HD 25 Carb percolting

[frankr]

Soaking that rotor in oil may not have been the wisest thing to do. Oil makes them swell up. Other than that, I don’t know what the problem is with yours.

[shane-r13]

I’m having the same issue, everything seems in order except my rotor looks swollen to the eye. Ordering a new one from Brian Tomorrow. Hope I have better luck.

---

Attachments:

[chacha53]

I soaked it in mineral oil in order to swell it in hopes the cam would fi tighter without any gaps.
My water pick up looks like the rubber has been trimmed off even with the copper tube. It looks blocked in this picture.
I’d be interested in knowing if yours works with a new pump.

[shane-r13]

I have trimmed that piece of rubber at the end that looked rough. Hope it does not have an adverse effect. I’ll find out I guess. Should the pump be a tight fit on the outer rim as well as around the cam? Or just on the cam and loose on the outer area?

[garry-in-michigan]

ABSOLUTELY NOT ! – It should be a tight fit on the center eccentric cam only. The gap on the outside is for the water. No gap, no water. . . 😎

[chacha53]

I think trimming is a mistake. I did that to mine and now I can’t’ get more than a trickle. I found the HD25 parts list and there is a seal listed for the lower end of the water tube. I think that is what I trimmed off. Not sure what to do now. Maybe I could build a seal using black RTV to look like yours.

---

Attachments:

[aquasonic]

In my experience, even when set up correctly, the HD-25 is a very hot running motor. The integral exhaust/intake/carburetor design is prone to overheating the fuel in the carburetor. Once the carburetor/exhaust/intake get too hot, the fuel can and will boil in the carburetor making it impossible to start the motor until it cools down enough to run again. They can, however, be serviceable motors.

Remember that these motors are around 70 years old, and that means that the water pump AND the water tube seal should be replaced. I own a 1947 HD-25 that cooled fine the first time I ran it, then overheated quickly the next time it ran. After giving me fits, it turned out that the water tube seal/grommet had swelled up from exposure to water. The tiny, maybe 3/16" opening, was closed up significantly, choking off the water supply causing overheating.

Back to the original post, there is a gasket between the gearcase and the midsection that separates water from the gear oil. If you separate the two, then you really need to reseal that gasket, or better yet buy or make one. That is a very important gasket.

Here is a picture of the water tube seal/grommet:

[chacha53]

Great info! Where can I get a replacement grommet?

[shane-r13]

quote Garry in Tampa:

ABSOLUTELY NOT ! – It should be a tight fit on the center eccentric cam only. The gap on the outside is for the water. No gap, no water. . . 😎

Thanks for the diagram Garry. I’ll be sure to refer to it when my new pump rotor comes in.

[aquasonic]

quote Chacha53:

Great info! Where can I get a replacement grommet?

Best to post an add on our Free Classifieds Section of this website. Members have parts to sell. If no luck, then you can "pay up" for the part.

http://www.marineengine.com/newparts/pa … OMC0300582

https://www.ebay.com/itm/OMC-EVINRUDE-J … itleDesc=0

[Author]

Posts