Changing water impeller on 49DS etc Yanmar 4JH

[artboas]

It is well known that changing the impeller on the Yanmar 4JH is a huge problem, in that the pump faces backwards, and is under the alternator.
I have developed a fix for this, and it will permit you to change the impeller in about 15 minutes with no problems.
It’s all posted on the Hunters Owners site on the Big Boats forum.

Best of luck!!

[Zanshin]

I recall having spent a lot of time changing impellers on my 49DS.

Could you put the post here or put an actual link to the article in this thread?

[panoramix]

I googled, and found the forum which has the following suggestion:

>>>>>>>>>>>>>>>>>>>
You can buy what are called crankshaft mounted water pumps.
They basically bolt onto the front of the flywheel, and you have a small stabilizer arm to keep the pump from rotating. I'll need to make a small adapter plate for the flywheel out of aluminum . No biggie.
The the hoses will provide enough static friction, but the arm is a good idea.
These pumps are rated up to 5000 rpm.
Cost approx $200.
<<<<<<<<<<<<<<<<<<<

So forget the original pump and re-route the hoses to the new pump on the front.

Google on "crankshaft mounted water pump"

[artboas]

I have an extensive document on the upgrade.
I haven’t found a way to post it into this site
So, if interested please email me

Thanks

[Bijoux]

Posting Document:

PDF for Build and Install


www.23hq.com/Bijoux22/photo/62017033/original

[artboas]

Just want to thank my new friend for assisting with posting this document to the site.
As you will note, the instructions are quite thorough, and pertain to my Hunter 49, although the solution is very similar for the J49DS
There is one thing that requires modification from the documentation; that being the method to install an anti-rotation bar which attaches to the pump body.
My final installation varied from the documentation, in that the anti-rotation clamp needs to have compliance to accommodate the motor moving around on its mounts.
My final solution was a stiff compression spring, integrated with threaded studs at each end. The spring gave the pump all the movement it needed to allow for engine vibration, but kept the pump from rotating perfectly.
Good luck!