What's the difference in these water pump bases???

[kozman01]

I picked up a brand new water pump base at the Merc dealer the other day. Brought it home and compared it to the old one that I had removed from the LU. They look similiar with one exception. If your looking down at the base as it's installed on the driveshaft, on the left side of the base near the front of it, there is an approximately 1/4 of an inch opening. On the old one, this hole is plugged with a plastic stopper. On the new water pump base, there is no hole. Has anyone else noticed this? I saw for myself the number the Merc dealer came up with on his computer screen for the part. Did someone have an improper base previously installed? Does anyone know why the hole in the old one was closed by this small plastic stopper? Also, there are two metal rings that were under the old base. Should these be reinstalled when the new base is put back on? Thanks for any advice in this matter.<br /><br />By the way, 1969 Merc 800 80hp

 

[alcan]

Re: What's the difference in these water pump bases???

I don't understand about the plug you refer to. Some times parts get up graded (Changed). The correct part# for motors ser# 3059820 and under is A46-48747A1. If your ser# is higher than this let me know and maybe I can get you the correct # for your motor.

 

[rodbolt]

Re: What's the difference in these water pump bases???

hello<br /> some of the older inline lowers had a sdew similar to the drain plug screw that you could thead an adaptor directly into the pump base for flushing. not all had it so some had the plug and later versions just never had the plastic machined. anyway the rings you found are probably the driveshaft bearing shims. if someone changed your unit or you unit uses shims under the base to keep yje upper bearing preload you really need to go back and follow the manual before you detonate your unit, its in the section titled shimming the water pump base.<br /> good luck and keep posting

 

[kozanecki01]

Re: What's the difference in these water pump bases???

THank you for the info. The pump number that you mention is the pump I have. Thanks again gentlemen.

 

[rodbolt]

Re: What's the difference in these water pump bases???

hello<br /> what I was referring to about the "rings " they are shims. it is very common to have a much older or newer gearcase on anygiven merc inline. the cases from the inline fours of about75 hp and up to the 150 inline 6's shared about 20 years of physical interchangeability. means almost any large four or inline 6 cylinder case will physically fit your application. the gear ratios were different but you can prop around some of that. now if someone has installed a gearcase that is not in your power head ser # range the parts you bought may have nothing to do with fitting your gear case. that is why I say get the manual out. make sure the parts you have actually are for your case. and remember just because they physically fit dont mean it works.<br /> belive me. in my area we see it all the time. man we got some DR frankenstien mo-kanics about here.ya know the type. rusty bolt bob and his can of krylon and voila its a rebuild. so be aware the base you have may not be the base you need. check the shimming of the lower base. <br /> good luck and keep posting<br /> PS I dont work on mercs much anymore but I think maybe clams can verify what I am saying. maybe he can give ya a bit of gearcase advice

 

[kozanecki01]

Re: What's the difference in these water pump bases???

I contacted the original owner and he advised that all the main parts of the motor and lower unit are original. He can't advise on the water pump. He always had the shop do it for him. There were two metal shims under the old cracked base. The new base is identical in all dimensions witht he exception of that hole on the left side. IT look to me like this water pump thing is getting a little bit more involved than what I thought it would. With the luck I have, I'll put this 30 year old motor that has ran fine for the last thirty years and I'll blow it up. Merc. shop, here I come Thanks for giving me this info. before I did something stupid.

 

[rodbolt]

Re: What's the difference in these water pump bases???

hello<br /> dude did not mean to scare ya. you can measure the distance from the seal area to the gasket area with calipers or depth mics. if there is no difference the shimming will remain the same. if there is you just adjust the shim pack to maintain the original clearence. the shimming procedure is not difficult but it needs to be done. not all techs can do it correctly cause the design changed in the 70's sometime. that is why I try to measure and record shim packs and the depth of the base. that way I can use my micrometer and keep the preload the way it has been for its life span.<br /> dont let me scare ya I just need you to be aware of what is going on and certain things that need to be checked.<br /> good luck and keep posting. <br />ps do you have a service manual?

 

[kozanecki01]

Re: What's the difference in these water pump bases???

I've got an old Clymers manual. I believe it addresses the shim issue. Where am I measuring the gap? Between the base plate and the LU? Do you adjust it by adding or removing shims?

 

[rodbolt]

Re: What's the difference in these water pump bases???

hello<br /> let me double check my service manual before I tell ya something thats no so. I will be a day doing it but I will get back to ya.<br /> the shimming is between the bearing and the base. any way I will post back<br /> good luck and keep posting