Johnson 15 hp motor die's on full throttle

[arctic_dan]

Ok sounds good. The main jet was taken off and cleaned as well as the main passage to the inside of the carb. The Needle clip you are speaking about is there yes and works freely. When i blow in the intake fuel passage it lets air in when its right side up and when its upside down it seals properly.
Ive take apart my pump again and went through the step by step instructions on the link you sent me. Tho I dont think I had anything wrong we will see when I take the boat back out to see.
Also looking through the manual you sent me. I do have the slow speed needle. But I do not have a high speed needle. I only have a main jet.

 

[arctic_dan]

Did a compression test. We have 120 psi on both sides.

 

[oldboat1]

50:1 oil ratio. Check the temp after running a bit (should be able to hold your hand on the top of the head for a few seconds). Also consider use of a timing light to see if you are dropping a cylinder at higher rpms, as described above.

 

[arctic_dan]

I have the correct mix ratio. The temps are normal also. I will need test with a timing light I suppose. What size main jet should be on it?

 

[arctic_dan]

Reposted by accident.

 

[oldboat1]

http://www.iboats.com/Carburetor-Ma...354719--session_id.962938471--view_id.1537182

.056 (orifice number 56: pn 0326858)

 

[arctic_dan]

Your right, I have the 56 main jet in there. Took the carb apart again to check it out.

https://www.dropbox.com/s/h2x9rcktchydevo/DSCN2947.JPG?dl=0
https://www.dropbox.com/s/1kf6dzj334lmb3o/DSCN2948.JPG?dl=0

 

[oldboat1]

Make sure the float isn't upside down (looks right in the pic -- tab appears to be correctly aimed toward the needle seat, can't see it anyway).

The h.s. orifice has to be undamaged -- in the pic looks like it may be a little out of round, but maybe a shadow. Folks damage them trying to ream them out.

That timing light would clamp onto a wire, and lay somewhere with the flash visible. No flash means no spark. (I have the old fashioned type that hooks to the battery, but you might have the self-contained type, or get your hands on one -- not a big expense.)

 

[arctic_dan]

Yea. Ill have to get me a timing light to check that out but again in theory it wouldn't make sense that its electrical cause the motor runs good when I put the choke on. Would it be because the spark isnt hot enough to ignite the fuel/air mixture? Then again adding more fuel makes it harder to ignite. Im currently shopping for a timing light. Even tho it doesn't make sense to me I'm willing to try it.

 

[oldboat1]

Compression, spark and fuel. Compression tested good. Spark needs to be tested: measured with open air, adjustable tester. Look for a sharp half inch. The timing light helps to determine if a cylinder is dropping out (not getting fire) at higher rpms.

 

[JJsays77]

Make sure the float isn't upside down (looks right in the pic -- tab appears to be correctly aimed toward the needle seat, can't see it anyway).

The h.s. orifice has to be undamaged -- in the pic looks like it may be a little out of round, but maybe a shadow. Folks damage them trying to ream them out.

That timing light would clamp onto a wire, and lay somewhere with the flash visible. No flash means no spark. (I have the old fashioned type that hooks to the battery, but you might have the self-contained type, or get your hands on one -- not a big expense.)

Thanks!! According the schematic of my carburetor you're right! My float was upside down! The dumbo I bought it from had it upside down so I put the kit back in the way I saw it. Still have to take it to the lake to check it out, but I have a good feeling because, well, it was upside down.

So you might want to double check that float there Arctic Dan!!

 

[JJsays77]

Thanks!! According the schematic of my carburetor you're right! My float was upside down! The dumbo I bought it from had it upside down so I put the kit back in the way I saw it. Still have to take it to the lake to check it out, but I have a good feeling because, well, it was upside down.

So you might want to double check that float there Arctic Dan!!

Well good news and bad news. I took the boat out today and she went full throttle for a few seconds then bogged. I couldn't even get the throttle barely open before so much improvement! But, in order to get the motor staying at full throttle I need to pull the choke a little bit. There's something we're still missing Dan and it's giving me grey hairs! Haha

 

[tomhath]

...But, in order to get the motor staying at full throttle I need to pull the choke a little bit. There's something we're still missing Dan and it's giving me grey hairs! Haha

Sounds like fuel isn't getting to the carb. Could be a weak fuel pump or air leak in the fuel lines.

Now that you have it running better try pumping the bulb again before it has a chance to bog down.

