I have a problem with my 5 HP Nissan outboard. It came with my boat last summer. It has never run smooth. I took the engine to get it tuned up with no improvement. The engine did not improve. I learned that I knew as much about small boat engines as he did, which was not a lot. That lesson only cost me $50.00. I have checked the oil, changed the spark plug, added some dewatering treatment, checked the carborator (very clean). As a matter of fact, the entire engine is extremely clean. I can get it running but it chocks itself out if I let it run for a while. When it shifts it into FWD it almost always dies. There also seem to always to be an excess of fuel going into the engine (gas on the water). Second question, should I be adding oil to the gas? What mixture? 50 to 1? I am a sailing guy and this is my first outboard. Any help would be appreciated.
5 Hp Nissan trouble
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HOW ABOUT THE WATER PUMP
I had a similar problem, motor would run for awhile and then stop. Turns out the water pump impeller was shot. Unfortunately, so was the lower part of the motor so had to get a new one. And yes, I added 2 cycle oil to the gas. I believe it was 50:1.
I had a similar problem, motor would run for awhile and then stop. Turns out the water pump impeller was shot. Unfortunately, so was the lower part of the motor so had to get a new one. And yes, I added 2 cycle oil to the gas. I believe it was 50:1.
recheck oil/gas mix ratio
I had a Yamaha 8hp 2-cycle on my 22 way back when. I assumed it took 50:1 like the Johnson and Evinrudes I had owned previously, but it ran quite rough with that mixture. Turned out it used a ratio of 100:1....so I corrected the ratio and it ran extremely well.
I had a Yamaha 8hp 2-cycle on my 22 way back when. I assumed it took 50:1 like the Johnson and Evinrudes I had owned previously, but it ran quite rough with that mixture. Turned out it used a ratio of 100:1....so I corrected the ratio and it ran extremely well.
5Hp troubles
Thank you for the responses. I forgot to add I changed out the fuel filter and I will check the entire fuel line. I did some more research, it seems that 50:1 is the right answer. I will check the impeller. Thank you again for your responses and I will update as soon as soon get some results.
Thank you for the responses. I forgot to add I changed out the fuel filter and I will check the entire fuel line. I did some more research, it seems that 50:1 is the right answer. I will check the impeller. Thank you again for your responses and I will update as soon as soon get some results.
Jets get gummed up.
I have a 8 hp Tohatsu (Tohatsu and Nissan make motors for one or the other) They are essentially the same engines. Anyway mine was running rough and wouldn't idle so I took it in to a boat motor repair shop. It turned out that the jets were clogged. One was completely clogged. Apparently the jets are very small on these little outboards and clog very easily from oil deposits. I have also been told to use a manufacturer brand 2 cycle oil like Nissan or Tohatsu rather than the generic stuff you but at West Marine or Wal Mart as the generic stuff can cause more gumming. For the amount of oil you use it is not that costly ($2.50 for 16 oz.)For the small amount you use in a year the shop owner isn't putting his kid through college on your oil purchases. Also make sure your vent is open on your gas tank so you are not pulling a vacuum on the fuel line and starving for fuel. Good luck.
I have a 8 hp Tohatsu (Tohatsu and Nissan make motors for one or the other) They are essentially the same engines. Anyway mine was running rough and wouldn't idle so I took it in to a boat motor repair shop. It turned out that the jets were clogged. One was completely clogged. Apparently the jets are very small on these little outboards and clog very easily from oil deposits. I have also been told to use a manufacturer brand 2 cycle oil like Nissan or Tohatsu rather than the generic stuff you but at West Marine or Wal Mart as the generic stuff can cause more gumming. For the amount of oil you use it is not that costly ($2.50 for 16 oz.)For the small amount you use in a year the shop owner isn't putting his kid through college on your oil purchases. Also make sure your vent is open on your gas tank so you are not pulling a vacuum on the fuel line and starving for fuel. Good luck.
Jets get gummed up
This is good info. I have heard of this before. Were you able to check this yourself or did you have to have someone in a shop do it? As I have stated earlier in this thread I am a little gun shy of repair shops. When you had the clog, did you have excess gas passing through the engine?
This is good info. I have heard of this before. Were you able to check this yourself or did you have to have someone in a shop do it? As I have stated earlier in this thread I am a little gun shy of repair shops. When you had the clog, did you have excess gas passing through the engine?
