Johnson 25HP 1999 Help needed on next steps to get old engine started

[jdhogan]

Model J25EEED. This motor hasn't been run in 4 or 5 years and I want to get it going. I am not the original owner. I am not that familiar with boat motors but I have time and tools so I am willing to try almost anything. Boat was always run in salt water.



So far I have:
- put in new sparks plugs
- unfrozen the starter
- cleaned and rebuilt the carburetor
- cleaned the fuel filter
- using fresh gas
- put a new connector to the engine side on the gas line (6 gallon tank). The o-ring was old and worn.
- put on a new squeeze bulb. It was cracking.
- cleaned some rust on the flywheel and the bolts with wire brush
- lubricating moving parts

This forum has been a tremendous help as I learn how to do some of these things.

The starter works great and after cleaning the carb, I was able to get it to run in idle in a garbage pail filled with water. Water spits out in a steady stream. It ran for about 5 minutes and then quit. When I adjust the carb (turning it in 1/8 turns and waiting), nothing seems to change. Still smokes quite a bit, especially when I would give it some gas and it will cough once in a while, but not constantly. Also got a thin layer of oil on the top of the water in the garbage pail. The cylinder cover in the back of the motor got up to about 165 degrees, on the side into the 140's and the exhaust cover about 120. I am concerned that the thermostat isn't working anymore or is salt-encrusted and may need to be replaced. Also concerned that air might be getting into the fuel system. Not sure how to check that. I also see a little fuel in the carb opening (very little, but not enough to drip).

I plan on changing the lower gear oil, may need to rebuild or replace the fuel filter and want to replace the water pump/impeller.

Any other suggestions? Or is it too far gone?
Thanks.

 

[Bosunsmate]

Yes check thermostat. Actually drop the whole LU and get it running without all that stuff first. You can run it for a little while like 30 secs before itl get too hot and you can check with your gun anyway. That way you rule out LU problems and water getting in where it shouldnt.
Do a spark test and also a drop test (remove a spark plug wire with insulated pliers when running) to test both cylinders are taking up a load evenly
If you can check compression thatd be good. Even rotating the flywheel by hand and feeling when the compression stroke comes on is useful

 

[jdhogan]

Thanks. I hope to get back to the boat this week after the rain stops. A little nervous about dropping the LU and running with no water. I have rotated the flywheel and feel the compression strokes, and will see if I can borrow a compression tester. I will post updates.

 

[jdhogan]

Update.
I was able to replace the thermostat and only one bolt was a problem, Fortunately it was at the top and I was able to drill it out and replace the thermostat and gasket. Spark test was good, still have to do the drop test and I am a little nervous to run the engine without the lower unit on as suggested.
My next goal was to replace the water pump and impeller. Everything came apart successfully, but when I spin the propeller shaft, the prop doesn't spin. Shouldn't it? How can I tell if the prop shaft is properly engaged? I haven't changed the lower unit oil, but it is black. I am nervous that I did something wrong when I took it apart. Also the prop shaft doesn't slide all the way down. It seems to pop back up if I push it down. I have not put the new impeller and pump on yet.
thanks.

 

[flyingscott]

Does the lower unit shift when you push/pull on the small rod? The prop shaft will not move if it is in neutral. Did you unscrew the small rod to far? Did you take out the phillips head screw in the lower unit? If nothing changes when you turn the low speed screw on the carb , you need to re visit that work also.

 

[racerone]

Did you have the driveshaft right out of the lower unit ?----If that is a yes then open the vent screw when installing the driveshaft.----It will then stay down.----

 

[jdhogan]

Thanks for the responses. I realized after I put everything back together that i needed to put it in gear to have the prop move. Sorry. I couldn't get the shift rod to move when the lower unit was off. not much to grab on to move it.
I drained and refilled the lower unit afterward. I thought a lot more oil would come out, but when I refilled it, it only took about 9 ounces. It is not in the water so I haven't tested it yet. I plan on replacing the fuel pump tomorrow or Friday and then plan to test it either in the water or in a garbage pail.
Will keep updating as I know I will need more help.
Should I replace all the fuel lines too? There is the bigger one from the fuel supply to the fuel pump and a couple of smaller ones into the carb.

