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20hp 1969 johnson> full power reverse but low power forward

C

coersum

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I bought a 1969 20hp Johnson outboard, the guy that sold it fixed it up, and it runs fine, starts good and everything but the forward speed doesn't seem to be right.

If I set it to reverse and go full throttle:
=> the motor and rpm go way up (by the sound of it) like a motor at full throttle should sound like.
If I set it to forward and go full throttle:
=> the motor go up only to about a quarter of the power reverse shows (maybe less) like it's limited in power. I believe he did install a new forward gear (I'll have to make sure).

Also once I go full on forward, it takes off a bit nicely but then kind of settles there. It idles very nicely too!

Wondering if maybe he installed something the wrong way which gives more throttle to reverse instead of forward? any idea ?

 
By design it can not go full throttle in reverse !----Sounds to me that it is only running on one cylinder.-----Check for spark that will jump a gap of 1/4" or more on both cylinders.
 
I forgot to mention, I can't seem to start it with the choke on, only with choke off, it's still in the mid 60's around here, is this normal ?
 
I will get a spark tester and compression tester tomorrow from autozone, do you think one of the coil is bad ?

In case it's needed, the model number is 20R-69D, what should the compression be at ? and in between the 2 cylinders ? if compression is good and one has no spark, this is the coil I need right ?
 
Ok so I checked compression on both cylinders top is about 102 and top 110. I also checked for 1/4" spark jump and got spark in both, blueish spark.

Kimcrwbr1:

Here is a picture of the bolts you talked about, I haven't taken it out yet, I was wondering if you knew somewhere with a more "for dummies instruction with pictures" :D
If not I'll try to follow your instruction. Also, is there a special torq for when I put the bolt back on?



I took few more general pictures of the engine to show more details:


Aluminum prop I believe, not in the best of shapes.


Neutral


Forward


Reverse
 
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The sparkplugs indicate that it may be running on one cylinder.------Or the fuel pump diaphragm is ruptured and flooding one cylinder.
 
Do you say that because of the color of the tongue part color ? By eye they both looked the same, on the pictures, the light acted differently.
 
So I went back and took them out to take a picture in same time and they are different, one is a bit darker (the tip) and if you look inside, one is white, one is black (I didn't even notice the inside before). Could it be a bad spark plug or it's something worse ?

Just in case, I will get new spark plugs too, trying to find the matching champion on to the NGK B6S here: http://www.sparkplug-crossreference.com/convert/NGK_PN/B6S but it lists a bunch, are they all compatible ? (Champion J7 or J7J?)



Kimcrwbr1: yes I did 1/4" gap spark test, both were blue-ish sparks.
 
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The reason you have lost power I think is the cable running to other side of motor , that runs your revs the other side is just gears eg forward , reverse. I had same issue so I disconnected cable and manually moved revs up and down . All to do with cable.
 


Reverse neutral forward





Here is a cutout of the 3 images above to show the distance between them, they are just about equal (I did turn the prop to make sure to fully engage the gear).

If I try and hold the lever perfectly vertical, it doesn't match the notches of the switch lever.

Also if you look at this video on youtube, (1968 instead of 1969 like mine) but the lever doesn't go straight up in neutral and seems to be matching the way mine looks in all 3 settings.

Could it still be that it's not setup correctly at the coupler between the upper and lower shift shaft ?

Would anyone know the corresponding Champion spark plug for a NGK B6S?
 
racerone said:
Clearly there is a PROBLEM here.
Click to expand...

Any idea where the problem could be from ? Both cylinders have good compression and sparks, I haven't checked the fuel pump yet, I have been trying to find a fuel pump kit but can't find one for my model, iboat doesn't have it, I found this one on marineengine.com but not sure if it is compatible. I will most likely need the kit to put it back together right ?
 
Just got hold of the previous owner and he did not change the forward gear (might have been another motor I was looking at), but he did put a brand new fuel pump in it so there is little chance this is the fuel pump causing the problem.

I got 2 new spark plug and will try them tomorrow or the day after whenever I have time.
 
So I changed the spark plugs and took it to the lake to test since I can't test full throttle in my backyard and same result.

This time I took a little video, bit jerky but maybe that will shed some light:
 
First, I wanted to say thank you all for your help, I really appreciate it!

kimcrwbr1 said:
Put it in forward with the engine off and give it WOT. Two things must happen the timing advance under the flywheel should be all the way advanced to its stop and the throttle butterfly should be wide open. It also looks like the prop hub may be slipping pull the prop and with a felt marker make a line across the inner hub and the prop and then after your next sea trial pull the prop and see if it still lined up.
Click to expand...

1. I believe those two things happen when WOT, I know the plate under flywheel hits its stop. As far as throttle butterfly, I will take some pictures in the morning and make a post for it. It follows the plate under the flywheel to its highest point, and pushes down (on what I believe is the throttle butterfly), but I can push it farther down by hand, I tried it today on the water but it's VERY sensible, revs UP and make the motor die (pressing too fast). I can rev it up very slowly if I am very careful but hard to do while on the boat :)

2. As for the slipping, I'll be taking it out Sunday, so I'll make the mark and take some more pictures while the prop is off too.
 
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kimcrwbr1 said:
Have you tried different trim angles on the motor it also looks to be at the lowest trim. Push the bottom of the motor back until it lifts the front of the boat up. What size of boat are you pushing and about how heavy?
Click to expand...

I did, earlier on (couple of water test ago), I changed it from 2nd to 3rd notch:

to

Also, on that test, I had the whole family for a little ride so about 300lbs up front. I also asked them to sit closer to me to get the bow up a bit but didn't help (did same test when it was on 2nd notch). Should I try the last notch the farthest from the boat ?


After checking this morning, I was wrong, when full throttled, it doesn't hit the stop:



Here you can see when full throttled, the plate under the flywheel is at its highest point, yet, I can still push it a bit by hand:

Should the roller turning the butterfly open be on top of that flat part of the plate ? (it would then I think hit the stop and push the butterfly opening to full). Not sure how to adjust that though.





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racerone said:
Post # 11 indicates it may be running on one cylinder.
Click to expand...

While running, I pulled one spark plug connector out, stuttered a bit at first but stayed running, then put it back and pulled the other, same thing happened. If it was running on only one cylinder, shouldn't it have died ?
 
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