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lower unit will not go back on ! 1993 175 hp

A

artie in miami

New member
I have a pair of counter-rotating Merc 175HP outboards made in 1993 with very low hours (under 100 hrs) that I have had since they were new. I replaced the impeller in the water pump in the counter-rotating engine (port side) and cannot seem to get the lower unit back on. I have done this impeller change a few times already with these engines and have never had a problem like this. I put the engine in gear (forward) and have been turning the prop (clockwise on the counter-rotating engine) to get the driveshaft splines to line up with the part on the crank and I keep hearing the sound of metal against metal...cannot get the last half inch needed to put the nuts on the bolts. I have been through the factory service manual several times and cannot seem to get it. Does anyone have an idea what this could be...it came off very easily...the only thing I can think of is I did not have the engine tilted up all the way...can that keep the lower unit from going on ??
I got the water tube into the top of the water pump just fine...and the gear shift is not hitting yet...there is a space between the shifter rod and the shift shaft in the lower unit...so I know that is not hitting.

Any help would be much appreciated...I have tried it at least 25 times yesterday...what a workout !

Is there some trick that I have forgotten to do ?? Thanks in advance.

artie in miami
 
Re: lower unit will not go back on !

Any chance you got some grease on the top of the driveshaft - not the splines that mate with the crank, but the very top.

If you did, since it has "nowhere to go" it can stop the driveshaft from "going all the way home".

That would be the first thing I check out...
 
Re: lower unit will not go back on !

Galamb
thanks...but that was covered in the manual and I checked it before I even started trying to get this sucker back on...as I turn the prop, it stops as if the splines are lining up..but still cannot get it to go that last little bit ! I am going to end up with arms like "popeye" if I keep trying this...that lower unit is heavy !

a
 
Re: lower unit will not go back on !

Can't help with your exact problem, but I have a small webbing strap I put round the cavitation plate and the "horn" on the back of the outboard midsection. I get the lower up and splines on driveshaft engages, then throw the webbing over and tighten it. Means I don't have to support the lower unit and can use one arm to tweak the lower unit's position and the other to easily turn the prop.
Once it all mates up, tighten the webbing again and you have at least one free hand to start a couple of bolts/nuts in.

Regards, Andrew.
 
double seal trick !

Boy...do I feel stupid ! While looking at the parts diagram on one of the parts suppliers websites...it hit me !! I put a nice, new round seal in the water pump output pipe (on the top of the pump housing)...and never took out the old one !! That is why the lower unit will not go all the way back in...I was in a hurry as it was getting dark and I goofed...is that part of getting old ? I was so shocked at what I found inside the water pump (impeller was all torn and melted...much of it ended up in the space between the stainless cup and the top of the plastic water pump housing...tought to get that out...think I will just replace the whole pump housing. Thanks very much for your help.

artie
 
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