90 merc 115 rebuild done, some remaining water Q's

[h2oTherapy]

To all who have given me advise the last couple months, many, many thanks. After a complete rebuild (my first), I got my 1990 115hp Merc (4cyl) on the water for the first time Sunday and for the most part, everything ran great. I kept the speed down, so I don’t’ know what its like at WOT yet.<br />Question1: When I ran in the driveway with the cover off, I noticed that at start up, water would come out of a hole in the thermostat cover plate. This plate houses both the thermostat, and another device (name?). The hole (looks like it’s supposed to be there, and is positioned on/over the ”other device”. After a while, it stopped flowing out of this hole. What is this device for and why does it let water out?<br />Question2: This whole rebuild was the result of an overheat because 1) the overheat alarm was not functioning (this is fixed), and 2) the water jacket was about 1/4 -1/3 full with sand. Just before the failure, I had noticed that the water **** stream looked very weak as I idled through a no wake channel, but I figured that as long as some water did come out I was OK. At the end of the channel, I went to WOT, and 4-5 min. later, it seized. During the rebuild, I inspected the water impeller and all looked to be in good shape (I had ordered a rebuild kit, but got sent the wrong one, so I didn’t use it), so I didn’t replace it. On the water yesterday, it seemed that the **** stream was still very weak at idle. I had assumed that the low water flow JBF (just before failure) last year was a result of all the sand, that I have since cleaned out, but watching it yesterday, I am not sure. For comparison, I looked at my friends 1995 125 Merc which has a much stronger telltail stream (not that I am comparing sizes or anything).<br />Any thoughts would be helpful.<br />Thanks again,<br />H2oTherapy.

 

[DJ]

Re: 90 merc 115 rebuild done, some remaining water Q's

H2O,<br /><br />REPLACE THAT WATER PUMP. You're playing with fire on a fresh rebuild. I don't think you want to do it again!!

 

[fish man]

Re: 90 merc 115 rebuild done, some remaining water Q's

i have a 1995 115 merc(4 cylinder),shoots a steady stream at idle if that helps

 

[fish man]

Re: 90 merc 115 rebuild done, some remaining water Q's

i have a 1995 115 merc(4 cylinder),shoots a steady stream at idle if that helps

 

[Red De Braal]

Re: 90 merc 115 rebuild done, some remaining water Q's

Fish Man and Djohn are right that pisser should squirt. Mine does ! Get that water squirting!!!<br />Good Luck<br /><br />Red

 

[Valv]

Re: 90 merc 115 rebuild done, some remaining water Q's

I cannot understand very well what the hole on thermostat cover is, but you have a temp sending unit and a plug to drain water up there. Be sure drain is close or water won't pressuruze. On the other side if plug was missing you should see a lot of water coming from it. While motor is running on a tank or hose, feel if head gets too hot or it stays just warm. I agree with others, check why telltale stream is weak and if it cools properly. Also don't run motor dry, even a lot of cranking with dry pump can damage impeller. Test it at least with water muffs on, if not in a tank.

 

[h2oTherapy]

Re: 90 merc 115 rebuild done, some remaining water Q's

Thanks all,<br />I am picking up a rebuild kit for the pump today.<br />I know the drain plug you are talking about, its not that. Mercury calls this device a "poppet valve", but I still have no idea what its purpose is, or why it leaks out water. I will pull apart tonight to make sure I didn't mess up the rubber diaphram that sits in there.<br />Any one know what this "poppit valve" is for?<br />H2o

 

[h2oTherapy]

Re: 90 merc 115 rebuild done, some remaining water Q's

update: poppit valve is fixed, does not spew water anymore. I rebuilt the water pump, new impeller, gaskets etc. the telltail stream seems a little stronger, but not much.<br />Q: when running with the muffs, should I be seeing any water leaking from any where besides the tell tail and around the muffs? I have water coming out the exaust, some coming out small holes in the lower unit gear box, water coming out around the shift shaft..... Doesn't seem right.<br />h2o