Well on the older outdrives it's inside the lower unit. I have never done one, but I have been told it takes about a Saturday, if you know what your doing. The newer Merc outdrives have the pump in the engine compartment and it runs off of the belt. I have been told they are much easier to replace.
Here is my story, I have 350 mags with alpha 1 drives. I replaced my water impellers for the 1st time at 280 hrs (They were 11 yrs old). they showed very little wear. The mechanics said I could have gotten a few more years out of them. The only reason I replaced them was for a piece of mind. I just tuned up the motors for the 1st time at 300 hrs. (12 years old). The plugs were due. Prior to the tune up & replacement of the impellers everything ran great. I was told one way to check if the impellers needed replacement was to keep a eye on the temp gages ( if you have them). if you noticed the temp going up slowly through out the season, its time to check them out.
I was told it is easy to replace the impellers. I had the marina do the work. I look at it as a small insurance policy. If I screw up iam S.O.L. if they screw up they make the repairs at no cost to me.
Iam not saying everyone should wait as long as I did, (I just dont like to spend the cash). But Iam all for preventive maintenance!!!!!
Stopped in at Discount marine on John R in Madison Hgts. The impeller in my Alpha one is in the lower unit and even for a first timer am told it should take about 30 mins to change. He also recommends changing it every 3 years or so for safety sake.
If you have a Mercruiser Bravo drive the impeller is in the raw water pump not the lower unit. This pump is belt driven off the engine and is located on the right lower side of the engine block. It is easy to replace if you have access. If access is tight it is a miserable job. Bill272 & I can discuss it anytime your interested
Hey Ed, I actually have mine down to around an hour per side now. It involves using 2 or 3 long peices of clothesline so that different components can be coaxed back into position and nothing falls out of reach. A guy on OSO sent me this method he came up with after having to pull an engine because he dropped the water pump under it and couldn't get it out. The new and improved way is still no picnic and requires painkillers afterwords, just not as many as before.
Port engine took about 3 hours, starboard took 1 1/2 hrs. Not hard but pure hell !
What really pissed me off was the blue impellers I got from George had the old fasion keyways and I didn't have the adapters so I just replaced with Merc.. impellers. Next time around the blue go in.
Tried to get into the storage building last week. Bad news, the lady is in Florida until about mid march and cannot get in.
Pyrate - Don't be scared, you've got an alpha drive. If you move into a boat with twin Bravos, just try to make sure it has some space to access the front of the engines. It actually turns out to be a good arguement for a bigger boat. The real problem is that I'm too cheap to pay someone else to do it, and even if I wasn't, I'm unwilling to give up 2 weekends in the middle of summer waiting to get it fixed.
Thanks for the storage info, Ed. I was hoping to get over there in the next week or two since I've been busy with work (at work now...grrr) and we just got back from a week in Cozumel. Man, do I need summer to get here...