'77 Johnson 4hp dies after start

[david brum]

I did a major rebuild recently. The little guy starts fine and will run for about a minute, then surge and sputter out. If I pump the gas tank bulb when it starts to surge, it will settle down for about another minute.

I recently rebuilt the carb and fuel pump. I also did the head gasket, water pump, coils, points, etc.

I am running it in a trash can. Maybe I didn't notice it before, but it sure seems to make a lot of smoke and floating black debris.

Thanks in advance for any advice!

 

[skruff33]

Re: '77 Johnson 4hp dies after start

I did a major rebuild recently. The little guy starts fine and will run for about a minute, then surge and sputter out. If I pump the gas tank bulb when it starts to surge, it will settle down for about another minute.

I recently rebuilt the carb and fuel pump. I also did the head gasket, water pump, coils, points, etc.

I am running it in a trash can. Maybe I didn't notice it before, but it sure seems to make a lot of smoke and floating black debris.

Thanks in advance for any advice!

does your carbs have gasket were air would enter,,,or a diapram that may have pin hole i would start there,,,,sounds luike air entering

 

[david brum]

Re: '77 Johnson 4hp dies after start

You think a carb issue? I don't remember any diaphrams in the carb but I could certainly check to see if the gaskets are tight.

 

[Rick.]

Re: '77 Johnson 4hp dies after start

It sounds as though your running out of gas. Could be the pump rebuild (didn't get everything back in the right order), mis-adjusted float. Did you adjust the slow speed needle properly? Perhaps the slow speed circuit didn't get cleaned enough. Best of luck. Rick.

 

[david brum]

Re: '77 Johnson 4hp dies after start

Thanks Rick

The fuel pump rebuild didn't go all that well. The new gaskets seemed really cheesey when compared to the OEM ones. I think I'll get another carb rebuild kit and just buy a new fuel pump since they aren't that expensive.

I'm pretty sure I adjusted the slow speed jets right, but will check again when I do the rebuild.

Thanks again,
David

 

[Rick.]

Re: '77 Johnson 4hp dies after start

http://www.sschapterpsa.com/ramblings/OMC/OMC info.htm

There are some pretty good instructions here for the fuel pump rebuild. I'm just not sure if the 4 is the same but likely very close. Rick.

 

[david brum]

Re: '77 Johnson 4hp dies after start

Thanks again Rick. The diagram is pretty much the same, although it shows two extra gaskets that didn't come with my original. I can see that I did install the middle plate upside down. I'll try that before I buy another.

Do you know if all of the 2" square fuel pumps are interchangeable? I see lots available with all kinds on OMC numbers. I'm particularly asking because a Sierra pump is about half the price of a Johnson pump, but the numbers don't match up (even though they look the same).

Thanks again,
David

 

[Rick.]

Re: '77 Johnson 4hp dies after start

Some of the Top Guns on this forum regularly recommend the sierra pumps so I would not hesitate to get one. You might consider a new post to get their assistance to pick the right one. Hopefully yours will work after you make the adjustments. Rick.

 

[DJ]

Re: '77 Johnson 4hp dies after start

Are you sure you got the float level correct? Original float? If so, replace it.

With todays fuels, I've found it necessary to set the float level a bit "fat" or high.

 

[david brum]

Re: '77 Johnson 4hp dies after start

Thanks guys

Rick, I ordered a new Sierra fuel pump, just to be sure. Only 40 bucks.

DJ, I will try that trick with the float. This motor has never been reliable, so maybe that's been the problem all along.

Thanks for the ideas. I will report back!