4hp Johnson Deluxe stalls out.

[loworange88]

Hey everyone. I have a 1992 Johnson 4Hp Deluxe twin outboard. I got the motor used from a coworker. The engine did not really run when I got it, I had to remove the carb and give it a basic cleaning and put it back together. Also the water pump impeller was beat, so I changed that, and gave the bottom end a fresh fill of fluid. OK, so I can get the engine running if its cold(maybe 4-6 pulls), it will idle decent enough. So when I engage it into gear and travel across the water I can go about 300 yards(ish) and then the pitch of the engine changes, it sounds as if its under heavy load, then it usually bogs right down and stalls. The cylinder head where the spark plugs are seems to get hot, and I get a little bit of grey smoke under the cowl, but once I open it I cannot tell where it comes from. Restart at this point is super hard, if at all. After it sets for a while, it will start up again( usually alot of pulls) it will stumble 3-4 times before it actually stays running. So then all over again, it will run strong for a short distance and then peter out and die.

I was trying to keep sqeezing the primer bulb incase I was losing fuel pressure, but that didnt seem to make a difference.

I was suspect of the ignition coils, so I tested them with my meter, and one was 252, and the other was 260. My manual stated 275 +/- 50Ohms.

I was suspect of the safety kill switch at one point so I disconnected that via the factory single pin plug. I did test the continuity of the circuit and it checked out as "good" per the manual.

Lastly I have taken apart the fuel pump which seemed to be in decent shape, but I ordered a new gasket kit for it anyways and that is currently in route. What other items should I check or attempt at this point.

Thanks in advance.

 

[GYPSY400]

I would recheck the carb for proper float level and check your needle and seat for proper fuel flow.

Sent from my SM-G903W using Tapatalk

 

[maintenanceguy]

Three guesses:

(1) Fuel pump is shot. When you squeeze the primer bulb, you fill the carburetor's float bowl with gas and it runs on that gas for a short while. Since the fuel pump hasn't re-filled the float bowl, you're carbs run out of gas. It slows down a sputters for a few seconds as the carb pulls the last tiny bit of gas mixed with some air and then it dies. But...it doesn't make sense that it won't start right back up again. If you squeeze the primer bulb until it's firm, it should be good to go immediately.

(2) The float needle or float is not working properly and won't let in the proper amount of fuel. Same situation as above, carb runs dry and motor dies.

(3) No cooling water - overheating. Impeller may be new but it's still not pumping water. If your old outboard has a telltale, you will know if it's working. But, if it doesn't have one, water flow is a guess. Maybe a tube is plugged, debris from old impeller is somewhere blocking something, the pump housing is damaged, the impeller is loose on the drive shaft, the cooling passages in the engine are plugged with corrosion and salt deposits, or something else is making it not pump water. The motor runs until it's too hot and you will hear it speed up a little as the engine gets hotter.

Eventually, the engine gets so hot that the fuel ignites as soon as it hits the cylinder head - too early for the engine to run. It cools down and starts several minutes later.

 

[loworange88]

Thanks for the responses.

Like I said I ordered a fuel pump rebuild kit, and for good measure I just ordered new coils. As far as the water flow, this model doesn’t have the typical “pee hole”, according to the flow diagram in the repair manual, it pushes the hot water back down the shaft housing while a little bit spits out the exhaust holes. What’s a good way to check that the path is clear, short of tearing the whole top end apart? Compressed air? There are no removable plugs that I can easily see.

 

[Pappy]

Sounds to me like the engine is seizing.
You may have missed the tube when re-assembling the gearcase to the exhaust housing.
Hopefully you are running at least a mixture of 50:1 in it?
Look for signs of overheat. Discolored paint on the cylinder head. Same on the exhaust cover.
Take a temp gun and shoot the top of the cylinder head at idle after it has been running for several minutes.
Should be around 135f. No temp gun? Hold the palm of your hand against the top of the cylinder head. Should be able to hold it there for 5-6 seconds. Be careful. If the engine is overheating you may get burned.
If you think you are running on the thermostat at idle then take it for a short run with the cowling off. Touch the top of the cylinder head. It should be running noticeably cooler than at idle. If hot then you have probably been seizing the engine. A compression check will be necessary to see what damage has occured at this point.
Classic symptoms of an engine that is seizing is that it feels like something is putting the brakes on the flywheel at WOT and physically stopping the engine. The engine may smoke or the flywheel may be completely seized. After a few minutes the pistons will cool and unstick or unseize and sometimes the engine can be restarted. Usually the idle will not be as good as it used to be. If these symptoms match what you are experiencing then the little engine may have damage already as you have "stuck" or seized the engine several times.
Sure hope it is simpler but you describe classic seizing.

