a sea trial. Don't buy anything from a skinny short balding guy named Jason in Dania Beach FL.

Thanks

 

[fhhuber]

Checked the timing?

Verify that it hasn't fractured the key keeping the flywheel lined up correctly to the crankshaft. Being off some can let it run but you won't have power.

 

[RY9]

From what I can tell, its getting to the correct 25 degree mark at wot. I had the flywheel off to replace the exciter/alternator and everything looked good concerning the key. I have marks on the shaft/nut/flywheel to verify that nothing is slipping and it looks OK. Thanks!

 

[Sea Rider]

The engine bogs/misses same cold or hot and wont reach full rpm. When bogs, engine will die or just miss and keep on running ? When timing plate stops at 25? mark, do you have carb butterfly opened at 180 deg, check. How old is that engine ? If you have changed every possible electric part, you could have a faulty head gasket ? Compression won't tell much, engine has to be running at medium to high revs and load to miss, how badly misses will depend on how bad is that gasket.

Happy Boating

 

[RY9]

The engine bogs/misses same cold or hot and wont reach full rpm. When bogs, engine will die or just miss and keep on running ? When timing plate stops at 25? mark, do you have carb butterfly opened at 180 deg, check. How old is that engine ? If you have changed every possible electric part, you could have a faulty head gasket ? Compression won't tell much, engine has to be running at medium to high revs and load to miss, how badly misses will depend on how bad is that gasket.

Happy Boating

Engine runs the same weather cold or hot. The longest I have run it is only about 7-8 min at a time. When the engine bogs/misses it doesn't stall, just runs very rough. At wot, carb butterfly is open all the way. Engine is a 2000. I took the reed block off today and all of the reeds looked good with no damage.

One thing I did notice, was that there was no thermostat in the housing. The motor felt like it reached operating temp, so I am not sure if this could cause a problem like I am having.

Would I notice anything on a visual inspection of the head gasket?

Thanks for the reply.

 

[Sea Rider]

You need to install a new thermo along thermo gasket, engine will work much better at a controlled working temp. If installing a new thermo will cure the patient, noy sure, start by installing thermo test and see what happens.

A visual head gasket inspection won't tell a thing, not even while checking compression. As to undertand, with heat cylinder head expands and if gasket is faulty small water droplets will go inside combustion chamber and engine will miss, if severely faulty engine will shut off, when cools down will start right again to miss again. One issue that nobody performs is a head retorque from time to time as gasket will tend to compress itself and not seal properly.

Happy Boating

 

[RY9]

No Title

Well I took the head off. Complete disaster. Out of the 10 head bolts, 6 broke off into the head. The bolts seemed very weak. It didn't take much torque to snap them. The cylinders/pistons seemed to be in pretty good shape. It had lots of oxidation on the bolts and gasket.

 

[Sea Rider]

Gee....you have opened the Pandora Box. That's what I talk about when referring to head gaskets, everybody assumes that head gaskets are eternal and you won't even need to re torque head from time to time. You can see clearly how water have rusted all internal and external head parts and powerhead as well. Will need to remove all rust and file with sand paper both mating surfaces to immpecable clean and even cond to seal well along new gasket.

Head gaskets should be changed as a preventive maintenance which every body gives you know what, but everybody changes it as a corrective procedure once kaputt and has already made internal damage. I'm a big fan about retorquing head from time to time and changing head gasket each 600 meterd worked hours no matter if engine still runs as a champ, but that's me. You plan removing all those broken bolts by yourself ?

Happy Boating

 

[kevinwd1]

What are the torque specs are for the head bolts on a 2006 25hp tohatsu 2 stroke outboard

Regards Kevin

 

[Sea Rider]

30 Newton Meter, adjust with (3) steps of 10 NM increment till 30 is reached.

Happy Boating

 

[Sea Rider]

Was that 30 used on saltwater or freshwater ? If salted, bolts are seized due to salt...

The torque sequence is as follows :

9-10 Upper
5-6
1-2 Middle
4-3
8-7 Lower

All clockwise starting 1-2

Happy Boating