HD 25 Carb percolting

[chacha53]

My Johnson HD 25 carb is percolating up through the gas shut off needle in the float bowl. Carb is too hot to touch after just a minute of running. Obviously overheating. I checked the water pump and it looks OK however, the rubber fitting on the end of the water tube(?) where it meets the pump is rather rough. Can that be replaced?
I don’t see water spurting from the two exhaust holes near the top of the leg, but I did see water come out of the bottom of the power head when running after I removed the head drain plug.
Also, I removed the four bolts under the cavitation plate a few inches above the gear case thinking I could drop the drive shaft and water tube with the foot. It wouldn’t pull off. A lot of gear oil leaked out at the seam. Is that normal? Should there be a gasket?
I really need a diagram of the lower workings of the HD 25 if anyone has one.
Thanks

[chacha53]

Ooops! I misspelled percolating!

[Buccaneer]

Not sure if this parts PDF will help.
I can’t remember if it was the early HD or TD Johnsons,
but there was something in the manual about gas
percolating in he carb, and the cure was to put
a piece of wire / rod in the carb somewhere to
restrict the flow.

---

Attachments:

JohnsonParts-HS.HA.HD-15.pdf

Prepare to be boarded!

[frankr]

I had one of those HD’s drive me nuts. Turned out the rubber seal at the bottom end of the water tube was obstructing the flow. It "seemed" to be fine. It is essential that the water flow be 100% or the carb will overheat and vaporize.

[chacha53]

The pdf helps. Thanks Buccaneer!
Frank, I think that may be my problem. I took a pic but now I can’t figure out how to attach to this post. Anyway,the rubber part at the bottom end of the water tube looks rough. Does it have to match up perfectly to work or can I clean it up with an exacto knife? What did you do?

[frankr]

On most of them that I’ve found, the rubber is mushed over the end of the water tube. I just trim it away. Of course the general condition of the pump is important also. Make sure the rubber rotor isn’t swollen and fits the eccentric cam properly.

[garry-in-michigan]

the rubber rotor must be an exact fit to the brass eccentric that drives it. . . 🙂

[chacha53]

It looks to me like someone tried to put a little black silicon around the rubber on the end of the tube. The rubber rotor looks ok so i just cleaned everything and tried it again. No change. I think I should put in a new rotor. anyone know of a source?

[frankr]

Two club members make them

Brian Wilcox Call 810-794-7685 before 8 pm est please.Or email Baron0418@att.net. please note the b must be a capital.

AND/OR—

http://home.earthlink.net/~flyingscott/

[chacha53]

I bought a new rubber water pump rotor (reproduction) and the engine is still overheating! I checked each end if the water tube for obstructions. There were none. I put a vacuum on the water pick up tube and it held, so the tube isn’t leaking. I removed the head and checked the water jacket for obstructions and all was clear. I installed the exact spark plugs per the old outboard book just in case the plugs I was using were too hot for the engine.
I removed the spark plugs and the drain plug at the base of the power head, then spun the engine with an electric drill with the engine in a water tank. At high speed, the water just dribbled out of the drain. I read somewhere that someone got theirs to shoot water about 5 feet with the drain plug removed and the engine running fast for just a moment.
I thought maybe my rubber rotor didn’t fit tight enough so I soaked it overnight in mineral oil. No change. There is a very small gap between the rotor and the cam that spins within it. I read somewhere that it should fit tightly on the cam. Could that be the problem?
Does anyone have a close up picture of what the bottom end of the water pick up tube should look like? I think mine may have been slightly altered wrt the black rubber fitting.
I’m about to give up!

[Author]

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