1976 Johnson 25 Stalls when given throttle

IM Buddy8 · Oct 11, 2012

I have a 1976 Johnson 25 that I just got running recently. It didn't have spark before so I swapped all the electrical with electrical from a power-head with great spark.

It will start right up 1st or second pull with the choke and after it idles for 10-20 seconds (or until a little warm) I can turn the choke off and it will stay idling. (at least 5 minutes it was idling).

If I put it in gear the rpm's drop pretty low and it will stay running but I can't give it any throttle or it dies out.

I'm new to boat motors, so any help would be appreciated. I haven't cleaned the carb yet, but if I do are their any passage ways I should make sure are extra clean?

Here is a picture of my throttle timing in neutral without any throttle. I see the two timing lines but I'm not sure what they are supposed to line up with..

Thanks,
Ryan

fireman57 · Oct 11, 2012

Re: 1976 Johnson 25 Stalls when given throttle

The first thing to do is give the carbs a good cleaning and I bet your problem goes away. I can't see your picture very well but the cam roller will line up between the two marks on the plate that it rolls on.

IM Buddy8 · Oct 11, 2012

Re: 1976 Johnson 25 Stalls when given throttle

fireman57 said:
The first thing to do is give the carbs a good cleaning and I bet your problem goes away. I can't see your picture very well but the cam roller will line up between the two marks on the plate that it rolls on.

Thanks I'll try to clean the carb out tomorrow AM. That roller wont go to in between those two marks? The picture was taken at no throttle and it's about 1/4 inch to the left of the marks. Is this normal? What gear should the motor be in when setting this?

AlTn · Oct 12, 2012

Re: 1976 Johnson 25 Stalls when given throttle

the throttle butterfly should just begin opening as the throttle cam roller rest between those 2 marks..neutral is fine when setting this

OptsyEagle · Oct 12, 2012

Re: 1976 Johnson 25 Stalls when given throttle

You could also try and set your carb rich/lean settings. It is possible that you are running too lean.

http://forums.iboats.com/showthread.php?t=167352

IM Buddy8 · Oct 12, 2012

Re: 1976 Johnson 25 Stalls when given throttle

OptsyEagle said:
You could also try and set your carb rich/lean settings. It is possible that you are running too lean.

http://forums.iboats.com/showthread.php?t=167352

I cleaned the carb this morning very throughly. At the bottom of the bowl where the main jet gets it's fuel from was very dirty with lots of little debris. After cleaning that out it started riight up second pull and it will idle all day long. I put it in gear and it held RPMS and I could rev it up. I can't rev too quickly though it seems like it's not 100% but only about 80-90% correct. Better than the 60% I'd give it yesterday.

Is there another adjustment besides the low speed jet? I've adjusted that one properly.

Also what is the correct way to adjust the idle on this engine?

As I mentioned before the roller will not go in-between those timing marks. At no throttle it is about 1/2 inch away. Is this normal?

Thanks,
Ryan

AlTn · Oct 13, 2012

Re: 1976 Johnson 25 Stalls when given throttle

the roller isn't touching the throttle timing cam?, or, it's touching the cam but won't rest between those marks when you have the throttle advanced as far as possible in neutral?...the roller should go beyond those marks, and the throttle plate should be slightly open when you have the throttle advanced as far it will go with the motor in neutral...then at wot in gear...the roller should be on the highest point of the cam and the throttle butterfly should be exactly horizontal in the carb throat

The idle is adjusted with the engine warm, pushing the boat in forward gear. It's a combination of idle mixture adjustment and adjusting the idle stop on the port side of the engine < tension spring and screw at rear of the tiller handle >.

At no throttle the cam roller may not even be on the cam.

To start the motor try full choke, motor in neutral, and the throttle advanced as far as it will go in neutral. After the tries to fire, kick the choke off and see if it'll start < you may have to go to 1/2 choke, depends >..when it does fire and run, reduce the engine speed and warm the motor up some before taking off.

IM Buddy8 · Oct 14, 2012

Re: 1976 Johnson 25 Stalls when given throttle

AlTn said:
the roller isn't touching the throttle timing cam?, or, it's touching the cam but won't rest between those marks when you have the throttle advanced as far as possible in neutral?...the roller should go beyond those marks, and the throttle plate should be slightly open when you have the throttle advanced as far it will go with the motor in neutral...then at wot in gear...the roller should be on the highest point of the cam and the throttle butterfly should be exactly horizontal in the carb throat

The idle is adjusted with the engine warm, pushing the boat in forward gear. It's a combination of idle mixture adjustment and adjusting the idle stop on the port side of the engine < tension spring and screw at rear of the tiller handle >.

At no throttle the cam roller may not even be on the cam.

To start the motor try full choke, motor in neutral, and the throttle advanced as far as it will go in neutral. After the tries to fire, kick the choke off and see if it'll start < you may have to go to 1/2 choke, depends >..when it does fire and run, reduce the engine speed and warm the motor up some before taking off.

The roller is touching the throttle timing cam.

The roller won't rest between those two lines either at full throttle or at no throttle in ANY gear.

Here is a picture of where it is at no throttle.

