1979? 70HP Johnson Seahorse power/no power HELP

kevink82

Cadet
Joined
Apr 21, 2005
Messages
8
Hey folks, end of the season almost here and I am still trying to figure this one out. I have a very healthy 70 HP, 3cyl OB 2-stroke with 50:1 fresh fuel. Have only been in water 3 times. 1st started out with hardly any power maybe 5 mph. Did a little fishing then on way back to dock she kicked in to full throttle much to my pleasant surprise. A few short minutes later lost power again and dropped down to maybe 5 mph. A week later took the boat out again and no power the whole 15-20 minutes I ran it. Yesterday I dry gassed it, cleaned the fueal filter, sprayed carb cleaner in the carbs and took it back out. It was nearly as fast as when the power came back before but then within 3-5 minutes lost power again. I tooled around for 10 minutes and it never came back.

To note: While at loss of power I squeezed the primer bulb and nothing happened. All cylinders are firing but before I went out yesterday two of the plugs looked dry so perhaps they were not not getting fuel? After the carb cleaner spray they were fueled. The plugs are all new. Any ideas on a fix without the need to rebuild the carbs? Or am I even looking in the right area?

Another question, is there supposed to be any kind of air filter infront of the carb intakes behind the cover??

Is the name of my boat appropriate? "Total Malfunction"

Any and all help is appreciated! HELP THE NOOB!
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: 1979? 70HP Johnson Seahorse power/no power HELP

I would start off by checking the spark and compression. You said that all cylinders are firing, but how do you know this? Did you install an inline adjustable spark tester with the gap set to 7/16 of an inch and get a bright blue ZAP on all cylinders when cranking?

Spraying carb cleaner into your throats does FA. The carbs need to be removed and bathed/rebuilt for your efforts to be meaningful. I would invest in an OEM Service manual if you do not have one for this. Check out the FAQ for a thread by Tashasdaddy, it will help.

Good luck.
 
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