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Mariner/Yamaha 5hp lower unit removal

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swordfish69

New member
Hello all,

I've just purchased a 12' auminium run about that has come with an old, aircooled Mariner/Yamaha 5hp outboard.

Serial #: 661S 034376

The engine is in reasonable condition for a 30+ year old motor, good spark, compression etc. Issue is it appears to be stuck in FWD gear and cannot be changed into reverse. I am trying to remove the lower unit (gear box) to investigate further but have run into a spot of trouble. I've removed the bolts holding the LU on (3 ?) and disconnecteed the shifter rod. A small crack has opened up between the LU and main assembly but I cannot seem to remove it any further. Any insight or suggestions would be greatly appreciated. I can post photos up if that would help.

Thanks.
 
Still no luck - put bolts all back together - fired engine up in hope that vibrations would loosen the drive shaft - but still can't seem to remove LU.

Anyone have any thoughts?

Cheers,
 
You must select reverse before trying to remove the lower unit. Obviously you should throw everything in the bin and buy a new outboard because you can't do this (just joking). If the shift rods still operate but are out of adjustment you could try disconnecting the linkages and operate the shift rod by hand to select reverse. If this is the case you only need to adjust the linkages to correct your issue, no need to remove the lower unit. If this is not the case return to bin option (jokes again). If it is hard to select reverse turn flywheel anti-clockwise to assist gear shifting. Make sure you have disconnected battery and there is no way the outboard can fire up (remove spark plug). You should remove the prop, I assume so you can't chop your leg even if the prop shaft starts turning.

When you still can't select reverse, loosen but do not remove the shift rod locknut.

Rotate the threaded connector until the lower rod is free.

Remove bolts securing the lower unit to the intermediate housing. Apparently only 2 (front and rear-most), the third one must be for securing something else.

Remove lower unit, don't lose the dowels.

On the 5HP units there is a shift rod limit screw on the right side (standing behind prop looking towards outboard) that needs to be removed.

Hope that helps.
 
wynjim55 - Thanks for the advice. Explains why I was having difficulty dropping the lower unit down whilst stuck in F gear! As for the bin suggestion - I'm close to doing that anyway at the moment!!

Turning the flywheel anti-clockwise to assist with the gear shifting unfortunately has not helped the situation. " Rotate the threaded connector until the lower rod is free" which threaded connector are you referring to?

Cheers,


photo (1).jpg photo.jpg
 
Yours (from the photos) clearly doesn't have the threaded connector, instructions given are for wrong lower unit.

I would try removing the trim anode (in first pic above and behind prop) You may find a bolt under there that holds the lower unit to the intermediate housing. If it is done up correctly you won't be able to get a gap when you remove the other bolts, but if it is out a few turns you will get a gap but there will be sufficient thread to prevent the unit separating.
 
Yours (from the photos) clearly doesn't have the threaded connector, instructions given are for wrong lower unit.

I would try removing the trim anode (in first pic above and behind prop) You may find a bolt under there that holds the lower unit to the intermediate housing. If it is done up correctly you won't be able to get a gap when you remove the other bolts, but if it is out a few turns you will get a gap but there will be sufficient thread to prevent the unit separating.
 
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