Johnson 25HP issue

[jonmac3569]

Run the engine again after pumping up the primer bulb and visually check the pump output flow. You may have to do this at higher RPMs to really check it and you wont have much time before the bowl runs out of fuel. At least verify operation at idle.

Thanks, I'll try that

 

[jonmac3569]

Well I just put on a brand new OMC fuel pump. I put it on and took it out to try out. Exact same thing! No difference whatsoever. Any ideas?

 

[crazymanme2]

These are some pics of an exploded view of your fuel pump. :lol:

 

[jonmac3569]

Thanks but I replaced it with an out of the box, already put together, pump. The frist time I rebuilt it, but today I replaced it with a new one.

 

[jonmac3569]

I am a little worried about the gasket being wet on the carb. Maybe air and fuel are seeping out there. I initially used a non-omc rebuild kit so I ordered an OMC kit and I am going to rebuild the carb again and check the jets and valves again just to make sure. Hopefully that will fix the issue.

 

[mmf]

sounds like you might be running on one cylinder. Run motor at idle in a barrel and pull one plug at a time to see if it makes a difference. You have a lot of unburned fuel coming out, this is usually found when there is a bad coil or other ignition problem making a cylinder NOT fire.

 

[jonmac3569]

Thanks, I'll try that!

 

[user 6672]

You can also check to see if they are both firing by hooking up an inductive timing light one at a time.. while running the light will flash.. if you have a dead spot the light will go black etc..

 

[jonmac3569]

Great news, today I finally had a chance to take it out. I recently took the carb back apart and cleaned all the jets, etc. i also rebuilt it with an OMC kit this time. Not sure which was the problem (or both) but it runs great now. Thanks for the help.

 

[jonmac3569]

Took the motor out the other day and it was acting funny. Ran great the previous time I took it out. I adjusted the cam follower since then because the throttle was not opening at the correct point. (per the serivce manual) I apparently did not adjust it correctly, I took it out again and although motor was running well, I could not get past a low throttle setting. I could phyiscally move the throttle to the "fast position" but not getting much out of it. I re-adujusted the cam follower on the fly. After that I could open the throttle up and it seemed pretty normal. Only thing I did notice is that if i opened the throttle up to WOT it would "slip" or sounded like it was kicking out of gear. I am pretty sure that i still need to get the cam follower adjusted correctly but does anyone know why it is kicking out of gear at WOT?

 

[cajuncook1]

Unfortunately, it may a good possibility that you have a worn clutch dog and or forward gear. Not cheap. I hope I am wrong.


Part numbers 31 (clutch dog) and 33 (forward gear)

Another possibility, you may have gotten some trash in your high speed jet causing lean condition.


Another possibility, you may have a coil going bad that is intermittently missing (not firing). Check the coils for apparently cracking. Bad coils can start missing when the engine warm ups.


I would check the coils first. It is your cheapest and easiest option at this point.

Here is a You Tube link on how to check your coils with multimeter. Can get a multimeter cheap at radio shack or similar store. They show how to test an OMC coil.

https://www.youtube.com/watch?v=KT8rk5QWgS0

 

[cajuncook1]

If your clutch dog is worn, then you maybe able to flip the clutch dog around. The teeth on that end infrequently com in contact with the reverse gear, so are usually not worn on that side. Most usually don't use the reverse gear much and certainly not at high speeds.

I would still investigate your coils to make very sure.

 

[jonmac3569]

Thanks for the posts. It is also fouling plugs. I pulled them earlier and that is the 2nd set it has fouled in a short time period. I will check the coils. I was planning on taking it out tomorrow, is it going to hurt anything to run it more? Would probably only be for a short time since I will be going up river to hunt a short distance, could always float back down with trolling motor.

 

[jonmac3569]

Checked the coils (based on the video) they are both good. I am guessing you are right about the gear or clutch dog. It felt like a transmission slipping or something like that, not a loss of power, the motor was still "revving up" but the prop was not turning.

 

[cajuncook1]

If your plugs are fouling up then there are couple of reasons:

- Too rich of a low speed setting

- If you are doing a lot of low speed trolling with your motor and you don't have the proper spark plugs. If you are going to do a lot low speed trolling for extended periods of time then you will need hotter plugs.

- You are intermittently or consistently running on one cylinder and thus the build up of oil/carbon on the plugs

- If your thermostat is not functioning properly or you have no thermostat. Thermostat usually fault in the open position, but not always.

If you have no thermostat (or faulty) to maintain a powerhead running temp between 130 to 160, then the cold waters that you are running your motor in will accelerate the carbon/coking build up process in your powerhead, on top of your cylinders and around the rings. Your plugs will foul up in no time causing the problems that you are having now.

The thermostat stays closed until the temperature of the powerhead starts reaching about 130 to140F, then the thermostats starts to open to allow some water in to circulate around the water jackets to cool off the power head to maintain a good operation, again between 130 to 160F. So, the thermostat will open and close to help maintain operation temperature. It is within the 130 to 160F range that the optimal combustion of the fuel oil mix takes place.

If you have no thermostat in or it is faulty then water will circulate around the water jackets all the time and the powerhead will stay much colder. Colder powerhead temperatures will allow the unburned fuel oil mix to build up and slug up all over instead of being burned off or exiting the exhaust/water mix going out near the foot of the motor.

Things to do

1. check your thermostat
2. gap your Champion J6C plugs to 0.030 (hotter and better plug for trolling)


If your plugs are fouling, then they can't spark properly and may create poor running conditions.


Some things to think about.


***Another thing that came to mind, if your motor is revving at higher speeds, but the propeller is not turning, then your prop hub may be slipping. (The prop hub is harden rubber material in the propeller that allows the prop to spin but if it hits something hard, then it will break and slip to protect the gearcase and drivshaft and motor from damage.

Read this link, it will tell you how to diagnosis a spun hub.

https://www.tinboats.net/forum/viewtopic.php?f=4&t=13786

 

[jonmac3569]

Thanks for the info. I will try that.

Took it out today and it ran pretty good other than doing the same thing. Ran good up to WOT then motor would rev up and at the same time prop would stop spinning or slip out of gear? Not sure which but I have some stuff I can try now.

At least I have until spring to get it figured out.

 

[jonmac3569]

Checked the thermosat, definatley failed in the open position so that explains one of the issues.

 

[jonmac3569]

I am changing out my thermostat today. The old one was failed open. I found this rubber plug (see pic) in the hole that was just beneath it. It was not in one of the bolt holes, there are 3 of those. it does not say anything about it in the service manual and does not show it in the parts list. Is this supposed to be here? what is the purpose?

 

[jonmac3569]

Here's a better pic of the plug that was in there. It appears to be manufactured, not something that melted in there. It has a taper on the bottom and a ring around the top which doesnt match the tube I pulled it from. It fits snug in there but the taper doesnt reach the bottom of the port. (scratches along the top are from me prying it out) Is this something that may have been added to change the performance in some way? run hotter? etc

 

[crazymanme2]

Looks like some sort of water by pass restrictor :?: