I do mine by brail.
Are you using threaded impellers? These make a huge difference:
The above tool is used for installation and removal.
I have a little tool kit just for this job. It includes a nut-driver to remove the cover and a wrench for the impeller tool and the impeller tool.
Being left handed is an advantage.
When installing the impeller, use lots of dishwashing detergent to coat the blades. This lube allows it to go in smoothly. No need to worry about the orientation of the blades. It’ll correct itself on the first revolution. And, when you start the engine and see soapy water outside of the boat you know it is working.
I leave a blue shop paper-towel under the raw water pump for the first few minutes the engine is running to check for any leaks.
Before I started using this tool I removed the components on that side of the engine. It is only few bolts and a couple of hoses. This made access to the pump very easy from the top. However, it made the job longer and cut into my beer time. Now I can change the impeller in about 15-20 minutes (if I don’t drop anything).
Hope this helps.
With best regards,
Sailing Vessel - Cream Puff - SM2K - #275
Currently cruising - Tahiti, French Polynesia
I know a few SMo have repowered with the Yanmar 4JH4HTE. The raw water pump is on the aft/starboard side next to the fuel tank. It's almost impossible for me to change the impeller without removing hoses and alternator, and even then it's hours of struggling and cussing before it's done.
I'm writing to ask others if they are having the same problem, and how they deal with it. I'm considering removing that impeller and putting in a remote raw water pump. Previously mechanics have discouraged me from doing that, but I'm at wits end.
Any advice, thoughts, etc are greatly appreciated.