Here is a picture of the right side of the motor with no throttle. Is this is far back as it should go at no throttle?

Does the plate with the two lines have the ability to be moved and adjusted where it rests and that's why my roller wont hit those marks?

Thanks,
Ryan

AlTn · Oct 15, 2012

Re: 1976 Johnson 25 Stalls when given throttle

the 2 marks on the magneto plate are used in setting the points opening when using a timing fixture tool...the "notch" on the throttle control cam < just to the right of the 2 marks on the mag plate in pic 1 > is the mark to adjust the carb butterfly initial opening with...

in gear you should be able to get the mag plate to move enough so that the carb roller moves from the lowest point on the throttle control cam to the highest point on the cam

lindy46 · Oct 15, 2012

Re: 1976 Johnson 25 Stalls when given throttle

Loosen the bolts on the cam and it will move in and out. Adjust it so the throttle butterfly just starts to open when the roller hits the mark. When the throttle is wide open, the butterfly should be fully open. IGNORE the two marks on the mag plate. They have nothing to do with the "link and synch". They are for adjusting the points with a special tool.

IM Buddy8 · Oct 15, 2012

Re: 1976 Johnson 25 Stalls when given throttle

lindy46 said:
Loosen the bolts on the cam and it will move in and out. Adjust it so the throttle butterfly just starts to open when the roller hits the mark. When the throttle is wide open, the butterfly should be fully open. IGNORE the two marks on the mag plate. They have nothing to do with the "link and synch". They are for adjusting the points with a special tool.

What/where are the bolts on the cam that will let cam move in and out?

I think the link/sync is good if I ignore the two lines. For some reason I thought that was part of the throttle linkage adjustment (the double barrel clamp with flathead in middle to hold linkage stiff.)

If this is all set correctly what could be a reason why it kind of gasps for gas when I move the throttle up quickly?

Would trying it on a lake make a difference compared to testing this in a barrel?

Thanks again for your help!

AlTn · Oct 15, 2012

Re: 1976 Johnson 25 Stalls when given throttle

at marineengine.com...your year,hp,model...magneto diagram...# 26 and 27 attach the throttle control cam to the magneto plate..may require a 90 deg. straight slot to get to w/o removing the magneto plate

fireman57 · Oct 15, 2012

Re: 1976 Johnson 25 Stalls when given throttle

Sorry that I haven't been on here but did you clean your high speed when you had your carb apart? Sounds like that might cure your problem. any little bit of stuff in there will make it act up.

IM Buddy8 · Oct 17, 2012

Re: 1976 Johnson 25 Stalls when given throttle

AlTn said:
at marineengine.com...your year,hp,model...magneto diagram...# 26 and 27 attach the throttle control cam to the magneto plate..may require a 90 deg. straight slot to get to w/o removing the magneto plate

That plate that the throttle roller rolls on doesn't look adjustable. It looks like the two screws just hold it in place?

@ fireman57, I cleaned out the high speed jet, it was terribly dirty in the bottom where it gets the fuel for the high speed pickup. I think it's about 98% clean now. A couple hard black pieces of debris that didn't want to come off in there but very small and I don't think they should affect anything.

Going to try it out on the water soon. I'm also going to make sure the spark can jump 1/4" and the compression is still good and within 10% of each other.

Thanks,
Ryan

fireman57 · Oct 18, 2012

Re: 1976 Johnson 25 Stalls when given throttle

It sounds like you have a fuel line breaking down if you have hard black pieces in your carb. If you don't change it or put an inline fuel filter on it you will get the same stuff back in there. To adjust that plate you have to take the cotter pin out of the plastic piece that screws on the top of that plate and turn the plastic piece until your roller hits the marks then adjust your throttle cable and screw stop from there for your idle.

IM Buddy8 · Oct 24, 2012

Re: 1976 Johnson 25 Stalls when given throttle

Check out this video please. This is the range the throttle plate rotates from no throttle - full throttle.
Thanks,
Ryan
http://imageshack.us/clip/my-videos/547/pbekxvtuvbgqmbuwvszakk.mp4/

fireman57 · Oct 24, 2012

Re: 1976 Johnson 25 Stalls when given throttle

sorry but I can't see the vid because I am still on dialup out here in the sticks. All you need to really do is look at the side of your engine and push your throttle forward and then you can see when the butterflies on your carb is opening up. when you advance the throttle just watch your linkage, you will see it move when you get to a certain point. Also, you will see the timer base move at the same time that the linkage on your carbs move. Hope that makes sense.

IM Buddy8 · Oct 25, 2012

Re: 1976 Johnson 25 Stalls when given throttle

I'm pretty sure I know how to set what you explained. I think something is wrong somewhere if you were able to watch the video you might be able to tell me right away. If you leave the link open for about an hour to buffer will you then be able to watch it?

Thanks I appreciate your effort,
Ryan

IM Buddy8 · Nov 3, 2012

Re: 1976 Johnson 25 Stalls when given throttle

Is anyone able to watch the video above?

Thanks,
Ryan

fireman57 · Nov 3, 2012

Re: 1976 Johnson 25 Stalls when given throttle

you have a pm

1976 Johnson 25 Stalls when given throttle

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