1988 100 hp Mariner 4 cyl/2 stroke water pump

[simplydave]

I got this motor along with a project boat and it starts and runs but I do not get immediate tell tale stream indicating the water pump is working properly. The motor was not run for about 6 - 8 months and am wondering if it takes a while (1 minute) for the water to circulate to the point of peeing out the indicator.. I have taken the motor hose and run water backwards through so I know it is not blocked.

Next question. Which service/tune up manual would be suggested for the best bang for the buck?

This is the first merc/mariner I've ever owned. Have always had evinrude or johnson and am unfamiliar with their method of operation.

many thanks for any replies.

 

[simplydave]

well, I pulled the lower unit and changed the water pump impeller and assorted gaskets. Put it back together and still have no water coming out the telltale, none, nada, zip. Old impeller was barely used looking, no cracks, breaks, missing vanes or anything like that. I cannot find a schematic of this motor anywhere, does anyone have any ideas where to find one? Anyone have an idea how long I should run it before it blows up from lack of circulating water?

Is there supposed to be a connector from the water pump to the engine water feed or does the top of the impeller serve that purpose?

 

[racerone]

The outlet from the pump goes to a tube that feeds water up to the motor.

 

[simplydave]

That's what I'm trying to figure out. Is there a plastic extension tube that is supposed to be there? On some evinrudes it's called a "collet tube", On this there wasn't anything when I dropped the l.u. and I cannot find a cooling system diagram showing anything. It's like this motor is a top secret and no one has info on it.

I even went to the public library and they only have a manual that starts with the 1990 models.

 

[racerone]

Not secret at all.----mercruiserparts.com----Has the pictures just for you.

 

[simplydave]

thank you. I went to the local merc shop and bought the tube that goes from the water pump housing to the water tube and installed that. i still have no water coming out the telltale after putting in a new impeller, gaskets, driveshaft key, seal, connecting tube. The motor starts and runs but I am seriously afraid of it locking up running it without visual evidence of it pumping water. I do not want to run it in gear as yet. I've checked the tube from the water jacket to the telltale fitting and it is clear, I've run water through the water jacket fitting and it comes out the exhaust housing. I'm at a loss at this point.

 

[simplydave]

good news. I dropped the lower unit again and took a garden hose with a 3/8 inch tube attachment and stuffed it up the cooling tube. I ran water for about 30 seconds to fill the water jacket and lo and behold I got a stream out of the pee hole. I guess that it takes about a gallon of water to fill the water jacket completely so tomorrow I will fire it up and let it work for a while. I'll keep you all posted on the results.