Logo
FULL SITE MENU

1984 Evinrude 70hp

M

mfisher0918

New member
I am at my wits end and hoping someone can help. I have a 1984 Evinrude 70hp on a 20ft pontoon boat. It idles fine but falls flat on acceleration. (Only in the water under load). I can "feather" the butterflies and get it to "catch" and then I can take it to full throttle and it runs like a champ. I can also engage the electronic primer to get to full throttle. This motor came off of a 14ft V-hull and runs perfectly on muffs.

Here is what I have done so far:

Rebuilt carbs, also took them back apart twice to double check and make sure everything is clean - it is. These carbs have fixed orifices so no jet adjustment

New plugs/wires

Checked resistance on all three coil packs - Good

All new fuel lines/primer

Rebuilt fuel pump - I believe it is working because pumping the primer bulb during attempted acceleration does nothing

Compression check - 125ish on all three cylinders

Spark test - good spark

Timed and synced per manual with timing light

I have no idea where to go from here. I have spoken to a talented Yamaha mechanic and he also has no answer.

Please help!?​
 
Try pumping the primer ball to see if it runs better. The fact pushing the primer makes it run ,points to a carb issue. How much of a gap between the roller and the cam is there?
 
I have tried pumping the primer ball and it makes no difference. I have also tried every combination of roller and cam gap there is. I probably adjusted it 50 times in an attempt to solve the issue.
 
Neither carb pick up tube (2,one inside the other) can be removed from what I can see. Everything looks spotless but wasn't sure if there were holes in those tubes that I can't see
 
Back
Top