Had the shop do it
I had the shop do the carb work. I am a newbie to outboards and did not venture in there myself. There did not appear to be any excessive fuel passing through the engine but then again I didn't take the cover off. Ask around your marina to find a reputable repair shop. There is bound to be more than one in the DC area. If your at the lauch ask anyone launching a boat. They're not all snakes. Good Luck. Jonathan Costello Heeling Powers
I had the shop do the carb work. I am a newbie to outboards and did not venture in there myself. There did not appear to be any excessive fuel passing through the engine but then again I didn't take the cover off. Ask around your marina to find a reputable repair shop. There is bound to be more than one in the DC area. If your at the lauch ask anyone launching a boat. They're not all snakes. Good Luck. Jonathan Costello Heeling Powers
Carb gumming - counter measure
When I bought my first boat a long time ago, the seller advised me to shut off the fuel valve and allow the motor to burn the gas out of the carb and shut itself off. I don't know if that really works, but the Nissan 5 hp on my 1994 23.5 has been shut down that way for 10 years and is easy to start in the spring after many months of inactivity - with no service to the carb. Must be something to his advice. I have replaced the spark plug once or twice in those years. 50:1 on the oil. And I use whatever I can get at the store or WM.
When I bought my first boat a long time ago, the seller advised me to shut off the fuel valve and allow the motor to burn the gas out of the carb and shut itself off. I don't know if that really works, but the Nissan 5 hp on my 1994 23.5 has been shut down that way for 10 years and is easy to start in the spring after many months of inactivity - with no service to the carb. Must be something to his advice. I have replaced the spark plug once or twice in those years. 50:1 on the oil. And I use whatever I can get at the store or WM.
Thanks Ghery
I'll start running my motor with the fuel disconnected when I finish sailing for the day.
I'll start running my motor with the fuel disconnected when I finish sailing for the day.
same trouble
I have 5hp 4stroke Nissan on my 240. The second season it spent 2 months in the repair shop. When they finally discovered the problems, they were surprised. The valves has carbon buid-up. After getting that fixed , the repair shop said run nothing but Amoco high test. Let the motor run out of gas when you are finished for the day by disconnecting the fuel line. Good Luck
I have 5hp 4stroke Nissan on my 240. The second season it spent 2 months in the repair shop. When they finally discovered the problems, they were surprised. The valves has carbon buid-up. After getting that fixed , the repair shop said run nothing but Amoco high test. Let the motor run out of gas when you are finished for the day by disconnecting the fuel line. Good Luck
I had similar problem w old gas
My motor did the same thing and the shop said it was mostly due to the water pump impellor being very worn. Earlier the fuel line / filter started leaking but that was an obvious problem. The motor seems to be sensitive to old gas- (about a month). A little staybil in the gas can seems to help a lot. The shop advised that the motor is sensitive to the oil ratio, but in an effort to have fresh gas, I tend to run 35:1 and 93 octane because my lawn mower is 35:1 and I use the same gas can. Hope this helps.
My motor did the same thing and the shop said it was mostly due to the water pump impellor being very worn. Earlier the fuel line / filter started leaking but that was an obvious problem. The motor seems to be sensitive to old gas- (about a month). A little staybil in the gas can seems to help a lot. The shop advised that the motor is sensitive to the oil ratio, but in an effort to have fresh gas, I tend to run 35:1 and 93 octane because my lawn mower is 35:1 and I use the same gas can. Hope this helps.
Closing the air vent
Believe it or not , I had almost the same exact trouble with my nissan 9.9. and to actually get it to run smooth, all I had to do was close the air vent valve on the tank. Otherwise air kept getting into my fuel lines. I also run my motor out of gas, to prevent flooding the carb.
Believe it or not , I had almost the same exact trouble with my nissan 9.9. and to actually get it to run smooth, all I had to do was close the air vent valve on the tank. Otherwise air kept getting into my fuel lines. I also run my motor out of gas, to prevent flooding the carb.
More info on my 5hp
Well after a few more sails, some more playing with my outboard, reading the postings (thank you everyone), and talking to some local experts I tried the obvious, I started the engine with the hood off. What became obvious, was although the engine was running well, fuel was coming out of a hole on top of the carbeurator. I assume this is some type of discharge. Fuel started coming out when I started the pull starter and seems to continue when it is running. Anyone out there seen this before or know what I need to do next?
Well after a few more sails, some more playing with my outboard, reading the postings (thank you everyone), and talking to some local experts I tried the obvious, I started the engine with the hood off. What became obvious, was although the engine was running well, fuel was coming out of a hole on top of the carbeurator. I assume this is some type of discharge. Fuel started coming out when I started the pull starter and seems to continue when it is running. Anyone out there seen this before or know what I need to do next?
even more advice
I talked to another local expert, and he said that it sounds like I have a blown gasket in my carbeurator and need to replace it or have it re-built. Does this sound right to anyone else? Does anyone know where to purchase a new or rebuilt carbeurator? What should it cost me?
