Re: 1967 650 4cyl. lower unit
First of all, an engine of that age may have corrosion issues that can make the job difficult. So time and penetrating oil are usually part of the process. Look here on iboats for pictures of lower units for sale if your manual doesn't show you what they look like when they come out just to give you an idea what you're after.
Tilting/trimming the engine to full up position makes it easier to do the job.
Basically you remove the screws and nuts holding the two sections together. There can be one in the front and one or a pair on each side and always one under the trim tab. On the trim tab, remove the plastic cap on top of the LU, look down the hole and you will see a hex allen socket screw, 3/16" socket or thereabouts. Unscrew this and the trim tab comes off.....remember which way the the tab is turned so that you can return it there when closing things back up. With the tab removed, look up and under the plate where it was mounted and there is another screw there that is one of the screws holding the lower unit on. The nuts on the side cannot be removed completely until the sections have started to separate so initially, back them off as much as you can. I have used them in the past as a prising point. I'd run them up close to the deflection plate that stops them from coming off initially, and then stick a large screwdriver in the gap and pry. Some prying may be required, some banging with a board and hammer; one guy even hung his upside down with the power head a couple of inches off the floor for a week; all tricks to get it separated. Just remember to get ALL the fastners out or loose(nuts on the side). and remember you are dealing with cast aluminum, so don't get too frisky banging on the thin edges of the antivent plate and other deflectors.
On an engine of that age, I'd replace the whole pump and the (upper lower unit) oil seal on the driveshaft just under the pump assy.
Your kit may contain some parts you don't need as sometimes they are made for several model engines. Pay attention to what your engine currently has installed and only replace like parts.
Before you start, put the shifter in F gear and leave it there for the whole repair. Do not rotate the small shaft at the front of the engine as this is your shift shaft and you want the shifter and the lower unit to both remain in F gear (will see why later).
The cover comes off first with 3-4 screws and under it is the impeller. It comes out and so does a little key that fits in a slot in the crankshaft that has a ridge on it that fits into a grove on the inside of the impeller to lock it to the shaft.....don't forget this key when reinstalling.
Then the bottom plate and all and under that the upper seal to the lower unit which is not part of the water pump, just beneath it.
Installation is the reverse of the removal. Turning the crankshaft cw and putting a little soap on the impeller blades make it fit better. The pump is eccentric so one side will bend the blades way back and the other side will be more relaxed. That is how the pump is able to generate water pressure.
When you get your impeller out, if it has any pieces of blades missing, they could be anywhere in the engine blocking water passages. You need to make a serious attempt at finding them.
In reassy, just a little grease on the splines of the drive shaft, no grease on top so that it won't impede being able to get the shaft to seat all the way. The water tube comes out of the top of the pump and engages a hole in the bottom of the engine block....be sure you get it plugged in or your pump will not be able to pump water into the engine.
In getting the last inch of the separation of the 2 sections to mate, stopping without going all the way together is caused by the splines of the engine and shaft at different positions. When this happens, with slight pressure on the lower unit (pushing against the block) grasp the prop and use it to turn the drive shaft until the splines line up and the thing goes together completely. Also, before you go this last inch, start the nuts on the side of the engine and run them down so that the sections can come together.
I don't know when Merc went from carbon steel to stainless on their drive shaft. I remember being in a shop about '65-'67 time frame and there was a lower unit sitting in a vise and the shaft was obviously carbon steel. Serious rust was everywhere.
So, before you start installing new parts, and may have to do it to get the old parts off, clean up your shaft and when the seals are pushed over the spline at the top, wrap it with paper or something so that the rubber lip of the seal doesn't get cut.
That's a general overview. The manual should do the rest and if you don't like the one you have, Solec manuals are for sale on here. I have a OEM Merc manual for my engine and recently I looked at Seloc and saw a lot there that wasn't in my OEM manual so now I have both.
Mark
