1977 Johnson V4 85hp runs perfect then suddenly loses power

[yabble]

1977 Johnson V4 85hp runs perfect then suddenly loses power, will run full throttle for about 40 seconds and then lose power, if i pull the idle up in time i can save it and bring it back up to full throttle again but the same will happen again also it sometimes runs great at idle other times it wont idle at all
I assume the carbs are properly adjusted because when it runs it runs sweet, i can only assume its the fuel line or pump? any help would be great.

 

[DargelJohn]

Re: 1977 Johnson V4 85hp runs perfect then suddenly loses power

When running does the primer bulb go flat? If so, you have a fuel restriction somewhere between the gas tank and motor.

 

[SparkieBoat]

Re: 1977 Johnson V4 85hp runs perfect then suddenly loses power

I always start with compression check, then spark test with a spark gap tester, just to eliminate any other issues. But you probably have fuel issue, either pump or fuel line sucking air or clogged vent..you will have to figure it out. If the motor shows improvement when you pump the bulb, while you are suffering power loss, that is a good indicator of a bad fuel pump, but I would eliminate fuel line connectors/cracked fuel line issues first. borrow a tank and fuel line from a friend that you know is good, and use it as a test to eliminate other issues, then rebuild fuel pump if needed.

 

[yabble]

Re: 1977 Johnson V4 85hp runs perfect then suddenly loses power

thought that might be the case, thankyou for your time ill let you know how it goes.