OK, I replaced the impeller in my mid 70's 4 hp Mercury outboard. I was told I may have goofed when I put it back together and it may not shift properly. Meaning it's in the wrong gear and I probably only have reverse and neutral (or something like that). My questions are these: 1) How can I tell if it really is wrong and 2) How do I fix that situation if that's so? It's my understanding you need to have the shift lever in a particular position and/or the lower end in a certain position in order for everything to be right when you're finished. I worked on it last summer/fall and haven't put it in the water yet- I don't want to start it up if it's not right. If anyone can describe what I need to do I'd really appreciate it. I have a 'mechanic' that works on my motors but I thought this was something simple enough I could do myself and save a bit. Maybe not?
Thanks!

It all depends on the make and model of your outboard. Some require it to be in forward gear or reverse gear or neutral. Here's what u can do now to see if its on properly. Put the engine in forward gear and spin the propeller clockwise, should spin only clockwise, do the same in reverse, should only spin counter clockwise. Neutral, should spin both ways. Next put ear muffs and garden hose, and test the engine..check for a good stream of water, and test forward, reverse gears and see how the prop spins. Also, look at YouTube videos, there's a bunch which should help you out.

my comment my not be of consequence, but I just rebuilt the lower unit of a 1969 sea king outboard ( 9.2 horse). and the directions for detaching the lower unit were to have it in neutral. I investigated this, and found it being do to creating enough play in the shifting plunger going into the lower unit to be able to separate the two parts and have enough play to get at the screw heads holding the plunger rod together. after I removed the lower unit, the plunger shaft did whatever as it kind of flopped around in the open space it is housed in and in fact changed from neutral to forward. after repairing and returning to unit I saw that the lower unit in drive was to short to connect, (shaft end was below the lip of the lower unit), I then for s and g's shifted the head to drive and then to reverse, ( in reverse the shift plunger was to high in the head portion of the motor to make the connection), so it was not in that instance a big deal, because in order to rejoin the two shaft ends it had to be in neutral, or you could not get enough space to get at the screw heads. I could be way off my rocker though and just got lucky.

Thanks guys. I may get more responses but I'll check out what Barresi suggested, except this particular motor draws the water in through a port on the bottom of the cav plate so I have to put it in a barrel- no ear muffs. Not a problem though, I have one I use to flush it after each use. So I guess I'm not 'over a barrel'! ;-)

Well B. it seems you (and my mechanic) were right. Spins C/W but that's all. I'll have to drop it and try again. Thanks for your help. I'd still like to know what position the shifter needs to be in when re-installing the lower end if anyone knows for sure.
If I don't get any replies before I get to work on it, I'll use trial and error. Then post the results so maybe anyone else who needs that information will be able to get it.

OK folks, for what it's worth, I think I've fixed my problem. I dropped the lower unit on my motor (it's a mid 70's Mercury 4 horse) and put it in neutral, then re-installed it. I put it in a barrel and test ran in and it now seems to operate correctly. Forward moved the water aft ant reverse moved the water forward. Cooling water stream was good- I'd have preferred it a bit stronger but it IS a 30+ year old motor. I still have to test it on the open water but I think it'll be OK. Thanks to Barresi and domkaaj for your input!

Cool prober. Glad to hear it worked out...so far. The true test is out on the water. But if the prop spins in forward and reverse and you have a good cooling stream, then you should be go to go. Now if the cooling stream is too weak, which is doesn't sound like it, it might be the water pump. The only way to know for sure if it starts to over heat. Good luck!