 

[loworange88]

Ok, so I did some digging....I dropped the lower gear case, and the water tube did not seat correctly, so theres that.

I did a compression test, and the max I got out of the top cylinder(1) was 45 lbs, and the lower cylinder(2) was barely 30. So I pulled off the cylinder head and sure enough the head gasket was blown out on the bottom right. I scraped off the gasket and did a quick check with my Starret square blade, and the case, and the head cover seem to still be flat, but yes there is some discoloration on the head cover.

So what is my next course of action? This is just outside my normal box, of repairs. Not sure if I can just put a new gasket on and reassemble, or do I have to get further into it? Do the cylinder walls need to be dressed? Perhaps piston rings? The flywheel turns easily by hand, and I dont see any drag, or "rough areas" through the range of motion.

 

[nccatfisher]

How do the cylinder walls look? No scratches, gouges etc? Visible score line?

 

[loworange88]

The cylinder walls feel ok. My neighbor was just over and I asked him what he thought. He said same, they look ok and they are smooth to the naked finger. There is what looks like a score line, but if it is, its smooth to the touch, I ran my fingers all around both cylinder walls, and I did not find anything that jumped out at me.

 

[Pappy]

Sorry to break the news to you but those cylinders are anything but normal. The score marks are there and I see lots of them. Also note the difference in piston color around the ports.
Read again (above) where I told you that after sitting a few minutes the rotating parts will unstick and you can once again start the engine. Once the engine starts it will cut and smooth the bores which is what you and your neighbor are feeling. Double the oil mixture for a while and the little engine may get through this. Check your water pump impeller and the cup to see if there is damage there.
EDIT - On a 2-stroke if you go the distance the bores will have to be honed at the bare minimum. This is assuming the bores are still within specs.Pistons should be changed. See those light colored vertical stripes? Those are aluminum transfer areas. Yes, the aluminum comes from the piston. To do this correctly the engine should be overbored and new pistons and rings. For you the easy way may be to source a good used powerhead and install. But let's go the simple route right now. Install a fresh new head gasket. Check compression again. Run double oil (24:1) for a few gallons of gas and lets see how the engine responds. I know the magic number for bare minimum compression but I want you to tell me what you get.

 

[Sinkingfast]

Bought a sick mercury 4hp that was inhaling aluminum powder from the recoil pulley shredding itself. Ran 20-1 for a couple gallons and it came right back...I run 20-1 normally anyway so no big deal. It just might work..

 

[loworange88]

Pappy, thanks for the insight, like i said once inside an engine I’m a little out of my element.

I ordered a new head gasket and I will proceed with re-assembly and I’ll do a compression test and a leak down test at that point.

Thanks for the tip on the double oil, I didn’t think of that, and it makes sense to try.

Stay tuned, I’ll update when I get it back together.

 

[nccatfisher]

Pappy got to you before I did and has forgotten more than I know but he is correct about that bore. He also knows way more than I do about reviving old motors, I wouldn't have thought about the double oil and trying to see if it was salvageable. I would have went into recovery mode before you did more damage to it.

 

[Pappy]

The reason why I suggested a double oil regimen is because it is a 4hp engine. Had the engine been a larger more powerful engine I would have gone the rebuild route.
The engine is already damaged and chances are the aluminum has the rings stuck in their grooves but lets see if it will come back some and provide a decent service life.
The 4 Deluxe is a very nice engine, well worth saving and is a nice running engine as well. Should he decide to do it right there are .030 oversized pistons and rings to do it with.

 

[loworange88]

Ok. Parts came and I reassembled the motor. The compression seemed to top out at 75ish on both cylinders...it’s been running for about 10 minutes and sounds pretty good. A little Smokey due to the additional oil. So far so good. Water is coming out the pee hole pretty steadily. I can hold my fingers in the exhaust cover and it’s not burning me.

 

[Pappy]

That carb should have the adjustable low speed in it. Lean it out some at idle until the idle smooths. A bit too far and it should pop lean. Thats okay just richen between 1/8 and 1/4 turn or so and get it back in the sweet spot.
I have not seen a cylinder head that badly overheated in a long time!!! That thing is toasty brown! The paint is what produced the smoke for you and what you were probably smelling.
75psi is bare minimum I would consider. Continue to run it easy for a while. Go troll some plugs for an afternoon or something. Check and see if the compression comes up. Am fairly sure you have stuck rings at this point but let's let it run and see what they do.
I would check the thermostat and see if it is still working. The top of the cylinder head should be around 130-135F at idle. Your checks should be made there. Palm of your hand should be able to stay there for 5-6 seconds before you give up and pull away. Should cool as the engine is brought up in the RPM/Power band,