1985 150 merc. Cooling system question.

[inkercg]

I recently just bought my first bass boat. 1985 Skeeter Starfire 150 with a mercury 150. serial # A114196. Had an alarm go off the first trip out. To make a long story short i replaced the temp sensor located below #1 cylinder, also installed a water pump and put thermostats in. still had an alarm go off any time i was on plane as soon as i back out of the throttle it quit. I noticed that it was still not peeing vary good at idle and low rpm. I checked the compression to see if there might be a head gasket problem. (as suggested by a mechanic.) The compression was 125psi to 130psi across the board. With no two having the same compression on the same side. The next thing i did was remove the thermostats and now it shoots a stream of water like 6ft.

My question is: Will running without thermostats cause a problem. and why do they even put thermostats on these motors. Might be a dumb question but i guess in my mind if there is no restriction than it will always be bringing fresh water through the motor to keep it cool.

 

[Dukedog]

Re: 1985 150 merc. Cooling system question.

It has to have some restriction (t-stats in your case) to keep tha water in tha block long enough to cool tha motor. Water runnin' straight through will not dissapate tha heat like a lot of folks think. Even it does tha motor would not perform like it should. Tha water around tha clyinders has to heat up as tha clyinder heats up. Heat = horsepower/proper performance. Runnin' a cold motor can cause really bad things.

If you know tha pump and stats or workin' right, replace tha popet assy. and get a water pressure guage. It can become your best friend. If its still acts up ya might have to start lookin' for a restriction somewhere in tha coolin' system.........................

 

[inkercg]

Re: 1985 150 merc. Cooling system question.

I know now after removing the thermastats that the pump is working. the thermastats that i took out r new just put them the day before and still had an alarm go off with the new ones.
What should i be looking for with a water pressure gauge? Is there a range i should stay in? (idle vs running) As for Poppet valve i dont think i have one but i could be wrong. seral # A114196.

 

[j_martin]

Re: 1985 150 merc. Cooling system question.

I know now after removing the thermastats that the pump is working. the thermastats that i took out r new just put them the day before and still had an alarm go off with the new ones.
What should i be looking for with a water pressure gauge? Is there a range i should stay in? (idle vs running) As for Poppet valve i dont think i have one but i could be wrong. seral # A114196.

That engine has several ways for water circulation to happen.

1. Some flows all the time, through open ports in the base. T-stats are necessary to establish the flow pattern needed for that or uneven warmup, and possible ugly things like cold seize can occur.

2. When the engine warms up, additional water is allowed to flow past the t-stats. That also feeds the pee stream, which tells you the engine is warm enough to blast off without the above said cold seize.

3. As engine rpm's and water pressure increase, the poppet valve allows additional water to escape.

A pressure gauge will sit at about 5 lbs at idle, increase to 12 or so at 3000 rpm, step back slightly, but noticeably when the poppet opens, and increase to 20 lbs or so at full speed. Once you get used to what it does, it's easy to pick up on things like debris in the engine plugging it up, (high at idle) to bad water pump (low most of the time).

If your engine is not in peak tune, especially timing and fuel mix at WOT, it'll be prone to overheating even if the entire cooling system is perfect.

hope it helps
John

 

[inkercg]

Re: 1985 150 merc. Cooling system question.

3. As engine rpm's and water pressure increase, the poppet valve allows additional water to escape.

Can you tell me if my Motor has a poppet valve and where it might be located. I will go ahead and reinstall the t-stats as not to create a problem. I m going to install a pressure gauge and check to make sure the rubber ring on the shaft just above the water pump housing is tight against the pump housing. Thanks for the input.

 

[j_martin]

Re: 1985 150 merc. Cooling system question.

Can you tell me if my Motor has a poppet valve and where it might be located. I will go ahead and reinstall the t-stats as not to create a problem. I m going to install a pressure gauge and check to make sure the rubber ring on the shaft just above the water pump housing is tight against the pump housing. Thanks for the input.

Yes it does. It's on the starboard side, low on the block.

When you get a pressure gauge hooked up, read it to us and then someone can tell you if you have to go into the poppet, or what else might be wrong.

BTW, it would be worthwhile to pull the plugs and peer into each cylinder. If you have one that is squeeky clean, you might have a head gasket problem. If they all have an appropriate amount of carbon, you're ok in that department.

