1977 70hp Johnson problem

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eyemaster

Recruit
Joined
Oct 23, 2009
Messages
2
Hello: I am new to this post and find myself needing some help with a motor issue. My outboard has two issues and they me be related in some manner. It seems lately that when I start it the first two or three times the engine turns real slow, and then after that it will start turning real fast and fire. After warm up we have had a problem with the engine slowing down by itself after we run for a while then after a few moments it will speed back up on its own. Can anyone help me.........thanks
 
Rudi2

Rudi2

Petty Officer 2nd Class
Joined
Aug 9, 2003
Messages
130
Re: 1977 70hp Johnson problem

Well, as far as cranking slowly-- how is yor battery? Is it getting old - is fully charged - are all connections tight without corrosion? The second problem sounds like a fuel issue--make sure you have fresh gas, clean or replace filter--maybe run some Sea-Foam in your tank. A carb rebuild might be in order -- just a few thoughts.
 
E

eyemaster

Recruit
Joined
Oct 23, 2009
Messages
2
Re: 1977 70hp Johnson problem

Thanks for the reply. I still haven't worked out this issue. I too thought it was a fuel issue with it or I have a coil breaking down when it gets warm. Replaced the fuel line with a new one this year and also checked the fuel filter. The squeeze bulb test when it is running slow does not make a difference. Plugs are changed in the motor every year and we use it quite often. The problem is that since it is so intermittent I can't even tell which cylinder it is because when I pull the plugs they all look the same.
 
R

RJDAWSON

Seaman
Joined
Sep 4, 2005
Messages
54
Re: 1977 70hp Johnson problem

You can do an ohms test on the stator and timer base and see if the reading are in range. I had cut out problems with my 1980 70hp and it turned out to be the stator. Stator resistance reading is 0.6-1.2.
 
F

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Re: 1977 70hp Johnson problem

eyemaster said:
Hello: I am new to this post and find myself needing some help with a motor issue. My outboard has two issues and they me be related in some manner. It seems lately that when I start it the first two or three times the engine turns real slow, and then after that it will start turning real fast and fire. After warm up we have had a problem with the engine slowing down by itself after we run for a while then after a few moments it will speed back up on its own. Can anyone help me.........thanks
Click to expand...

Urgent!!! check that motor for possibly getting water into the cylinders. When it sits, it rusts. If not fixed, it will soon completely destroy the powerhead.

A common leak is the exhaust cover gaskets (on the side of the block). They are prone to leak because the bolts near the exhaust ports are too far apart and do not support the inner plate which then warps.
 
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