 

[Bosunsmate]

If the fuel lines look at all perished then its a good idea as if bits inside get loose they will block up a carb. I put the plastic clear fuel lines on mine rather than the matty typical black ones.
To fill a gearbox it always has to be done from the bottom otherwise you will get air bubbles and it will seem full well before it actually is

 

[jdhogan]

Thanks.
I am going to replace the fuel line. It looked pretty bad and there was a slice in it, not leaking but may have been letting air in. Any trick to getting the fuel line off the connector? or removing the connector? Do I need to remove the battery cables to the solenoid to access it? It is tucked way under and the line is zip tied onto the back of the connector.

P.S. I did fill the gearbox from the bottom with a pump until it came out the top vent screw.

 

[jdhogan]

Never mind, I figured it out. Once I took off the battery cables I could see the bolt on the front side holding the connector in place. All good!

 

[jdhogan]

So today I started the engine in a garbage pail of water. It would only run for about 3 minutes at most before dying. More often it ran for about 30 seconds and seems starved for fuel. I think plenty of fuel is getting into the carb because when I unscrew the bolt at the bottom of the carb, plenty of fuel comes out. The needle is 1 3/4 turns out.
Should I remove the carb again and clean it out and check the float? Last time I replaced everything but the welch plugs. I may need to remove those and clean underneath.
Any other suggestions?

 

[Bosunsmate]

Try priming the fuel bulb when it starts running out. If that works then its a fuel issue.
Often when a motor heats up and then stops its an electrical issue so you should spark test when it stops, you can then track down if spark has failed on one or both cylinders

 

[jdhogan]

I will try that today. Thanks. Also, when I had it running, I would rev the motor ( just a little) and it would rev up, but then slow down even though the throttle was still opened up.

 

[racerone]

Test run with another tank and hose.----And another novice mistake is not enough water in a test bucket.------Fact----Water should be 8" above the PUMP impeller for best results !----Just covering the intake screen is not good enough.

 

[Rubixone]

Let me suggest something google how two strokes work, a gif to see how they scavenge exhaust at lower rpms, really neat. they will get a little hotter from water ingestion at the exhaust baffle gaskets or the base gasket, you can see this by sticking a bore scope camera in the spark plug hole, and carbon will be missing off the piston in a half moon shape portion by the exhaust ports. The water steams it off after seeing all the work you’ve done and seeing you’re still persistent problem, it sounds like this we call it washing. Been a marine mechanic 13 years this is my 14gh summer, I see this about 200 time a summer.

 

[jdhogan]

I will see if I can borrow another tank and hose. The water is probably 5-6 inches over the intake. I will add more when I try to start again.

 

[racerone]

Water has to be about 8" above the pump for safe bucket testing !!---That would be about 15" above the intake screen !

 

[Bosunsmate]

I will see if I can borrow another tank and hose. The water is probably 5-6 inches over the intake. I will add more when I try to start again.

The reason why it has to be high is because when you arent moving the boat no water is being pushed up to the pump. When you are travelling fast and the boat moves up out of the water to the cavitation plate height its fine as the speed is forcing water up to the pump.

 

[jdhogan]

I filled the pail with water, but no change. It started, lasted about a minute and died. Would only run sporadically. I decided to take the carb off again and it was filthy. Lots of gunk and I had just cleaned it a few weeks ago. It is soaking now. I am going to replace the rest of the fuel line hoses just to and try again tomorrow with a clean carb. It was fresh gas with some Stabil in it.
Can I bypass the schrader valve when I do this? I am in coastal NC, with few freezes in the winter.
Rubixone, sorry I missed your post yesterday. Do you mean that it is a hopeless case?

 

[oldboat1]

sounds like the tank might be an issue. Test the fuel for contaminants and water before running it through a clean carb. BTW, take off the welsh plug and soak the idle circuit under there.