79 Johnson 70HP Fuel Pump & dying when shifting

[jzwatkins]

Hi all, I have been working with a 79 Johnson 70HP I got about a month ago. I changed the plugs, and cleaned it up, and changed the fuel line. The bulb looked okay, and looked fairly recent. So I have a few issues. I installed a filter in the fuel line so I could easily see the fuel and flow. When the engine is running, it's not drawing fuel very well. It's barely coming out at a trickle and isn't keeping fuel in the filter chamber. Should the fuel be drawn faster? I know that the diaphragm pumps only draw so much, but I'm still new to outboards.

Secondly, it requires to warm up quite a bit, before I can get the choke down to a good idle without it dying. Usually then when I try forward throttle it dies as soon as I try to ease the throttle forward. I restart it and it does just fine after that. When it happens it almost sounds like my RPM's are too low and it stalls out. Any other suggestions?

 

[racerone]

Fuel filter does not need to be full at all times .------------And report the results of a compression test.---------Is there a thermostat installed in this motor ?

 

[emdsapmgr]

A low idle can be a problem on those 3-cyl engines. Esp yours, which is only 49 cubic inches. The factory would have you set the idle between 650 and 750 rpm's when the boat is floating normally in the lake, and the engine is shifted into forward gear. You cannot set the idle when the boat is out of the water on the trailer. My 1990 is a poor idler, so I actually have my idle turned up slightly to between 850 and 900. Keep in mind that after just starting, you may need to occasionally re-choke the engine till it warms up, usually in the first 2 minutes of cold-starting. I added a white in-line fuel filter to my main fuel hose, as you did. It may be full when you first prime the bulb to start in the morning. Once the engine starts to draw fuel thru the line, the filter does not stay full of fuel. That's normal.

 

[jzwatkins]

It runs like a champ once it's warmed up. For the first few minutes I do have to keep adjusting the choke, but once it's warmed up I usually don't have any problems out of it. I know the fuel filter won't stay full, but it runs totally empty and then you can see that barely a trickle is coming out.