mercury tower of power cooling

[1979checkmate]

Hello all,
I have a 1979 mercury 115hp inline 6. A few years ago, i ran the motor with no water (water to the muffs got shut off - long story.) I caught it before the motor overheated and immediately replaced the entire water pump assembly, the impeller had melted and fallen apart. However, ever since i have only gotten a very weak stream/spittle/steam from the tell-tale at idle speed. A good stream develops if i bump the motor up just above an idle, and a very strong stream is present at all planing speeds. I feel like the water pump is pumping at the lower rpm's because i have never had the motor overheat on me and when on the muffs and the tell-tale just spitting, the water coming out the prop with the exhaust is luke-warm. However, it is still very nerve-racking for me when i look back in a no-wake zone and do not see the stream that i know should be there. Is it possible that debris is clogging the tell-tale at the lower speeds? Any way to clean out the entire cooling system of debris? I do pull the lower unit at least once a year and inspect/replace the impeller. This unit sees very little use (10-15 hours/year). I appreciate any help!

 

[sourbsted]

Re: mercury tower of power cooling

My I6 1500 done the same thing before the pee hole blocked due to corrosion. Does it go in saltwater? You can stick a bit of wire in there to free it up. After a while the wire trick won't work and it will block up completely.
I just pulled the rear water jacket off and cleaned it out. It works well now.
If it doesn't see saltwater then it must be a debris

 

[Maxz695]

Re: mercury tower of power cooling

Did you retrieve all the broken vains from the old impellor? If you missed any theres the slightest chance one can be stuck between the base and the water pick up screen. If it went up the water tube then it or several fine are moving around either in the baseplate or the exhaust cover and creating a temporary blockage when filling with water. They could have made it as far as the rear cover. Back flushing can be tryed usually better with the LU and water tube removed to try to get the fins out. If you are not sucessful removing the power head will have to be done to insure you have a constant steady flow at all times. I would not trust an intemintant stream and it could cost you the engine. Exhaust all efforts to free the blockage before undergoing this proceedure. It could come to removing the exhaust port cover and baffle but they are a pain to get re sealed as heat warps the cases and block surface over time. Cracking of bolts splitting the case or plates and other issues could arise.
You can try flushing the block through the rear jacket after removing the base and the rear cover which is a lot easier to reassemble if need be.

 

[Chris1956]

Re: mercury tower of power cooling

Those telltales clog easily. Best to install a water pressure gauge in the dashboard and monitor. You will need to remove the plastic elbow that connects to the telltale line, and install a brass tee to service the telltale and the pressure gauge.

Water pressure is very low at idle, and rises to 5-7 PSI at cruise. Look for a 0-15 PSI gauge

 

[Georgesalmon]

Re: mercury tower of power cooling

I also have a 1979 inline 115. My pee stream is not as much at idle in the water or on the muffs as it is when I'm above 1500 rpm. Don't know what you mean by "weak" but it won't be nearly as strong at idle rpm as it is when its going fast. Once you cheak for blockages as mentiond above and if you don't have any you may be just "normal"

 

[Joeshow]

Re: mercury tower of power cooling

Those telltales clog easily. Best to install a water pressure gauge in the dashboard and monitor. You will need to remove the plastic elbow that connects to the telltale line, and install a brass tee to service the telltale and the pressure gauge.

Water pressure is very low at idle, and rises to 5-7 PSI at cruise. Look for a 0-15 PSI gauge

i second the pressure gauge, it is the true telltale... sure the pee hole might be gummed up or blocked but a pressure gauge will tell you if the engine is getting the proper amount of circulating water. my 1980 head (dome jacket) has a plug in it for a pressure gauge that i'll be installing in spring.

 

[1979checkmate]

Re: mercury tower of power cooling

Thanks everyone, a water pressure gauge is high on the list of things to get. Working on a college student's budget i have to carefully weigh what to spend money on. I did replace the impeller today and the copper pickup tube came out with the water pump. I think the pickup tube may have been just setting against baseplate and pushed too far in to the upper pump housing. I got the copper tube set back into the seal on the baseplate, so hopefully that will fix my problem.

Many thanks!

 

[Maxz695]

Re: mercury tower of power cooling

Caution to the wind. Two thing to worry about now. If the tube does not hold on it,s own into the baseplate then the gromet is worn, melted or just plain petrified, and could lose pressure spraying the midsection rather than pushing up into the block where it,s needed, and problem 2 is if the exhaust adapter gasket is leaking it will be heating the housing that holds the gromet for the water tube and will not get better but worse and the pressure wil soon become next to nothing and pee stream wil be severly affected. Keep this in mind save it to you Word pad and make a file or whatever even ignor it, but I,m not gonna repost in the future if this becomes your problem over a very inexpensive part and a lot of preventitive work. JMO. Close thread

 

[1979checkmate]

Re: mercury tower of power cooling

Caution to the wind. Two thing to worry about now. If the tube does not hold on it,s own into the baseplate then the gromet is worn, melted or just plain petrified, and could lose pressure spraying the midsection rather than pushing up into the block where it,s needed, and problem 2 is if the exhaust adapter gasket is leaking it will be heating the housing that holds the gromet for the water tube and will not get better but worse and the pressure wil soon become next to nothing and pee stream wil be severly affected. Keep this in mind save it to you Word pad and make a file or whatever even ignor it, but I,m not gonna repost in the future if this becomes your problem over a very inexpensive part and a lot of preventitive work. JMO. Close thread

