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70hp orifice change

Inspect / replace diaphragm in fuel pump.-----If you have a cheap plastic fuel tank then run with another tank and hose.
 
mikegonzo721 said:
Thank you Racerone, I'll repost the results.
Click to expand...
I found something upon my fuel pump inspection. The new fuel pump has an open hole between the 2 mounting screws, the mounting gasket has the same. The original does not. I purchased a rebuilt kit that was for this motor but...it was sized for the new pump that I was inspecting. Dungar Marine gas a video about servicing a Johnson evinrude fuel pump, and he talked about this hole in the pump at 12 minutes 20 seconds into the video. He says it's for vacuum. My motor does not have a vacuum port behind the fuel pump. It draws its pulse from another line at the bottom of the pump. I think this aftermarket pump should have come with a plug for the back and it would have worked fine. But I don't know! With the new aftermarket pump I was able to draw air and blow air through the hole! I think this is where my air in the lunes is coming from. I rebuilt the old pump and installed it. Pumped the bulb and it's holding pressure. I'll check in the morning if it leaks. If it doesn't I'm running out to the lake for yet another test. Fingers crossed I found my problem. If any of this post sounds incorrect please reply. I'll repost my results.
 
Last night's test run was partly a great success. This motor does not require the extra vacuum hole in the back of the fuel pump. I was able to cruise the lake, WOT. My problem now is a misfire.......
It mostly happens at mid range. With the timing light on I was able to see the misfire. I have new coils new wires new plugs and a new rectifier. The motor starts great and charges fine. I think it's time for a power pack. Any thoughts?
 
Racer, I am a bit impatient! I saw an ohm test from CDI for the power pack but it doesn't really go into detail. Am I supposed to disconnect the battery or spark plugs or anything else for that matter before I do this test? My new power pack will be here Sunday and in the meantime why not do some checking!
 
Well----12 volts from the battery has nothing to do with making spark for the plugs.-----It is the spinning flywheel ( magneto ) that makes the spark.
 
Better late than never! I finally received my power pack. The CDI trouble shooting guide was very helpful. I was able to test the old power pack with their direction. sensor 1 ohmed out at 87.8 ohms, sensor 2 at 119.5 and sensor 3 at 98.8. I checked the timer base as well and it tested within the parameters as far as the ohm test goes. I don't have a DVA adapter just yet but knowing how the motor ran before the power pack change, I have a hard time believing anything else needs changed just yet! Any thoughts or double check suggestions are very welcome. I'll repost my results after this weekend.
 
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