up/dn driveshaft play: 18hp OMC lower unit

[markjewell]

Hi folks,<br />1961 evinrude 18 hp. Is there a "standard" amount of up/down play when the lower unit is all together? I know that there is a shim on the back<br />of the pinion gear, but they only make one size shim, and the manual only calls for one of these standard size shims.<br />I have 2 lower units. One has about 1/4 inch play, but the other on has about 3/4 of up/down play!!! I would think that this pinion gear on the end of the driveshaft would NOT just "float"<br />there!!!<br />The pinion gear is retained on the end of the driveshaft with an e-clip, which is there.<br />I just find it hard to believe that this driveshaft can just move up and down willy-nilly.<br />Any input would be greatly appreciated.

 

[Greg Moss]

Re: up/dn driveshaft play: 18hp OMC lower unit

is that up down play with the water pump on it. It has a pin in the pump that will let it slide up and down the length of the keyway of the impeller. Look and see the pinion doesnot have a nut on that unit the drive shaft just slide into the pinion gear. One of your pumps might have a pump twith a woodruf key and the other a dowel pin for the puimp key.

 

[markjewell]

Re: up/dn driveshaft play: 18hp OMC lower unit

by the way, this is a "bushed" housing, not roller bearing.

 

[markjewell]

Re: up/dn driveshaft play: 18hp OMC lower unit

Thanks Greg,<br />The on with the 1/4 inch play has a dowel pin set up for the impeller, and yes, this play is with the pumps on.<br />I just bought the other lower unit on E-bay and have not taken it apart yet.<br />I bought the 2nd lower unit, as my driveshaft bushings are very sloppy and allowing water to enter into the seal area under the impeller.<br />I don't think that these bronze bushings are replaceable!!<br />Do you think that they designed these lower units<br />with the intention to allow these pinion gears to "float" up and down?? Sounds hard to believe??

 

[Chinewalker]

Re: up/dn driveshaft play: 18hp OMC lower unit

Hi Mark,<br /> Your pinion gear isn't doing the floating - it's just the driveshaft. The driveshaft would normally be limited in its upward movement by the crankshaft. The driveshaft is splined into the pinion gear and isn't firmly attached to it. The pinion gear shouldn't be moving up or down much at all when the other gears are in place to hold it in place. The nature of the bevel in the gears is to push the pinion upwards against it's bushing while the motor is running.<br /><br /> As for bushing replacement - it's possible if you've got access to a machine shop. They didn't make them easy to replace...<br />- Scott

 

[markjewell]

Re: up/dn driveshaft play: 18hp OMC lower unit

Hi Scott,<br />That all makes sense to me!!<br />You are right about the driveshaft being splined into the pinion. I guess this spline just just rides up and down in the pinion gear.<br />As for the bushings, do you think they could be purchased from OMC?? I have a complete set of reamers, maybe if I could find the bushings, I could do a new install. I know that the driveshaft has a .500 inch O.D.<br />Thanks again,