Is it hard to take the lower unit off a mercruiser 305 to change the water pump?

Question

Is it hard to take the lower unit off a mercruiser 305 to change the water pump?

Answer 1

Depends on what model you have, most are on the front of the engine (not  refering to the normal circulation pump you find in a car too, you will have that pump too).  There is an impeller pump housing that pumps only  "Sea Water" and has a round flat plate with about six to eight screws that hold the cover on (may face backwards).  The pump is driven off the drive (fan) belt assembly and the pump (when you are standing facing the front of the engine) is on the bottom right.

Pull the cover off, take two flat blade screwdrivers and pry the rubber impeller out with even pressure from both sides.  Put some soap on the new one and as you push it in, turn it the direction that it would normally run with your palm until the splines engage, then push straight it.  That way the rubber impellers are laying the way they need to be when running normally.

The impellers you are thinking about are in the lower ends on outboards and some very old models inboards.  Inboards are different in that regard, all the ones that are less than twenty years old are pretty much mounted on the engine instead of the outdrive.

Good luck

Answer 2

These answers didn't do it for me either I have the same Problem

Answer 3

no its not hard and im assuming you have a inboard/outboard  there are 6 nuts between the upper and lower drive first you need to drain the gear oil from the lower unit there is a little plug on the bottom of the lower that has a flat groove in it thats where you drain it from and you have to also pull the same plug on the upper drive on the oppesite of drivers seat it says vent then once drained loosen the bolts and the lower will separate from the upper  and theres a plastic housing that has a few nuts and remove them and theres a little rubber impeller in there and it will slide off the shaft and be careful theres a metal tab that has to go in there or it will not turn the impeller  also replace all gaskets that come with the impeller kit ....you will see the metal tab  as taking off the old one replace with new one and put everything back together and fill with 80-90 weight gear oil from the bottom hole .... its very important to fill from the bottom hole to prevent air getting traped in the gear case fill until it starts seeping from the vent hole up top and put plug back in and your ready to go boating again

its a simple process and once you have done it it is really easy to do

Answer 4

The first two answers are only partly correct.  I think the first thing to do is determine exactly which engine drive you have.  Is this an I/o or straight inboard.  The engine has a circulating water pump, like a car on the front of the engine.  However, it's the "raw water pump" located in the stern drive that fails.  It's not that hard to replace but the boat has to be out of the water. You would need to read and understand the service manual in order to do this job.