3.0 Mercruiser Impellor Change

[Denis O]

I'm in the middle of an impellor change on my Alpha 1 Gen 2 leg and have some questions. This is my first impellor so have watched a number of youtube videos.

I need to know which way the blades of the impellor should face when they go in the housing. When the housing came out the end of the blades were squeezed in an anti clockwise direction. All the videos I've watched show the end of the blades being bent in a clockwise direction.

Would I be correct in assuming that the blade direction would depend if the leg was in forward or reverse before the leg was removed. That suggest that the drive will go clockwise or anti clockwise dependent upon gear selection. Logically, the only problem with that is, it suggest the impellor is stationary when the boat is not in drive. Surely that can't be correct as it would overheat on tickover or does something else drag water round the system at tickover. Or perhaps, at tickover, the engine doesn't need that amount of cooling.

Any help would be appreciated before I put it all back together.

 

[Rickard]

I wouldn´t care to much about that as the wings tend to end up correct either way. Especially on the Alpha II impeller where the wings are very long

An easy way is to hit the starter and se which way the shaft spins. It wont damage anything
If the outdrive is off the boat look which direction the engine spins and then spin the outdrive incoming shaft in the same direction

 

[annageek]

Would I be correct in assuming that the blade direction would depend if the leg was in forward or reverse before the leg was removed.

The shaft onto which the impeller is keyed always spins the same way (including in neutral). The FWD/REV gear selection is in the gearbox in the lower part of the leg. You should be able to see the interaction of the gear selector shaft (the L-shaped metal shaft) by moving it and rotating the drive shaft.

I did ours the other night, as it happens. Found this video (in two parts) very helpful: https://www.youtube.com/watch?v=SC2b3TonHDQ and https://www.youtube.com/watch?v=eqrRX6Z__-4

Anna.

 

[Denis O]

Thanks Rikard. Put back in as per the youtube stuff.

Thanks for the explanation Anna. That explains why it doesn't overheat in neutral.

I've watched a few videos but not that one. Useful tips on the shaft seal as in pulling the shaft up while holding down the seal. I've had to do mine without alignment tools so hopefully my eyes are good enough to get things central.

Now need to wait for my assistant to put the drive unit back on the leg and fire it up to make sure all is well.

 

[Denis O]

That's it then. All finished and running as it should (on the muffs).

Water coming out the exhaust as it should so obviously the water pipe connected when I put the drive back together The first few litres were a grubby brown but after that, lovely clear water.

Forward and reverse select as they should with no nasty graunching noises so the new gearbox oil is doing it's job.

Temperature goes up to normal and drops back a tad as the stat opens.

It's always a little nerve-racking doing a job for the first time so more pleased than normal that it's worked out well. At least on the driveway!!

I did notice a couple of anodes that looked a little worse for wear. The one fitted to the bottom of the leg where it joins the transom, right by the drain plug and the one behind the prop. Boat doesn't go in the water till Thursday/Friday so I'll probably replace those before. That's if Mercruiser Corfu has any anodes in stock.