New Impeller (blues) Part II

[tmcalavy]

My thanks to Lonewolf, SeaDawg, Bill G, Alcan and Keg. Your advice/encouragement taught me how to pull the lower unit on my Merc 500 50 hp outboard. Turns out the impeller is good, must have been replaced just before I bought this rig. Bad news is a seal down there is shot...my lower unit lube looks like clabbered milk! Guess I need to take it in and have the seal(s) replaced.<br />Now the really bad news. No matter how this big ole boy holds his mouth, the lower unit won't flush up tight to its base. A 1/8th inch gap remains, no matter what. I think the short splined shaft up front is the culprit, but no matter how I turn it I get the same result. Close but no cigar. I cleaned the splines on the short shaft and there is a rubber eccentric (think that's the term) on it. I can position the shorter splined shaft so the driveshaft and prop shaft are in neutral, but when I put the lower unit up and snug up all the bolts I find i have forward gear and no neutral or reverse. I must be really dense, or am doing something WAY WRONG!

 

[Yepblaze]

Re: New Impeller (blues) Part II

It just takes patience and multiple tries.<br /><br />You will notice that if you turn the small splined shaft. (actually the top half of the brass thing on the small shaft) I believe it's counter clockwise you will notice three noticeable gear positions where the prop free wheels (neutral) Where the prop ratchets forward(forward) And where it ratchets reverse (reverse)<br /><br />It will be somewhat touchy to make it stay in just the right place for nuetral while you slip it up onto the motor that has it's shift set in nuetral gear also. While keeping an eye on the water tube to make sure it enters its socket just right. It might take a slight pull of the start rope to engage the motor/driveshaft splines.<br /><br />It just take patience and multiple tries.

 

[tmcalavy]

Re: New Impeller (blues) Part II

Yeah, I can get all three positions with the small splined shaft. The rubber eccentric on the small splined shaft is forward when its in neutral and it seems it should fit right this way. I can get the lower unit almost flush, with water tube and exhaust jacket in right places, but that aggravating 1/8th gap remains up front (right around the small splined shaft). Wiggling the flywheel or prop shaft doesn't help. How can i check to see that the top of the shift shaft is in the right place? The control lever is in neutral, but I wonder if the top of the shift shaft is not aligned right? Where do I look to check this alignment? I'll get back at it tomorrow. Thanks for all the advice.

 

[Yepblaze]

Re: New Impeller (blues) Part II

The thing on the "shift shaft" is a camlike device that pushes up on a mechanism that moves a hooklike device to secure the motor from lifting in reverse. The force you are feeling might be the actuating mechanism working or working against itself. Not sure if the pic applies but anyway the cam needs to be correctly orientated to the spline for proper operation. <br /><br />

 

[Yepblaze]

Re: New Impeller (blues) Part II

You might also notice the on the upper cam there are two ears that fit into two slots on the upper housing as it goes together.

 

[tmcalavy]

Re: New Impeller (blues) Part II

Thanks a bunch YB, pix is just like my Merc. I decided to replace the impeller anyway, even though it "looked" good, so I made a trip to the boat house to get a new one. Took the lower unit along just in case, and one of the shop guys there showed me where the shaft/cam is supposed to be for neutral, and how to check the upper shift mechanism for being centered on its run. Duh! Put the new impeller in, put the lower unit up and it snugged right up like it should. Now I know how to do this. Nothing like real experience as a teacher, and the others on this board to help us newbie's along. Thanks again, your help was invaluable. Tomorrow I put the cuffs on, she will undoubtedly spit more water than before!