A snide remark is not exactly what i was going for, but thanks for trying. The pickup tube had to be lubricated and tapped into the grommet and made a very nice seal. My guess is a previous owner or shop pulled out the pickup tube and did not get it installed correctly and i missed it the first time i replaced the impeller. There is even a slight possibility that i was the one that dislodged the tube the during the original repair. I am a very competent home mechanic and do all repairs and maintenance myself. I am very skilled with a wrench and am also late in my studies in mechanical engineering and am very aware of the sciences at play in this scenario. As i said, a pressure gauge is high on the list and will likely be installed before the first launch of the season. Also, i inspected the exhaust adapter gasket and it is sealing. I do appreciate your thoughts but please leave out the snide and sarcastic remarks next time.

 

[Maxz695]

Re: mercury tower of power cooling

In knowing that i,m sure your problem has been licked. No snide remark just a heads up, if the tube was not secure thats all have a nice trip hope all goes well. I,m not knocking you I just wanted to give you information that is sometimes a seriously overlooked matter to save your engine not mine. Please have a nice night. Also PS Tappered tube? Who tapered the tube? It must be a sealed secure fit to hold pressure just sayin bro don,t be offended. I,m here free of charge trying to help others not be a a hard headed know it al.l Heck I know nothing, but like you i put time hard work and alot of money and searching into this andmy work as well as my opinions. I was here to help not down you or your abilities. Best wishes. Just one ore thing I don,t recall you removing the powerhead to inspect the exhast seal so bro go fo it. or ignor it like i said.

 

[1979checkmate]

Re: mercury tower of power cooling

In knowing that i,m sure your problem has been licked. No snide remark just a heads up, if the tube was not secure thats all have a nice trip hope all goes well. I,m not knocking you I just wanted to give you information that is sometimes a seriously overlooked matter to save your engine not mine. Please have a nice night. Also PS Tappered tube? Who tapered the tube? It must be a sealed secure fit to hold pressure just sayin bro don,t be offended. I,m here free of charge trying to help others not be a a hard headed know it al.l Heck I know nothing, but like you i put time hard work and alot of money and searching into this andmy work as well as my opinions. I was here to help not down you or your abilities. Best wishes. Just one ore thing I don,t recall you removing the powerhead to inspect the exhast seal so bro go fo it. or ignor it like i said.

Okay, i do apologize as i do occasional incorrectly read posts and think the tone or attitude of the post is not what the poster intended. As i said, i do very much appreciate your input. The tube is not tapered, i believe i said i tapped the tube into its seat and insured a good seal via inspection. Also, as soon as i can i will test the motor and water pump for correct operation (hopefully with a water pressure gauge). I think i thought you were talking about the seal from the exhaust "pipe" to the lower unit, which is good. Which seal are you speaking of? I have never pulled the power head as the motor has never displayed major running malfunctions. In fact, other than the low water volume out the tell-tale at idle speeds only, the motor ticks right along beautifully. Again, i do genuinely apologize for overreacting

Alex

 

[Maxz695]

Re: mercury tower of power cooling

There is a gasket that is positioned under the baseplate that goes between it and and adapter for the upper part of the exhaust tube. The exhaust tube when shoved up through the midsection connects to the exhaust adapter. Sometimes the gasket blows and hot exhaust escapes. This hot exhaust can be directed towards the plastic water tube gromet housing. It can litterally melt the housing and deform the rubber gromet the water tube is sealed by in the upper part of the midsection. For now the best thing to do is a very careful inspection with a powerful flashlight. check very good at the water tube housing for melting or deformation. If there looks to be serious damage to it. I would consider removing the power head and redoing the gasket for the exhaust adapter replace the gasket and gromet for the water tube housing, as well as the housing itself if really in bad shape. Thing is heat after time makes rubber turn hard and brittle and could be cracked or dried up and there may be some water escaping back into the midsection rather than being sent into the engine water ports. limiting pressure. When you stick the water tube up in the housing it should hold firm and not slip out too easily. If it holds tight and there seems to be no distortion of he housing you should be fine. Good luck. P.S. The information I post may or may not be the problem you are having just a possible reason to be looked into and any other reader with a similar pressure condition may read and use to there benefit. It is quite possible that your thermostat is sticking half way open and water pressure opens it more under more presuure. I just wanted all avenues to be covered before you reassemble and might have never found the reason if in fact this is the issue I have posted. Cheers

 

[Maxz695]

Re: mercury tower of power cooling

I dont know if this is the same model or not but it will give you a slight look at the section and gasket im refering to Mercury Marine Model 1150 115 HP, 115 EXHAUST EXTENSION PLATE Parts In looking at this set up I don,t see the housing but the gromet could be affected worn dried out etc.

 

[1979checkmate]

Re: mercury tower of power cooling

Many thanks!

When i re-seated the water pickup tube (tapped it in gently using a small mallet), it felt like it made a good tight seal in a soft bushing. But hopefully within a few months a water pressure gauge will be installed to confirm.

 

[Maxz695]

Re: mercury tower of power cooling

Good to hear a nice tight fit is a good sign Best of luck scincerely Maxz 695