1979 Evinrude 70 surge in power/loss of power

[huntingjustinlouise]

I have a 1979 70hp Evinrude on a 17' 1991 Tracker Pro Deep V. Occasionally the motor runs great all day.Most of the time the motor will run good then suddenly either die if in idle or lose power if running at speed.Ive also noticed the fuel bulb goes soft .I've replaced that line with no luck.If I squeeze the bulb sometimes it will stay running other times not. I know nothing about motors and any help would be most appreciated Thank you Justin

 

[ezeke]

Re: 1979 Evinrude 70 surge in power/loss of power

Are you using a portable fuel tank, and if so, could you describe it, please? <br /><br />It sounds as though you are not getting air into the fuel tank through whatever vent it has.

 

[huntingjustinlouise]

Re: 1979 Evinrude 70 surge in power/loss of power

Thanks for helping. The fuel tank is a rectangular 15 gallon permanent installation.The hose from the tank to the motor is the standard typ removeable hose like on most portable tanks use. ive replaced it once

 

[huntingjustinlouise]

Re: 1979 Evinrude 70 surge in power/loss of power

I forgot something important the motor only acts up when under load. When I run it with muffs and a hose itworks fine.

 

[ezeke]

Re: 1979 Evinrude 70 surge in power/loss of power

Next time the motor quits, get to the cylinder head quickly and feel for overheating.<br /><br />The pickup in the tank may be blocked and the vent could be blocked. I think running on a portable tank for a day would eliminate those concerns. Check to see if the vent screen for the tank has corroded. Just heard about a guy here who pumped and pulled a 100 gallon tank, only to find that the screen was blocked on his vent. <br /><br />Could be the power pack. Some will cut out when they are heated up. You can try to check that with a hair dryer blowing on the pack to see if it cuts out.<br /><br />You will also want to clean the ground wires on the coils and check all of the other wiring from the power pack to the spark plugs.

 

[Silvertip]

Re: 1979 Evinrude 70 surge in power/loss of power

Primer bulbs will not stay hard after the engine is running. Fuel merely passes through it by suction -- not pressure. The bulb must not collapse however. If it does there is a restriction between the pickup in the tank and the bulb.

 

[huntingjustinlouise]

Re: 1979 Evinrude 70 surge in power/loss of power

Thanks I will try these suggestions this week and let you know thanks again Justin