70 hp Johnson wont accelerate

[skkool]

My 70 hp Johnson will start good and run great but when I stop to fish it wont accelerate. It just fall flat. If I keep messing with it and sometimes hit the choke it will take off and run like hell again until I stop. Rebuilt carbs already and have no hair left!! Thanks,

 

[Crosbyman]

mdl # year manuf ?

hitting the choke fed it some extra fuel so it looks like fuel starvation
venting OK on te thank .... no air leaks tank to carb ?

looks like old style carbs... how good did you clean the HS jet behind that lower bolt on the carbs

 

[jimmbo]

Welcome to iboats

A year/Model # would be nice as it allow us to determine if there is a Choke or other Enrichment System.

 

[skkool]

mdl # year manuf ?

hitting the choke fed it some extra fuel so it looks like fuel starvation
venting OK on te thank .... no air leaks tank to carb ?

looks like old style carbs... how good did you clean the HS jet behind that lower bolt on the carbs

I believe its a 1983 Evinrude 70 hp. I clean the carbs and blew out the jets with carb cleaner and then compressed air. The tank are replacements, plastic and yes the vents are opened. The primer ball stays solid. So I don't think there is a fuel leak before its started. I don't see or smell fuel either. I put on a new primer ball assembly. It runs great once you get moving so I don't think it could be a fuel pump issue. I put on all new fuel lines also. It has gotten worse as time goes by. Could it be the fuel pump isn't strong enough at idle?

 

[jimmbo]

That is an 83 Evinrude

 

[jimmbo]

You can test the Pressure the Fuel Pump is putting out. It is not very high at the best of times.
Most bog problems with these engines are Leanness. Low Fuel Level in carb(s), lean idle adjustment, dirt/gum/varnish in the carb. You had the Carbs off, incorrect sync between the Carbs and also the Ignition Timing

 

[Crosbyman]

seems they only made them from 1974 to 1979 what is your mdl # ??

 

[jimmbo]

View attachment 360774

seems they only made them from 1974 to 1979 what is your mdl # ??

The 70 was produced for many more years than that, till at least 2000

 

[Crosbyman]

yep wrong list range" :-(