Merc 115 Water Pump Question

[gman1001]

I'm prepping the 18' SC for the season and attempting a water pump replacement. I've done it before on other engines - just not this one. Hoping someone here knows a bit about merc lower units. (specifically water pumps)

NOTE: I have the Official Merc Manual for this motor.

HP: 115
CYL: Inline 6
Year 1988

I've attached two pictures of the existing pump on the lower unit which is on my workbench & a parts diagram of the pump. I immediately noticed that their appeared to be two missing parts.
1) MERC Part #: 38970 - Rubber Seal water inlet
2) MERC Part #: Guide Sleeve water inlet

You can see these parts in one of the pictures listed as 25 & 35.

I noticed that there appears to be a tube that might line up with the water inlet on the pump that remains in the leg of the motor. I gave it a little wiggle and it doesn't really budge. Could this be the water inlet Sleeve?(part 35 in diagram)

The telltale on the motor worked fine the one time I ran the motor. the water at idle didn't gush out but kind of chugged. So I know the pump was working at least a little.

Any advice thoughts much appreciated...

[bridgeman]

Should be a thin plastic tube that slides into the outlet, it might be stuck on the tube in the midsection. The tube is used to align the plumbing when putting it back together. Get the shaft splines started first and then align the water pump tube and then the shift linkage and then start the fasteners. PIA the first time but not too difficult.

[gman1001]

Thank you! Turns out that thin plastic tube (white) fell out when I took the lower unit off and rolled down the driveway. I didnt know what the heck it was till I saw the new one in the parts box!

All makes sense now. Thanks again for the reply.

[joshmon71]

Think you need one of these Mercs on the back

http://www.simonmotorsports.com/page13.html

[gman1001]

woah - i'd get into a bit of trouble with something like that on the back of my boat! Ferry to Block Island honey - who needs it!

[joshmon71]

I am prob gonna have that shop reflash my verado ECM to a 275 Verado from current OEM 250, since am out of warranty. Yeah, crazy engines! Note though he has things like a ligherweight balanced flywheel that can add HP, might be a short money add-on. Nice guy, no affiliation there whatsoever just called him yesterday and was chuckling at those videos.

Are you the same gman on another forum posts advice about spinning/jigging?

[gman1001]

Nope - only use that name on the hearth.com (my woodstove) and mapletrader (my Maple Syrup biz)

Real name: Garrett

[gman1001]

Hey there quick question... Can you tell me if the impeller needs to be seated into its housing with the fins directionally correct? I'm not sure what direction the drive shaft turns....

Basically I'm wondering if the fins will self correct to their correct position after firing up the motor.

Tx!

[Fr. Frank]

Seat the impeller by twisting the driveshaft clockwise while seating the impeller housing. If you get it backwards, the vanes MAY self correct, or may not, and then shortly thereafter fatigue and break, sending little pieces of rubber to clog your water jacket and over heat your motor costing you lots and lots of money and frustration.

If you're not sure if you seated it correctly, by all means, take it apart and do it again.

[gman1001]

Thank you! Seemed to work well - the unit has been put back together nicely. How do you know the fins of the impeller are correct however? I lightly greased the impeller cup and after having put it back together I can turn the drive shaft with one hand but its not easy.

Funny I bought the official Merc manual for this Straight 6 motor thinking this procedure would be included. Nope!

Again thanks for your input - very much appreciated as its obvious you know what your talking about!