 

[Crosbyman]

if it went full throttle for a while it did suck the gas and enough air from the carb face to work
.
now the starving part at wot ....

cut the starving problem in half....

​hook up a small supply of gas above the carb and hose it down to the carb inlet ( feed it gas by simple gravity) if it runs WOT the problem is in the fuel pump or tank side of the motor

​ if it does not run by gravity feeding fuel to it................ the problem is in the carb inlet to h/s channel feeding gas to the carb throat


...electrical issues aside of course

 

[JJsays77]

Sounds like fuel isn't getting to the carb. Could be a weak fuel pump or air leak in the fuel lines.

Now that you have it running better try pumping the bulb again before it has a chance to bog down.

You might be on to something! While I was at the lake I did try priming the bulb but that didn't help. I noticed though that it wasn't getting hard and felt like some air was in it. It's weird though because I did replace the tank to motor lines/bulb, to and from tank to pump to carb lines, and the fuel pump itself. The first fuel pump replacement I bought wouldn't even pump. Weird right? Then the second new one I installed does pump but it doesn't seem like much it's doing a great job. They aren't installed upside down either.

Also, while I was at the lake yesterday I ran some seafoam through the motor. When I was done with that I switched the line back to the actual tank. I noticed it was difficult to prime again. I had to shake the bulb while I was priming to get it to start priming again. Could air have been trapped in the lines? Is there a way for the air to escape while priming?

Lastly, when I did change the line from the pump to the carb I went a size up from the 5/32 to a 3/16" because 5/32 is impossible to find. Could this be an issue?

if it went full throttle for a while it did suck the gas and enough air from the carb face to work
.
now the starving part at wot ....

cut the starving problem in half....

​hook up a small supply of gas above the carb and hose it down to the carb inlet ( feed it gas by simple gravity) if it runs WOT the problem is in the fuel pump or tank side of the motor

​ if it does not run by gravity feeding fuel to it................ the problem is in the carb inlet to h/s channel feeding gas to the carb throat


...electrical issues aside of course

Ok that's a great way to troubleshoot, thanks! I have a small tank to do this with but I'm trying to figure out a way I can feed it with gravity though.. hmmmm

 

[arctic_dan]

jjthejetplane773 Im happy to see your still at it. This problem is making me pull out my hair also. I had posted a couple pics on my post. You can see that my float is right side up. I dont think I can put it upside down due to that groove on the one side that will only fit one way.

Im waiting for my timing light from amazon so I can test that.
oldboat1 Spark tested. Nice and strong at 1/2 inch and beyond. Motor never missed a beat. It runs great which is upsetting that it is giving me this issue. Im waiting for my timing light I purchased from amazon now. I also went out and bought new plugs and I will replace them on the water to see if there is any difference. I will report back when I get more info. Thanks for the help. "if" I ever find the problem I will let you know. Keep in touch and let me know what you can find.

 

[arctic_dan]

reposted again by accident

 

[Crosbyman]

Ok that's a great way to troubleshoot, thanks! I have a small tank to do this with but I'm trying to figure out a way I can feed it with gravity though.. hmmmm

---

• just hold it a few inches above the motor.... you don't need much ... a cup or two

 

[arctic_dan]

So took it out to the lake today and the motor is still surging at WOT until i pull the choke. I also put new plugs in on the lake with no difference. Whats upsetting is that the motor runs great on bottom end. When you troll it keeps a nice pace.
https://www.dropbox.com/s/htwo970ayt...32-22.3gp?dl=0
I started playing with the low speed needle and it seemed to have helped my cause when I would richen the mixture. I was at a point where I was almost 2 + turns out and it would start to run nice but when I would go back to idle the motor it wouldnt cause it was flooding. They say the low speed needle doesnt affect top end but it does to an extent. Im running out of idea's.

 

[Crosbyman]

you keep chasing the same issue ...:deadhorse: it starves at H/S :faint2:

low speed and high speed delivered gas by two separate routes (drip chamber on top for low speed
​and HS jet for high speed.

​it is having a hard time sucking gas ...with outside air at high speed

I don't have a 15hp carb in hand but check all passage ways you may find one going... nowhere but is essential to allow air in the float chamber
it must not be plugged .... with the full floating and inlet blocking entry of new gas and the chamber not venting" in".the carb body..... the high speed circuit is depressurizing and doesn't allow anymore gas to exit the H/S route nthego:


​ that is the theory for today anyway...:lalala:

​ make 100% certain you can blow each passage way clear with carb cleaner check the carb body for airline cracks