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1983 Johnson 70hp troubles

Egobbo

Egobbo

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Hey guys, first time poster. been reading here alot. So i was gifted a boat, which needed a full rehab, floors stringers and transom. Finished that up, and now onto the motor. I was told that she was a good runner, by the previous owner, who is a longtime family friend. He owned it for over 20 years. Anyway, It sat for about 7 years, Ive completley gone thru the fuel system, sonic cleaned carbs, new lines, new tank etc. I still cant get this thing running right. Idles great in the water, under load it will move under its own power, till about 1/4 throttle, then bogs out and shuts off. Ive had the boat take off and get up on plane twice so far and seemed like it would stay running, but i didnt want to get too far away from the dock. Found bottom coil arcing thru case to block so i replaced it. I have the factory manual and im trying to do the link and sync. According to manual base timing should be at 4 deg. I can get it to 2deg, anything more and it starts running poorly and timing light goes haywire. Compression is good at 120 across the board. water pump, thermostat, fuel pump is all new. Carbs have been thoroughly cleaned, and lines have been replaced. Any Ideas? Im stumped...
 
Throttle linkages between the carburetors should be set so that "all" butterflies start to open at the same time and shut at the same time.... you do not want say two butterflies completely closed and one ever so slightly open. At full throttle, all butterflies must be completely horizontal/open.

The throttle butterflies (all) should just start to open when the scribe mark on the cam is dead center with the center of the throttle roller.

The throttle roller should be approximately 3/8" in diameter. If it is only about 1/8" in diameter, it is a two piece roller that has shed its outer shell... replace it.

The above takes care of the link & Syncronization setup UNLESS someone has changed the measurement between the vertical throttle arm and the metal cam which would make the idle timing setting impossible... in which case, adjust the threaded nylon yoke on the adjustment link to obtain that recommended idle timing with the scribe mark being dead center with the roller.
 
Joe, I have the OMC manual for an 82 which i was told is close enough. The yoke has been moved. I was trying to set ignition timing, by just adjusting yoke and was going to reset carb roller after i got ignition correct. I think my issue now is the fact that when i try to get ignition timing to 4 degrees as per manual, the timing light goes nuts and motor starts running poorly, i can get it to 2 degrees and she purrs like a kitten.
 
Egobbo said:
Joe, I have the OMC manual for an 82 which i was told is close enough. The yoke has been moved. I was trying to set ignition timing, by just adjusting yoke and was going to reset carb roller after i got ignition correct. I think my issue now is the fact that when i try to get ignition timing to 4 degrees as per manual, the timing light goes nuts and motor starts running poorly, i can get it to 2 degrees and she purrs like a kitten.
Click to expand...

If you're trying to set the idle timing with the engine running... don't do that. It'll drive you nuts!

Remove the spark plugs, set up a spark tester rig of some kind and have the timing light on #1 of course. Now, set the idle timing at cranking speed. Then you can reset the cam scribe mark to the roller.
 
I would have never thought to do it that way. An older omc tech suggested a power pack after I gave him that information. Like I said before, I've gotten it to take off and run wot, but that was with a buddy at the helm matting throttle control and me farting with the carbs. This thing is driving me nuts!!
 
No worries! I appreciate any advice your willing to give! I'm an auto mechanic, these outboards are like French to me!
 
Egobbo said:
After reading my manual again, should this motor at idle be timed 2-4° or at tdc?
Click to expand...

According to your service manual... TDC . Strange that I've never encountered that, not once that I can remember. However, I just double checked my 1983 70/75hp service manuals and they state the same thing.... the idle timing is to be set at TDC instead of a degree setting as all of the other models. (Weird!)... never too old to learn something huh?

Ar any rate, at that TDC setting, that is where the scribe mark on the cam is to be lined up with the center of the throttle roller via the nylon yoke adjustment and the lock screw at the roller assembly.
 
I'm going to try and re time it this afternoon and see what it does. Hopefully it solves my problem! Would a power pack cause similar symptoms?
 
So I tried the link and sync again , this time setting it to TDC... It doesn't like to idle in the water now, but, if I shift it into gear and give it a fist full of throttle she takes off and runs like a banshee. Ran it for a good 10mins. Seems like its loading up. Rev it a few times with the lever, and she takes off again. Safe to say I need to rebuild the carbs, pull the Welch plugs and really go nuts with these things?
 
On a flushette, the idle rpm should be, depending on the engine's shaft length...............

20" Shaft = 1000 rpm

25" Shaft = 1200 rpm

The idle will drop to its proper rpm when in the water.
 
it would not idle once in the water. idled good on ears. noticed a large amount of fuel puddling on the throat of the carbs. Starting to think its overfueling at idle and midrange and choking itself out. Once i get it on the main jets it flies.
 
With the carburetor face plate removed.... hopefully none of the carburetors flood when the duel primer bulb is pumped up hard.

I'll look into all of the jet sizes in the morning... alarm is set right now.
 
Make sure that the jet sizes are correct and in their proper location. All of the jets are marked/imprinted with the abbreviated size of their inside diameter. Note that "all" of the jets on this model meter fuel, not air.

Idle Jet = Extreme top front of carburetor - Part #325829 - Marked 42 - Size .042

Intermediate Jet = Starboard side of upper carburetor body - Part #327740 - Marked 68 - Size .068

High Speed Jet = Bottom center portion of float chamber - Part #321108 - Marked 52D - Size .052

(Carburetor Float Setting)
(J. Reeves)

With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.
 
Went thru carbs again today, pulled out Welch plugs, found some crud, cleaned and reassembled with all new everything. Now it will idle good in water, stalls when I put it into gear. Went to adjust idle and got shocked. I have no idea where it came from, or what caused it. I am officially at the end of my rope. A friend of my mother in laws owns a Johnson dealer and he's willing to take a look at it . hopefully he has some answers. Its just aggravating me cause I know it will run well, I just can't figure out how to get it to do that all the time.
 
So after fiddling with this thing I've come to yet another road block. Got it running great at idle, midrange bogs, if I rev motor on high idle a few times she takes off and runs great. Is there a mid range jet in these carbs? Everyone I talked to said its a lean condition..... Still stumped.
 
Lots of good advice from experts that know more than I'll ever know, but let me add my 10 cents:

I had something similar with my 1990 Johnson 115, went through a lot to figure it out, and good thing, because it gave me the time to think that with all those flaws, maybe it is also not cooling well. I put an infrared gun thermometer on it and discovered the engine was overheating in just a few seconds on the flushette. Had I run it in the water that day it would have run perfect from idle to WOT, and would fried the engine. Living in Florida, I've had 9 used engines in the last three years and 7 of them had clogged passages.

The carb jets must be cleaned individually with spray isopropyl alcohol (CRC makes it in spray) with a straw till it comes out clean the other side. The manual also said to use like max 40 lbs (?) of compressed air, though I never did it that way because you can't see if it is clear like you can with liquid going through it.
 
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