Yamaha Lower Unit Shaft Question

[jriling]

I just purchased a new lower unit for my 1987 90hp. My original unit's drive shaft has a spring loaded pin at the top which I assume preloads a bearing. The new one does not, is this an issue?<br />Thanks in advance for any help.<br /><br />-JR

 

[rodbolt]

Re: Yamaha Lower Unit Shaft Question

hello<br /> the newer units use a wave washer and lock coller set up on top of the impeller I believe. all the sprind loading does is keep the shaft from chattering at low speeds.<br /> is this a new new lower unit or a new to the engine lower unit ?<br />there is a chart on lower unit interchangeability in the yamaha tech guide

 

[jriling]

Re: Yamaha Lower Unit Shaft Question

First, Thanks rodbolt for the prompt reply!<br />This is a brand new lower unit purchased from Yamaha. The other difference is there is no washdown port/plug on it and the water intake ports are a bit smaller. Other than that it bolted up fine, boat runs good. One more thing,<br />going into reverse is "spongy", sometimes I have to go in and out of gear twice to engage. I have new Morse Xtreme cables so we can take that out of the equation. Thanks again, these forums are a lifesaver!<br /><br />-JR

 

[rodbolt]

Re: Yamaha Lower Unit Shaft Question

after rereading your post I missed the spring on top. the older units used a tapered bearing with the race below the bearing. the later units used a different bearing. the spring loaded pin was used to maintain bearing preload and prevent chatter at low speeds. merc did it for years. but the spongy engagement needs to be addresed. its either the box or the cables the adjustment or the shift shaft. sometimes the shift shafts in the midsection rust away. the first sign is difficulty finding reverse. it can cause a lower unit failure if not addressed.