79’ Evinrude 70 Bogging

jpjourdonnais

Recruit
Joined
Apr 13, 2025
Messages
4
I have a 1979 Evinrude 70 (70973R) when I put it in gear and give it throttle, it’s tends to bog down and die, after some finesse with the throttle I can get past it and it runs amazing at WOT. The other thing I noticed is it doesn’t like to idle at low RPM, it takes about 1200-1300 RPM in neutral in the water to keep It running while in gear in the water, if I put it in gear with the idle adjusted any lower, it dies. I’d like to try and get a lower neutral ideally because it shifts really hard at that RPM. It runs great on muffs. I’ve tried choking it and pumping the primer bulb when it stumbles and it makes no difference. It has a 13.75/15 prop on it that’s had the vents added per the OMC SB. It has new ignition coils, a new power pack, new spark plugs, new fuel lines, a good primer bulb. And the carbs have been cleaned recently.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
38,411
You start with a compression test.----Post the actual values you get on this 45 year old fine ( when new ) motor.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
38,411
Fuel pump diaphragm checked?----Reed valves checked ?-----Flywheel key checked ?----Perhaps throttle plates are opening too early.
 

Crosbyman

Vice Admiral
Joined
Nov 5, 2006
Messages
5,647
carbs cleaned recently... do you mean removed, orifices cleaned out float checked out etc...

these are old style carbs easy to clean up incl.. side channel for LS upper drip chamber under the die size plug which feeds fuel for idling properly .
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
13,631
Fuel pump seems okay, the diaphragm isn’t stiff or broken.
How do I check the flywheel key, and if the throttle plates are opening and too soon?
It is easy to see if the Throttle Valves are fully open, by looking down the Carb Throat.
A check of the Link and Sync will verify proper Carb Opening, in relation to Spark Advance. That needs to be checked and if needed, adjusted any time a Carb is taken off.
 
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