1987 Johnson 70HP Sudden power loss

Florianopolis

Recruit
Joined
Aug 18, 2005
Messages
1
New to forum. Bought motor 4 years ago. Fresh water. Ran great for two years. End of season year 2 did not winterize, garage kept. Beginning year 3 would not start. Mechanic rebuilt carb and bench tested motor ran fine and reminded me to winterize. I never used the boat after he rebuilt carb. <br />This year we launched the boat with new oil and fuel, a complete tune-up. The boat ran great for about 5 minutes at all RPMs. Then SUDDENLY went from 5,ooo RPM to zero. Engine would restart but only idle with full choke trottle advanced. Hence could not shift into gear.<br />Mechanic adjusted trottle and we thought the problem was solved. However once again boat ran great for 5 minutes at speed then sudden loss of power. This time the engine would turn over but not start.<br />We have done the following: new VRO pump, new fuel lines, new fuel bulb, new fuel and oil, new plugs. Today the mechanic called and said that the motor did the exact same thing again and he is at a loss as to what to do. So far about $1000. bucks in parts, labor and towing and still not running. I should add that I am only the second owner. Original owner based in Minnesota and boat got very light use. <br />Does anyone have a repair suggestion?
 

ob15

Chief Petty Officer
Joined
Jan 4, 2004
Messages
514
Re: 1987 Johnson 70HP Sudden power loss

I would think that the carbs need to be cleaned again.
 

midsized johnson

Petty Officer 2nd Class
Joined
Jul 28, 2005
Messages
155
Re: 1987 Johnson 70HP Sudden power loss

Did you or your mechanic check the ignition system? If it's original, you've got 18 yr old parts on there.
 

Goodoleboy

Chief Petty Officer
Joined
Nov 20, 2003
Messages
555
Re: 1987 Johnson 70HP Sudden power loss

My vote goes to either power pack or stator breaking down with heat build up. Possibly one or more coils breaking down under heat also.<br /><br />Good luck!
 
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