At this point it is impossible to even scientifically guess at what the problem is. All we can know is that it runs a tad bit hot. The most likely reason if that boat is set up any near right is that yer pulling the water pickup a bit out of the lake. The pressure gauge will tell you that immediately.

Another thought just came to mind. When you put in an impeller, did you put a bead of silicone along the top of the divider between the exhaust side and the water pickup side of the foot?

The rubber ring (slinger) is no big deal. Even if it slipped up the shaft it wouldn't cause a loss of water flow. It's not a seal, it's just a slinger.

Preacher warning...........
All of this info is in the book.
All clear............

hope it helps
John

 

[inkercg]

Re: 1985 150 merc. Cooling system question.

Another thought just came to mind. When you put in an impeller, did you put a bead of silicone along the top of the divider between the exhaust side and the water pickup side of the foot?

No I did not. Is this something i should do. Is there a good place to order a water pressure gauge from.

Thank you so much.

 

[j_martin]

Re: 1985 150 merc. Cooling system question.

No I did not. Is this something i should do. Is there a good place to order a water pressure gauge from.

Thank you so much.

Like I said, it's in the book.

Without a seal there, you can get a little exhaust in the intake water, especially when running hard.

When I put mine together, I put a healthy bead of sillycone on the divider, and a real thin coat of grease on the mid where it mates, then let the sillycone skin before I bolt up. Then most of the time it'll come apart without damage and I can just slap it back together. If it has any wear and tear, it gets replaced. (new bead of glue)

I'm sure I-boats has water pressure gauges.

Hope it helps
John

 

[Chris1956]

Re: 1985 150 merc. Cooling system question.

John, I am not sure I understand the placing of the silicone, when repairing the waterpump. All the cooling water goes up the 1/2" copper water tube to the heads. The expelled cooling water falls down the midsection and exits the grates above the prop and A-V plate. Did I miss something?

 

[j_martin]

Re: 1985 150 merc. Cooling system question.

John, I am not sure I understand the placing of the silicone, when repairing the waterpump. All the cooling water goes up the 1/2" copper water tube to the heads. The expelled cooling water falls down the midsection and exits the grates above the prop and A-V plate. Did I miss something?

If you look downward at the LU, you'll see the exhaust side, and a divider plate that comes to the top surface, and the other (front)side is where the water pump is. If the seal is missing, you can get some exhaust in the suction side of the pump. Most of the exhaust goes down into the lower and out through the prop hub.

Instruction 4 for installing the LU reads, "Apply a thin bead of GE silicone sealer against the top of the divider block."

I usually use permatex blue silicone gasket maker.
Obtain the book.

hope it helps
John

 

[Dukedog]

Re: 1985 150 merc. Cooling system question.

If the seal is missing, you can get some exhaust in the suction side of the pump. Most of the exhaust goes down into the lower and out through the prop hub.

Instruction 4 for installing the LU reads, "Apply a thin bead of GE silicone sealer against the top of the divider block."

I usually use permatex blue silicone gasket maker.
Obtain the book.

hope it helps
John

?????? Guess I'm missing something. I don't even run a "can" much less any kinda seal and don't have any problem with exhaust in tha water. I tend ta burn up a lot of plastic guide tubes but thats about it..............

 

[j_martin]

Re: 1985 150 merc. Cooling system question.

?????? Guess I'm missing something. I don't even run a "can" much less any kinda seal and don't have any problem with exhaust in tha water. I tend ta burn up a lot of plastic guide tubes but thats about it..............

I guess the manufacturers don't know how to repair their own product.

I don't know for sure what the problem would be if the silicone bead is missing, because I follow instructions. I do remember that the marine mechanic that sold me my first water pump kit thought the silicone was important enough to mention the need to apply it.

At this point we still don't have basic data needed for a real good guess about what the problem would be. We'll get that when the pressure gauge is installed. This item is in the "touch all the bases" category.

hope it helps
John

 

[Dukedog]

Re: 1985 150 merc. Cooling system question.

Forgot ta ask. Did you replace tha complete water pump or just tha impeller? Was it OEM or aftermarket?

John, that seal is just to keep any exhaust and heat from gettin' into tha drive shaft side of tha downhousing so tha paint will stay nice. There is no way for it (exhaust) to get into tha water intake or pump.........................

 

[j_martin]

Re: 1985 150 merc. Cooling system question.

Forgot ta ask. Did you replace tha complete water pump or just tha impeller? Was it OEM or aftermarket?

