Nissan Sporadic Performance

[Buzz457]

I have a recurring problem that?s hard to diagnose. I have a 2004 Nissan 15 hp, 4 stroke. Sometimes I can pull it and it starts fine the elect choke satisfies and it runs great. Other times I have to pull repeatedly and keep feathering the gas to get it to start and then continue to run. I can get it going usually and up to WOT but the engine cuts back a while getting to full speed and during full speed. It has a new carb, fuel tank, line, primer bulb and spark plugs. My first thought was to check the fuel filter and fuel pump but until I get time, does anyone have a better starting point? Also I thought it may be sucking air into the fuel system somehow, but how can you test that? Thanks in advance.

 

[TOHATSU GURU]

Re: Nissan Sporadic Performance

By new carb do you mean that you just purchased a new carburetor without knowing that if the old one was bad?

 

[pvanv]

Re: Nissan Sporadic Performance

I have a recurring problem that?s hard to diagnose. I have a 2004 Nissan 15 hp, 4 stroke. Sometimes I can pull it and it starts fine the elect choke satisfies and it runs great. Other times I have to pull repeatedly and keep feathering the gas to get it to start and then continue to run. I can get it going usually and up to WOT but the engine cuts back a while getting to full speed and during full speed. It has a new carb, fuel tank, line, primer bulb and spark plugs. My first thought was to check the fuel filter and fuel pump but until I get time, does anyone have a better starting point? Also I thought it may be sucking air into the fuel system somehow, but how can you test that? Thanks in advance.

Start by reviewing your Factory service manual, available at any dealer, including me. Then review/diagnose the mechanical, electrical, and fuel systems, with an emphasis on the fuel system. An air leak into the fuel line can commonly occur at the o-rings for the primer hose (either end) or at the fuel pickup in the tank.

 

[Buzz457]

Re: Nissan Sporadic Performance

I just put a new carb on at the begining of the summer to convert from a 9.9 to a 15. It ran fine after that for a while which makes me think its not related to that. I bought the motor used so I didnt have a manual for it. I downloaded what i guess is it and according to it, it could be anything related to the fuel system, which is obivious. I just wanted to know a good place to start. I replaced the fuel line from the inside of the meter to the fuel pump and added a new fuel filter and new plugs. Going to try and get off work a little early and go try it out.

 

[pvanv]

Re: Nissan Sporadic Performance

You need a Factory service manual (not the owner's manual -- which is available at nissanmarine.com) to assist you. The Factory service manual is copyrighted, so is not available for download; It's available from any dealer, including me.

 

[TOHATSU GURU]

Re: Nissan Sporadic Performance

Is the engine always on the boat or are you taking it off and on?

 

[Buzz457]

Re: Nissan Sporadic Performance

I put it on the boat earlier this year and other than when i was installing a jack plate it stays on.

 

[TOHATSU GURU]

Re: Nissan Sporadic Performance

Tough call. Probably still the carb, but it could be a weak ignition part. You can troubleshoot the ignition, with the manual, and at least eliminate that as a possibility. Other than that, back to the fuel system again and again and again.

 

[pvanv]

Re: Nissan Sporadic Performance

Agreed. Your primer supplies fuel before starting, so a weak fuel pump will not contribute to that problem. Likely needs to have the carb pulled, thoroughly disassembled, soaked for about 4 hours in real carb dip, blown out, and reassembled. While at it, check the ABS enrichment system.

 

[marineswarm]

Re: Nissan Sporadic Performance

I am not sure what year yours is but i have an older late 80's early 90's Nissan, and i have been haveing the same problem, basicly running like crap, when get full throttle runs all right and then falls on its face. Well after taking carbs off to make sure nothign gumed up, it was not. replaced the fuel line and bulb, was dry rotted a little. still same problem. I went to marine shop and got some of that 2-4 fuel conditioner. And i tell you what purred like a kitten, then i started putting higher octane fuel, and one heck of a differance. i think the the gas drawls moisture and the conditinor takes care of that, and higher octane means less moisure drawling. That helped me out so try that sir. and if its like a motor like mine, make sure your oil is being pumped properly, Just today mine quit and scored the piston sleeves, took off the head and dry as a bone, one cylinder has 30 LBS and the others have 120lbs. A very sad day for me.

 

[pvanv]

Re: Nissan Sporadic Performance

His motor is nothing like yours, and his problem is not related. OMC conditioner does nothing for water in the fuel. 87 octane is plenty; Higher octane does not affect water absorption. No "mechanic in a can" products will fix this kind of problem.