Lower Unit help

[fatpoint]

Engine: 75 Merc 850 - 85hp<br />Problem: Can't get Lower Unit back on.<br /><br />I recently dropped the LU to replace the impeller for she wasn't pumping any water. I got the pump rebuilt and the LU back on but when I did I had no changes in the gears when I tried the throtle. <br /><br />The pump pumped like a champ though! <br /><br />So I took the LU off again and tried again.<br /><br />It seems the linkage on the LU (shift rod) seems to be whats hanging me up. The splines dont line up when the LU end of it in neutral (prop spins freely)and the other end in the exhaust shaft.<br /><br />I must not have something lined up or I should have something in gear to get this to get back on. Im sure its something simple...well I hope it is! <br /><br />Any help with this would be AWESOME!!!<br /><br />Thanks in advance,<br /><br />Matt Collen<br />Knot4You

 

[emckelvy]

Re: Lower Unit help

Mark, the best way to do that is to disconnect the shift cable from the shift arm on the inside of the motor. The shift cable's adjustment here may be interfering with the ability to line up the splines. You'll need to first disconnect the throttle cable in order to gain access to the shift cable's connection.<br /><br />Set the lower unit in neutral, then with the shift arm free, you can move it about slightly in order to engage the shift shaft splines.<br /><br />Make sure the black plastic guide piece is seated fully in the center section(exhaust tower). This piece helps keep the upper shift shaft in position.<br /><br />Something else that can bind when inserting the lower unit is the exhaust tube. Make sure there's no salt or other deposits around the rubber gasket in the lower unit, where the tube engages. Put some Sta-Lube blue boat bearing grease or similar on the rubber and on the tube. Also put a little grease on the end of the water tube, or smear some on the water tube grommet in the pump body.<br /><br />Ensure the plastic water tube guide sleeve is fully seated in the upper pump body.<br /><br />When you put the L/U up, you'll find that you first start engaging the water tube, then as you continue everything else starts to catch. When you get so far and it's all lining up, you'll need to have a 2nd set of hands rotate the flywheel a bit clockwise, to help the driveshaft and crankshaft engage each other.<br /><br />That's about all the trouble areas I can think of, if you have the above all set up she should slide home pretty good.<br /><br />Adjust the shift and throttle cables for proper action afterwards. You'll want a slight preload in the neutral direction to get good shifting action. Make sure you shift back and forth while someone turns the prop by hand, to make sure it's engaging reverse/fwd right and goes back into neutral from either gear.<br /><br />The throttle cable should be adjusted such that there's a little force pushing against the idle speed stop. Just enough so that when you raise the fast idle lever and then return, it returns to the stop. If you get too much preload here, your fast idle won't work well.<br /><br />HTH.........ed

 

[fatpoint]

Re: Lower Unit help

Set the lower unit in neutral, then with the shift arm free, you can move it about slightly in order to engage the shift shaft splines.

Now the lower unit is in neutral when the prop spins freely correct? And when you say move it slightly what am I turning? The shaft that is coming down to the LU. If I spin the splines in the LU I will take it our of neutral.<br /><br />

Make sure the black plastic guide piece is seated fully in the center section(exhaust tower). This piece helps keep the upper shift shaft in position.

When you say seated fully...how far up the exhaust shaft should it slide? It seems like it sits about a 1/8 of an inch from flush but it looks like it could slide up further. Should it be sliding up further? Prolly not I bet.

 

[emckelvy]

Re: Lower Unit help

Move the upper shift arm (the one that you've detached the shift cable from) a few degrees while you're pushing the lower unit up. This helps the internal splines in the upper part of the shifting mechanism mesh with the external splines on the shift shaft in the lower unit. <br /><br />The problem seems to be, with the shift cable hooked up, it's just a bit off and that's keeping the splines from engaging. I've had these before that just slid back on like butter, then other ones are onery and fight you all the way. By disconnecting the shift cable at the motor, it's very easy to move the shift arm a bit and that'll usually do it.<br /><br />The black guide piece, from what I recall, recesses up into the center section (exhaust tower). If you have a reverse lockout, the rod pokes thru it.<br /><br />In addition, this guide piece is what positions the upper shift rod so it's centered and can engage the shift shaft in the lower unit. If you pull this black piece out, you'll see it's got 2 tangs which engage the slotted portion of the center section. You'll also see, on the upper side of the guide, how it's recessed and the upper shift shaft will go down inside it.<br /><br />If the guide is not going in fully, maybe there's some corrosion or debris in there that's keeping it from going all the way in.<br /><br />HTH, if you've got any more ques just post........ed

 

[fatpoint]

Re: Lower Unit help

Ed,<br /><br />Thanks for the help, I got it back on last night. The real trick was turning the fly wheel. Taking the plugs out made it easy turn and then its started to come up, once it was up enough we slaped a couple of the nuts on and drew it right up.<br /><br />One quick question...in the vents above the trim tab, how much water should be coming out of there if any at all?<br /><br />Thanks again Ed for all your help.

 

[emckelvy]

Re: Lower Unit help

Some water may spill out the vents. I assume you're running on the flusher, yes?<br /><br />When you run on the flusher, be sure you have just enough water pressure that some water spills out around the muffs. That way you know the suction side of the lower unit is completely flooded, but you're not overpressurizing the motor.<br /><br />You can tell if you're getting good circulation thru the motor if you have water coming out the prop, and it's warmer than the water going in.<br /><br />Of course the telltale should be going, if not blow compressed air up the tube to clear out any obstructions.<br /><br />Sometimes you see water coming out of the vents but not usually a lot. Mostly it dumps down the center section and goes out the prop.<br /><br />Feel the exhaust manifold cover, it should be cool or at most lukewarm. The block should never feel more than lukewarm on a flusher, as there's no thermostat on this motor.<br /><br />BTW don't rev the motor up much on the flusher, it's not good for the bearings. Never more than 1500, 1200 is better.<br /><br />Glad to have been of help, now get out there and get wet!...........ed