Replacing water pump impeller for first time

[stevh1155]

From what I've read, it seems pulling the LU off and replacing the impeller and all the gaskets is fairly easy, however sliding the lower unit back on can be a bit of a nightmare! I have the Mercury service manual for my motor (1978 1150 ELPT), and it states to First shift into forward gear, then tilt motor until stop lever can be engaged. Then shift engine to neutral gear and begin removing the nuts and bolts. I have no idea how heavy these are but I'm guessing around 35 lbs. or so? My plan is to use a ratchet strap for support while I put things back together and to use a marker on the shift shaft when it comes off so I can get it back in the exact position it was in. No one's going to be touching the shifter up at the helm, so that shouldn't move. I've read many threads ad nauseum about doing this and each uses a little different method, so I thought I would just try going by the book. I have a Quicksilver pump kit that looks like it has all the right parts. I just bought this boat last fall and have been putting this off too long...anyway, to all of you that have done this many times, does this all sound about right? Thanks!

 

[racerone]

Leave it in forward when you take the lower unit off.----Replace impeller.---Slide it back together.----Have an assistant rotate flywheel to engage driveshaft splines.----Easy project.

 

[Chris1956]

You will want to replace the impeller, ss wearplate and 2 gaskets as a minimum. Check water pump base for melting (looks like scratches). Replace if found. Check SS liner in upper waterpump. If scratched, replace upper water pump.

I take the gearcase off and install it in neutral. I find that much easier.

Make sure plastic shift rod fitting is in midsection. Be prepared to wiggle shift handle to mate it with gearcase.

Gearcase is 40-50#. If the motor is tilted up, it is manageable. Grease shift rod and driveshaft splines before reassembly.

 

[Jeff J]

The splines never line up for me if I leave it in neutral and when it is in neutral there is no way to line up the splines. I leave them in gear so I can align the splines by turning the prop shaft.

Tilting it up to use the motor latch is a safety thing that cannot be done on a lot of pontoon boats because the motor will not tilt that high.

 

[Chris1956]

Jeff, you could turn the flywheel to align the splines. A 1/2" socket on one of the outer flywheel bolts does the job. I usually use a lifting eye, with the handle of my ball peen hammer thru it as a lever.

You can also move the gearcase rotationally before installing the water tube. That will sometimes align it.

 

[Jeff J]

Yep, I know all of that. I can’t reach the flywheel while holding a lower unit and rotating the prop shaft is a lot easier and faster than rigging up something special. I mostly work on 150-250 hp four strokes and my F70. I have gotten to where I have to use a jack to get the 250 back together. That’s a lot of weight to be screwing around with when it won’t line up.

 

[Chris1956]

Jeff, I have always been able to reach the flywheel while holding the gearcase in place. Of course, my speedboat is a low boat, making that easy.

If I try to install the gearcase in forward gear, often the shift splines will not align properly and the engine will not shift into reverse or sometimes even neutral, and the shifter needs to be turned CCW in forward to align it properly.

It therefore makes sense for me to install the gearcase in neutral, as that is a positive detent, unlike both forward and reverse which have many degrees of turning freedom.

 

[stevh1155]

Jeff, I have always been able to reach the flywheel while holding the gearcase in place. Of course, my speedboat is a low boat, making that easy.

If I try to install the gearcase in forward gear, often the shift splines will not align properly and the engine will not shift into reverse or sometimes even neutral, and the shifter needs to be turned CCW in forward to align it properly.

It therefore makes sense for me to install the gearcase in neutral, as that is a positive detent, unlike both forward and reverse which have many degrees of turning freedom.

That's the way that the Mercury service manual says to do it, but what I didn't understand was why they tell you to start off in forward gear before you tilt the motor all the way up and then shift to neutral after the latch is locked.

 

[racerone]

Forward gear releases the reverse lock , so motor can be tilted up.

 

[stevh1155]

Do trim models have a mechanical reverse lock mechanism, or is it handled with the power trim? I looked and I just don't see anything that would engage the tilt angle pin. I can raise or lower the motor in neutral or forward (I didn't try in reverse). The service manual describes how to check the reverse lock on models WITHOUT power trim but doesn't say anything on models with PT. I just tried to swing the motor back, and it doesn't budge in any gear, feels like something solid is preventing it...maybe hydraulic lock?

 

[Jeff J]

Must be an old Mercury thing. The gear selected has never had a bearing on anything I owned with power trim. My first one was a 35 or 40 hp Johnson in the early to mid nineties. Replaced it with a new Force. Then an Evinrude and now a Yamaha. They all tilted full up no matter where the shifter was. I work on bigger Mercs, Suzukis, Hondas and Yamahas. I don’t think any of them are restricted as to when they can be tilted full up.

My 2-stroke experience is pretty limited but I have never had a problem with the shifter moving when replacing an impeller. I wipe it off and put fresh grease on it but I don’t turn it. I replaced a prop shaft in a 175hp Suzuki once. I think that is the only time I ever had to monkey with the shift shaft to reinstall the lower unit.

 

[stevh1155]

After I investigated a little further, I see a label on the power trim pump that says to enable reverse lock to turn it one way, and to disable turn it the other way. So, aha, that is how it works! I would assume there's some built-in safety mechanism to allow the motor to swing up if you hit an object in the water? (I hope!)