I talked to another local expert, and he said that it sounds like I have a blown gasket in my carbeurator and need to replace it or have it re-built. Does this sound right to anyone else? Does anyone know where to purchase a new or rebuilt carbeurator? What should it cost me?
A few ideas
Check the bolts that hold the carburetor to the engine. Sometimes (particularly on a one cylinder), these will vibrate loose and cause air to leak in and lean out the mixture. You said it runs rough. Sometimes, this is due to an improper mixture. Does it: 1) Rev up a little and spit (too lean) 2) General rough running and lack of power. Gasoline smell. (too rich) 3) Also make sure the spark plug is snug and has the proper gasket (copper ring). A loose plug can give the symptoms you described.
Check the bolts that hold the carburetor to the engine. Sometimes (particularly on a one cylinder), these will vibrate loose and cause air to leak in and lean out the mixture. You said it runs rough. Sometimes, this is due to an improper mixture. Does it: 1) Rev up a little and spit (too lean) 2) General rough running and lack of power. Gasoline smell. (too rich) 3) Also make sure the spark plug is snug and has the proper gasket (copper ring). A loose plug can give the symptoms you described.
You can rebuild it yourself
Rebuilding the carb on these smaller motors is much simpler than for a larger motor or an automobile. I think that's why there isn't a market in rebuilt ones like there is for cars. A carb kit for a 5hp motor may cost less than $25, and consists of the appropriate gaskets and needles. The total labor time to rebuild it should be an hour or so. Elapsed time may be a day or more if you need to soak the parts to eliminate varnish, which is likely. A good outboard shop would do the rebuild for you (I would guess about $100) if you don't feel confident to try it yourself. With the symptoms you describe it's possible that something is warped or broken that is causing the leak, and that won't be fixed by a simple rebuild. You would then be forced to get a new or rebuilt carb. Good luck!
Rebuilding the carb on these smaller motors is much simpler than for a larger motor or an automobile. I think that's why there isn't a market in rebuilt ones like there is for cars. A carb kit for a 5hp motor may cost less than $25, and consists of the appropriate gaskets and needles. The total labor time to rebuild it should be an hour or so. Elapsed time may be a day or more if you need to soak the parts to eliminate varnish, which is likely. A good outboard shop would do the rebuild for you (I would guess about $100) if you don't feel confident to try it yourself. With the symptoms you describe it's possible that something is warped or broken that is causing the leak, and that won't be fixed by a simple rebuild. You would then be forced to get a new or rebuilt carb. Good luck!
2 cycle oil
A couple of years ago, while first venturing into the giant scale R/C planes, I asked what oil everyone was having good results with, since they all use 2 stroke engines ranging from 23cc to over 100cc displacement. Remember now, if you get a "flame out" due to engine fouling you could easily be writing off a toy that costs over $5K! The universal response was Lawn Boy Ashless 2 stroke oil. You can buy it at lawn mower shops. Since using it, I've never seized an engine, and when you pull the head, it looks just like new. "Try it...you'll LIKE it!" Bob Cowgill Cocoa, Florida H216
A couple of years ago, while first venturing into the giant scale R/C planes, I asked what oil everyone was having good results with, since they all use 2 stroke engines ranging from 23cc to over 100cc displacement. Remember now, if you get a "flame out" due to engine fouling you could easily be writing off a toy that costs over $5K! The universal response was Lawn Boy Ashless 2 stroke oil. You can buy it at lawn mower shops. Since using it, I've never seized an engine, and when you pull the head, it looks just like new. "Try it...you'll LIKE it!" Bob Cowgill Cocoa, Florida H216
2-stroke
I have a 4 horse Yamaha that I use on my dingy, I have had this engine for 20 years, and it still runs perfectly. It has a 100 to 1 oil-gas ratio, but it would still run well with a 50-1 ratio. I don't know about your engine, but one big distinction with mine is that it is water cooled, therefore it takes a higher grade oil because the engine runs much cooler than an air cooled engine. I have always used the Yamaha brand oil. The only thing that has been done to this engine is that when it was about 10 years old, I had all the gaskets and rubber things replaced. ajp
I have a 4 horse Yamaha that I use on my dingy, I have had this engine for 20 years, and it still runs perfectly. It has a 100 to 1 oil-gas ratio, but it would still run well with a 50-1 ratio. I don't know about your engine, but one big distinction with mine is that it is water cooled, therefore it takes a higher grade oil because the engine runs much cooler than an air cooled engine. I have always used the Yamaha brand oil. The only thing that has been done to this engine is that when it was about 10 years old, I had all the gaskets and rubber things replaced. ajp
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