Nissan 30HP 4-stroke Problem

[Ramjet]

Guys I have the above listed engine which is about 4 years old . The version I have has carburators and hydraulic tilt with stick steering . This unit is on a small freshwater fishing boat . On my last trip out the motor ran fine all day and then at the end of the day as you accelerated to about 1/3 throttle ,just as the boat came up the engine started to miss badly and would not go faster . I changed the plugs out but this did not help .When I put the new plugs in and checked the engine in the driveway it ran fine .It would accelerate to high RPM with no problem but in the lake with a load on it starts missing badly . A friend thinks I have a coil/ wire problem . Anybody have any thoughts ? I do not have a tach . Also the engine idles and runs smoothly at low speed .

FYI - I use this boat about 10 times a year and run the gas out after use . This engine probably has less than 50hrs on it .

 

[TOHATSU GURU]

Re: Nissan 30HP 4-stroke Problem

You have to check and see if you are loosing fire when the fault occurs. If you have fire, then have the carbs cleaned.

 

[thevigman]

Re: Nissan 30HP 4-stroke Problem

I have the same problem with my 2002 30HP 4 stroke. To date, I have changed the fuel, the fuel filters, fuel pump and thoroughly cleaned the carbs. My motor also runs fine while out of the water and will reach high RPMs. However, as soon as I put it in the water it bogs down and stalls once you give it throttle. At best, it will run rough but not go over 5 mph. Any chance one of the sensors could be defective or is it possibly a timing issue. HELP

 

[pvanv]

Re: Nissan 30HP 4-stroke Problem

A coil malfunction, while rare, is not out of the question. If there is a misfire due to an ignition failure, it will reveal itself in a wet plug for that cylinder. Verify oil is not overfilled, all plugs look dry and proper color immediately after the symptom occurs, and if all that's OK, the carbs probably need a proper soaking and cleaning.

 

[thevigman]

Re: Nissan 30HP 4-stroke Problem

Plugs all looked fine, oil was perfect and carbs were totally stripped down, soaked and thoroughly cleaned. Any further suggestions?

 

[TOHATSU GURU]

Re: Nissan 30HP 4-stroke Problem

It's time to break out the service manual and play

Which System Do I Want To Check First

Check for fire, check compression and check the gear oil. If all appear fine then start with the fuel in the tank and work your way through the complete fuel system.

 

[Wee Hooker]

Re: Nissan 30HP 4-stroke Problem

I would buy and install 3 of those cheap in line spark checkers and try running the motor in gear/loaded again. ( harborfreightdotcom has them) That way you can visually see if your getting spark break-up on the spot. If you see consistent spark on all three, you likely still have a fuel (or spark plug) problem.

p.s. I'm watching this closely as I have the 09' injected version of this same motor.