John, that seal is just to keep any exhaust and heat from gettin' into tha drive shaft side of tha downhousing so tha paint will stay nice. There is no way for it (exhaust) to get into tha water intake or pump.........................

Good to know. Heard of it being an issue once, could have been a combination problem with a bad base gasket.

 

[alwims]

Re: 1985 150 merc. Cooling system question.

Forgot ta ask. Did you replace tha complete water pump or just tha impeller? Was it OEM or aftermarket?

John, that seal is just to keep any exhaust and heat from gettin' into tha drive shaft side of tha downhousing so tha paint will stay nice. There is no way for it (exhaust) to get into tha water intake or pump.........................

You are probably right about the exhaust not being able to get "into" the water, BUT, after reading johns post, last night, I went out and pulled my lower unit on my '85 150 hp XR2. I looked very carefully and it looked like my water pump housing was getting very hot from the exhaust gases. It was even discolored, but not melted so I sealed the plate with red high heat gasket maker and put it back together. Today I ran about 10 miles and had a very noticeably cooler running engine, about 20 degrees cooler and the water temp was 85 degrees, same as yesterday. Thanks john.

 

[trumanlake]

Re: 1985 150 merc. Cooling system question.

If I may. I read something in the 4 sentence that caught my eye. You said you replaced the temp sensor, important question, is the lead length the same on the new sensor as compared to the old one? The reason I ask is that, lead length identifies the difference between the two sensors that can be installed.
Been there done that.

 

[inkercg]

Re: 1985 150 merc. Cooling system question.

If I may. I read something in the 4 sentence that caught my eye. You said you replaced the temp sensor, important question, is the lead length the same on the new sensor as compared to the old one? The reason I ask is that, lead length identifies the difference between the two sensors that can be installed.
Been there done that.

The new one was a bit longer.

Installed water pressure gauge and took poppet off and cleaned the build up off and checked the rubber diaphram for damage. I replaced the rubber grommet and the hard plastic bushing in the block on the back side of the poppet valve.
I took the boat out for a test run tonight. water pressure at idle to 1200rpm was 15-18psi the highest i seen it get was 28psi while i was running about 45mph. I did not get an alarm. but i didnt run a vary long time.

 

[Dukedog]

Re: 1985 150 merc. Cooling system question.

I looked very carefully and it looked like my water pump housing was getting very hot from the exhaust gases. It was even discolored, but not melted so I sealed the plate with red high heat gasket maker and put it back together. Today I ran about 10 miles and had a very noticeably cooler running engine, about 20 degrees cooler and the water temp was 85 degrees, same as yesterday. Thanks john.

I donno? I've ran ever hot rod I've had since tha first V6 came out without a can and tha exhaust blowin' straight from tha tuner at tha pump and never had a problem other than tha melted guide tubes. Tha aluminum ones we use now have fixed that. But who really knows with some of thes Mercs

 

[j_martin]

Re: 1985 150 merc. Cooling system question.

The new one was a bit longer.

Installed water pressure gauge and took poppet off and cleaned the build up off and checked the rubber diaphram for damage. I replaced the rubber grommet and the hard plastic bushing in the block on the back side of the poppet valve.
I took the boat out for a test run tonight. water pressure at idle to 1200rpm was 15-18psi the highest i seen it get was 28psi while i was running about 45mph. I did not get an alarm. but i didnt run a vary long time.

Those numbers look a bit high. As you're slowly reving it up, at some speed in the midrange, the pressure should suddenly drop off a few lbs. At what rpm and pressure does that occur? (Trying to discern operation and meter calibration problems)

John

 

[inkercg]

Re: 1985 150 merc. Cooling system question.

I finally got a chance to run the boat a little more. First i Slowly revved the motor. The pressure was at 15lbs at idle and brought it up to 4000 rpm and the pressure slowly went to 25lbs and floated between 24 and 28 lbs. when i pulled off the throttle it came back down to 5 lbs, and as soon as i put it gear it came back up to 15lbs.

Back to the alarm issue. When i run 35 plus mph. the alarm will sound. when I run 30mph and hold the rpm at 3000. the alarm will not sound. When running full throttle the alarm sounds and as soon as i go back to idle for a few sec. the alarm quits. I removed all transducers and looked under the boat for any damage that might cause air bubbles to pass by the water pickups. I'm now out of ideas