1971 4hp Johnson

[bigred7469]

I was running this outboard and at about 3/4 full power it just stopped and I haven't been able to start it since. Bad gas? I changed the plugs even though they were not fouled. Getting good spark on the plugs. Could it be the carb? Any help would be great on what to check out next.





Red

 

[Daviet]

Re: 1971 4hp Johnson

If you have good spark, check the compression. If the compression is OK try squirting some fuel mixture into the carb and see if it will fire up. If it woun't fire up using fuel, check the flywheel key to see if it sheared.

 

[Rick.]

Re: 1971 4hp Johnson

You should check it with a spark gap tester to insure you have a good strong spark. I think Daviet above has you on the right course. My money is on the carb. if your spark is good. What is the history on the motor. Is it new to you, been sitting a long time, has the impeller been changed lately? Is there a chance it quit because of overheating? They are great little motors for sure. Best of luck. Rick.

 

[bigred7469]

Re: 1971 4hp Johnson

Yes its a New to me motor. But it was running this spring and now I can't get to fire up. I have no ideal when the impeller has been changed. I'm hoping think its either the fuel pump or the carb. It did fire up for about 20 secs last night after I changed the plugs and made sure they were gapped correctly but it never even got close to coming up to ideal it just barlley ran. The bulb on the fuel line will not stay firm so I'm guessing it is sucking in more air. Checked the fuel filter and it was clean and not gummed up. While we are on the subject where is a good place to buy parts/rebuild kits from? Thanks


Red

 

[Rick.]

Re: 1971 4hp Johnson

You can get parts here at Iboats or any brp boat dealer. Have you tried squirting gas into the carb. yet. If that helps then a carb. kit is your answer. Bulb. not getting firm tells me your needle isn't seating. Rick.

 

[bigred7469]

Re: 1971 4hp Johnson

So I'm guessing you just put a bit through the choke and give it a pull?

 

[Rick.]

Re: 1971 4hp Johnson

Yes into the carb. at the choke plate. Rick.

 

[bigred7469]

Re: 1971 4hp Johnson

Rick, I put some fuel into the carb at the choke plate and it started right up at the first pull then died out soon after. So I'm guessing I need to rebuild the carb. I also noticed and not sure why I didn't notice this before that fuel filter plastic piece that holds the screen is cracked on the tp of it so when you squeeze the bulb gas come flowing out of it and I do mean flowing. I need to replace that but do you think that will fix it with out rebuilding the carb? Thanks for the help

Red

 

[SolingSailor]

Re: 1971 4hp Johnson

Are you referring to the fuel pump? If so, yes, this is most likely your problem. Get a new one.

 

[Rick.]

Re: 1971 4hp Johnson

I agree this is a part that must be replaced. I would just buy a new pump considering the age of your engine. I have little doubt that is why it stopped suddenly (sucking air). Rick.

 

[hidef]

Re: 1971 4hp Johnson

Replace your fuel pump, plus both fuel lines under the cowl as well as your fuel line from the tank if they are not alcohol resistant. Rebuild the carb and run 24:1 at a minimum and 16:1 TCW3 if you don't mind the smoke. Unfortunately the 4 horse outboards from 67 to 78 did not have needle bearings only the brass bushings running 50:1 will eventually kill the engine. I just went through this with a 1975 4 horse it ran great at first and then the alcohol started deteriorating the fuel pump (i had replaced the fuel lines when I bought it). Now that all the fuel components are new or rebuilt it runs like a top again.

 

[bigred7469]

Re: 1971 4hp Johnson

Thanks for all the advice!! Does anyone know which part numbers these are? I just don't want to order the wrong one. Thanks again

Red

 

[hidef]

Re: 1971 4hp Johnson

You can get your part numbers from here. The fuel lines are 5/16 to the pump and 5/32 from the pump to the carb.

http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1971&hp=4&model=4136D

 

[Rick.]

Re: 1971 4hp Johnson

As a general rule of thumb I give the order desk my engine information and a part description. I let them look up the numbers. If there is a wrong part ordered (which can happen) the responsibility is theirs not mine. I do have a very difficult parts supplier that I have to deal with. Rick.