1983 Johnson 70hp sychronization problem??

mike2715

Recruit
Joined
Jan 13, 2012
Messages
3
Hi, I recently bought a 83 Johnson 70hp. Rebuilt carbs, changed fuel lines, changed plugs, compression is 132/140/130. My engine boggs down as soon as I reach about 30% throttle,,,if I pull back to idle and then hit the throttle all the way it comes to life perfectly and runs great. I have tried pumping the fuel bulb when it starts to bogg and the bulb is hard and it doesn't effect the engine. This problem is worst upon first start before the engine warms up. If I give it about 30% on the shifter and then open the carbs WOT by hand it responds, also it responds by blirbing the carb linkage only. In reverse it won't take hardly any throttle at all(but if I push the carb linkage it responds and revs all I need all the way to WOT). Does the problem exist because the timing isn't at the right spot? How does the timing advance when engine is cold? I guess it is the linkage sych? Does anyone have the manual pages for sych? Don't really want to spend the $ for a manual cause I'm probably not going to keep the boat. Thanks in advance for any replies have been losing sleep trying to fix this!
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: 1983 Johnson 70hp sychronization problem??

Is the timer base sticking ??
 

mike2715

Recruit
Joined
Jan 13, 2012
Messages
3
Re: 1983 Johnson 70hp sychronization problem??

When I move the linkage it appears to move fine.
 

kryan2

Petty Officer 2nd Class
Joined
Nov 23, 2008
Messages
193
Re: 1983 Johnson 70hp sychronization problem??

First let me start by saying "i aint no mechanic"......BUT>>> I just did the same and had the same problem. A 1984 75hp
with rebuilt carbs. Turned each air/fuel screw out 1 and 1/4 turns and it ran great on the hose/muffs. Got to the lake and it had no power after quarter throttle. Here's what we did. Wife was at the shifter/throttle and I was with screwdriver in each of the 3 air/fuel screws. We would start it, put it in gear (on trailer, backed in water) as my wife would slowly throttle up. It would die. I would open up each screw a quarter turn. We did this for 40 min till she throttled up, wouldn't die out and was trying to push my truck up the ramp. POWER!

You either have to take it in and have carbs adujstted or get it on the water and make your adjustments. Once it made power and would stay running we launched! I made final adjustments at full throttle on the water. She purrs now!

Good luck
 

mike2715

Recruit
Joined
Jan 13, 2012
Messages
3
Re: 1983 Johnson 70hp sychronization problem??

Thanks,,my carbs do notan adjustable air fuel screw,,,,it is a 70hp. Thanks for the reply though!
 
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