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Merc 402 40HP lower unit won't slide all the way in. Yet, I can shift.

M

Merc402Newb

New member
Hello all, I'm working on my first outboard and I've just replaced a water pump. But reconnecting the lower unit is giving me fits. Everything is lining up but I can't get that last inch. Something is giving me resistance, but I can actually shift with it not fully connected. The manual I have says nothing about the plastic piece around my lower shift shaft. I have no idea what position it should be facing and I suspect that might be the issue.
Please let me find a guru that has the answer.
I'm a newb, never even owned or driven a boat. I've got this '80 bass tracker and I've torn it down to an engine and a hull both which I'm rebuilding and I've got her started, now I just have to finish this pump replacement so I can move forward rebuilding the deck.
I have read dozens of conversations on this but nothing that seems to be working for me yet. The water tube connects, everything appears to be lined up. But she's still sitting on the truck straps now for two days while I sit in shame and defeat.
Thanks all!
 
The last inch is getting the splines of the drive shaft lined up with the splined sockets of the bottom of the crankshaft. Some people choose F gear for their removal/installation process just so that they have a prop to turn when it's time to do what you are doing.

Sounds like you have your shifter spline under control, just ensure the lever and the propshaft are talking the same language: On turning the prop by hand, F is locked to the crankshaft (once connected or easy to get the two to line up, for the final inch) CCW, ratcheting CW, N obviously spins, and very importantly, when shifting into R, either the engine has to be running or you have to be rotating the prop by hand as you shift to get the cogs and slows to line up. Once shift lever goes all the way into R, prop is locked in both directions.

Only other thing is the water outlet tube from the water pump has to be lined up with the receptacle....bottom of the block on older engines and some engines have a bracket included to make the "blind" stab easier.
 
That's the way I do it because I like using N for shifter alignment.....gotta grab the flywheel if anything is to turn. With F and R on either side it helps to assure me that I am in the gear I think I am. On convenience, the prop is more convenient for single working guys like me and seems a lot of folks prefer it too who post here and elsewhere. Maybe since you are pulling up on the LU while aligning, the prop is right there and easier for others to grab. Different strokes.
 
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Different strokes for different people yes, if it works for you, that's all that matters.
I always do it in N , on small motors I can reach up jiggle flywheel to get driveshaft splined.
But now if it has the collar an plastic alignment sleeve that sets on shift shaft of lower unit ? If it has been forced before , then there can be burs on splines. If u are sure water tube is aligned, have a helper at remote control and just move handle a little. When it goes up put one bolt in and have helper move f/n/r , and make sure it's shifting rite.
 
Texasmark, just curious what u do by your self on big motors ? I Use spark tester on all plug wires to ground and a trigger hand switch connected to starter an solenoid, to bump . just asking ?
 
I haven’t gotten it yet, I’ve only spent a few minutes with it and it’s hanging on truck straps. I’ve tried shifting through the F/N/R and I can make that sync controller to prop yet I get a stiff resistance and can't get the last inch.
I'll update again tomorrow after taking another look.
I do appreciate the suggestions and did pick up some useful bits, thank you.
-Matt
 
Mikey N.C. said:
Texasmark, just curious what u do by your self on big motors ? I Use spark tester on all plug wires to ground and a trigger hand switch connected to starter an solenoid, to bump . just asking ?
Click to expand...
I'm a farmer and have wire handy so I just plug in all the plugs to their HV caps, do a daisy chain single wrap around all the plug cases in series and find a shiny spot on the engine to terminate the wire.
 
Mikey N.C. said:
Different strokes for different people yes, if it works for you, that's all that matters.
I always do it in N , on small motors I can reach up jiggle flywheel to get driveshaft splined.
But now if it has the collar an plastic alignment sleeve that sets on shift shaft of lower unit ? If it has been forced before , then there can be burs on splines. If u are sure water tube is aligned, have a helper at remote control and just move handle a little. When it goes up put one bolt in and have helper move f/n/r , and make sure it's shifting rite.
Click to expand...


So, I can make it shift right and I can get the bolts all started into the nuts, but I assume I shouldn't force it the last inch by tightening the nuts to annoys breaking something. Are you suggesting that I should try wrenching the bolts tight?
Thanks,
-Matt
 
Do not use the nuts to pull it together !!----It should slide together.------Perhaps a visit to your local boat shop will save you some money !
 
racerone said:
Do not use the nuts to pull it together !!----It should slide together.------Perhaps a visit to your local boat shop will save you some money !
Click to expand...

Yeah that's what I assumed, I haven't went full dumbass on it yet. I'm wondering, if the shaft is turning with the flywheel does that mean I can be confident it's lined up properly, or is it possible the nipple atop the shaft isn't sliding into it's spot? That seems to be about the same size as the the amount if space I'm stuck by.
Thanks,
-Matt
 
I wiggle and tighten, taking up the slack on the nuts, wiggle and take up the slack...rocking the prop or flywheel back and forth. Manual suggests lubing the splines at the top of the drive shaft (shifter shaft needs that too) to aid in this function but caution that no grease is to be used on top of the shaft as it can prevent the shaft from seating properly.....but it ain't any inch worth.
 
Texasmark said:
I wiggle and tighten, taking up the slack on the nuts, wiggle and take up the slack...rocking the prop or flywheel back and forth. Manual suggests lubing the splines at the top of the drive shaft (shifter shaft needs that too) to aid in this function but caution that no grease is to be used on top of the shaft as it can prevent the shaft from seating properly.....but it ain't any inch worth.
Click to expand...


On I finally got it. I’m not even certain what I did different today. I did use the wiggle method, but I think that top nipple just wasn’t going where it was supposed to. It popped right it without effort. If you’re reading this and having the same issue, back out and keep trying until it slides right in. It will.
thanks all for the help!
 
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