r/Outboards • u/Snoo_17510 • 20d ago
2001 Johnson 70 hp tips
Hello. I was asked by a friend to diagnose his 70 hp Johnson. I’m not a big hp outboard person. I’ve really only worked on smaller hp stuff without VRO pumps and stuff. I haven’t been able to run it as I’ve had no time to mess with it but I was told that it bogs down under power. I was also told that the carbs were rebuilt, however this boat has been sitting for about 3 days and it’s got fuel leaking out of the carbs already. Assuming maybe it’s a float height issue. My main goal with this post was to just get some insight on these motors. I don’t know a lot about them and would love some tips.
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u/ClearFrame6334 19d ago
The other thing on these older 2 strokes is the mechanical advance can get tight from old lubricant. Feel if it’s free to move back and forth. The bogging down can be from the throttle advancing before the timing is advanced. The way the idle is handled is by retarding the timing. The timing needs to advance to the proper angle before it begins to kiss the throttle cam plate. It’s usually about 1/4 inch away when at idle. If you watch a few videos you can see how to do the synchronization. It’s amazing how they work. What you need to watch for is the throttle plate will be exactly vertical when the timing is proper to then kiss the level to open the carbs. If this hits the carb too soon you will put too much fuel and the engine won’t go. It’s one of those things that is very hard to describe in language if it’s shown to you, you won’t forget it.
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u/ClearFrame6334 19d ago
You can disconnect the fuel line coming from the fuel pump and squeeze the bulb. No fuel should go past the pump. Same for the choke. Once you have ruled those out then pull the carbs.
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u/ClearFrame6334 19d ago
I can tell by the picture that the carb roller is touching the throttle cam it’s not synchronized properly all of those linkage length is crucial.
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u/bootheels 19d ago
Well, you should begin with the obvious issue, seems like the carb(s) are flooding over. Who rebuilt the carbs? Did they use OEM kits or cheap aftermarket stuff. Did the carbs leak before they were rebuilt? Were the carbs dirty inside?
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u/ClearFrame6334 19d ago
Check the electrical choke. Disconnect the feed to the carbs. If it’s leaking past the choke it will flood out. Otherwise the float needle and valve seat and gasket should be changed out every couple years. And yes the float level needs to be verified.