When changing water impeller do I HAVE to drain the lower unit??

I have a 1969 50hp mercury. I want to go through the water pump and change the impeller. Do I have to drain the lower unit, I have just changed it out and see no reason to do so.


Thanks for the help!!

Re: When changing water impeller do I HAVE to drain the lower unit??

I'm no expert, but i think I can handle this one. The answer is no. You don't need to drain LU to change the impeller. I have a 1974 50hp and I've been chasing an overheating issue lately. I've had the LU off several times recently without draining anything. Just remove the water pump cover and change the impeller.

Re: When changing water impeller do I HAVE to drain the lower unit??

Thanks !! Sometimes its the little questions.

Re: When changing water impeller do I HAVE to drain the lower unit??

I assume this is just for your particular motor. I don't see how I can change the impeller without draining lower unit oil on a 1984 Mercruiser 140.

Re: When changing water impeller do I HAVE to drain the lower unit??

They all the same. been that way forever.

Re: When changing water impeller do I HAVE to drain the lower unit??

I'm curious to know, did you get advice to drain the lower unit from a Clymer manual? I have a Clymer manual for my engine (1984 50 hp Mariner) and it says to drain before removal, but the OEM service manual produced by Mercury does not say to drain. I did the impeller swap just recently without draining and had no problems. I'm not an expert and can't say for sure, but I'd venture to guess that your engine is similar and okay to remove without draining.

Re: When changing water impeller do I HAVE to drain the lower unit??

No I dont have a Clymer manual. I just thought that one up, I saw no reason to drain the LU. This forum rocks teh guys really know what they are doing!

Re: When changing water impeller do I HAVE to drain the lower unit??

Fishsqueezer:

I think if you double check your Clymer manual, it says to withdraw the gearbox from the housing and then drain the oil. It does not say you have to drain the oil for gearbox removal.


Remove stud nut from location
(3), and stud nut (5) if so
equipped, then withdraw the lower unit
gearcase assembly.

NOTE: Do not lose plunger (67—Fig.
MR24-32) or spring (68) on 45 and 50 hp
models.

Remove plugs and drain oil from housing,
then secure gearcase in a soft-jawed
vise, with propeller up.

Gerry

Re: When changing water impeller do I HAVE to drain the lower unit??

MOXIEBOY:

Sterndrives are different than outboards. On the outboards, the lower unit is a sealed unit (Gear lube is self contained), in a stern drive, the gear lube also goes from the lower unit up to the upper gears. So when you drop the lower unit, all of the gear lube from the upper gears will drain out. That means when you re-install the lower unit, you will have to add more gear lube and that means removing the lower plug on the lower unit. If it were me, I would go ahead and drain the gear lube, collect it in a container and if it's clean and not old, I would just put it back in after re-installing the lower unit.

HTH, Craig

Re: When changing water impeller do I HAVE to drain the lower unit??

The Mercury service manual explains lower unit removal in 5 simple to understand steps which do not include draining the gear housing.


I did double check the Clymer manual to make sure I was correct. The Clymer manual I have (ISBN: 0-89278-401-5) says to drain the lower unit in step 5 of the removal process. It is not until step 14 in the Clymer book that the lower unit is actually separated from the drive shaft housing. It does, without question, say to drain before removal. However, in my opinion, the Clymer book is near worthless and I don't follow any of the procedures in it since it differs so drastically from the steps in the Mercury service manual. Well, I take that back, the Clymer book is a fine knee pad, as others here have explained.

My point is you’re probably ok to pull the LU off your outboard without draining the gear housing if your Merc. is similar to my 1985 50 hp.

Re: When changing water impeller do I HAVE to drain the lower unit??

Thanks for all the info guys....