Over heating 1988 mercruiser 185 4.3

[Cpalmer88]

This is the cooling sytem. I just replaced the thermostat (yes with correct marine one) and impeller. While testing I have it in a bucket that way water is not being shoved by hose. I'm getting plenty of water flow. I opened individual lines while running it and every line is getting water. The exhaust is pumping out water. I'm kind-of at a loss. Time to move on to you experts on troubleshooting. Also is there a service manual with raw water cooling system in it? I can only find them with closed systems. If this isn't posted in the correct place sorry first post

 

[nola mike]

What's your serial #? An '88 should be Merc manual #7. Your diagram doesn't look right...
Was it overheating prior to your work?
Try running it on muffs and not in a bucket, and verify your temps with an IR gun.
This is the correct area to post.

 

[Cpalmer88]

What's your serial #? An '88 should be Merc manual #7. Your diagram doesn't look right...
Was it overheating prior to your work?
Try running it on muffs and not in a bucket, and verify your temps with an IR gun.
This is the correct area to post.
View attachment 380714

Yes it was overheating prior. Inherited this project was hoping it was just the impeller. I will grab my ir from work tomorrow and report back that the temp is correct. Your diagram is exactly it. The one I posted was just the closest I could find. S/N on the valve cover is B521565.

 

[nola mike]

Which diagram? There are 2 I posted

 

[Cpalmer88]

Which diagram? There are 2 I posted

Sorry, top one. Here is actual photos of it

 

[dubs283]

Based on pictures and your confirmation of the cooling system there should be no check balls in the t fitting supplying water to the exhaust risers/elbows. Your description of the overheat sounds exactly like a cooling system with the check balls. Only way to know is remove the hoses at the t fitting and verify

Running out of the water you should be using muffs, buckets are okay but don't give an accurate representation of the boat in the water

Post back results from running on muffs and verify temps with an ir gun

 

[Cpalmer88]

There are check ball looking things in this T fitting here.

 

[dubs283]

With the check balls in place it may be the springs have lost tension and allowing the balls to not seat properly. Another problem may be the balls are worn to the point they no longer seat properly

If you remove the assy you can stretch the springs and turn the balls around so the normal, rounded sides of the balls seat properly

 

[Scott Danforth]

Attempting to suck water from a bucket will just toast your impeller.

You need a bucket big enough to float the whole boat and get the water level higher than the impeller to get it to prime

 

[Cpalmer88]

With the check balls in place it may be the springs have lost tension and allowing the balls to not seat properly. Another problem may be the balls are worn to the point they no longer seat properly

If you remove the assy you can stretch the springs and turn the balls around so the normal, rounded sides of the balls seat properly

What is the purpose of the check balls? How should they operate?

 

[Cpalmer88]

Attempting to suck water from a bucket will just toast your impeller.

You need a bucket big enough to float the whole boat and get the water level higher than the impeller to get it to prime

Yea just did that way to ensure the impeller was actually doing its job and not the pressure of the hose... back to muffs to ensure I don't burn up the impeller.

 

[nola mike]

What is the purpose of the check balls? How should they operate?

They should be snug against the outlet. They prevent the water from just dumping out the elbows (without going through the engine) at low rpms. Higher rpms/higher water pressure opens the balls and then lets more go out the elbows.

 

[Cpalmer88]

They should be snug against the outlet. They prevent the water from just dumping out the elbows (without going through the engine) at low rpms. Higher rpms/higher water pressure opens the balls and then lets more go out the elbows.

Well that's one issue because they are sloppy.headed home now to toy with it

 

[Scott Danforth]

Yea just did that way to ensure the impeller was actually doing its job and not the pressure of the hose... back to muffs to ensure I don't burn up the impeller.

If you attempted to run from a bucket, that impeller was run dry.

 

[Cpalmer88]

Well that's one issue because they are sloppy.headed home now to toy with it

So far idle for about 10 min.... gauge reads 150 ish. Ir on thermostat housing is 156

 

[Cpalmer88]

If you attempted to run from a bucket, that impeller was run dry.

I don't see how. It was completely submerged and had continuous was running it. And it's still pumping water through the engine

 

[Cpalmer88]

They should be snug against the outlet. They prevent the water from just dumping out the elbows (without going through the engine) at low rpms. Higher rpms/higher water pressure opens the balls and then lets more go out the elbows.

Been runn8ng for some time gauge reads 150ish thermostat housing reads 157 and holding. The hoses coming from the T with check balls are cold. Maybe they need replaced? I stretched the springs to make them more stiff but they still are not very stiff

 

[Scott06]

Been runn8ng for some time gauge reads 150ish thermostat housing reads 157 and holding. The hoses coming from the T with check balls are cold. Maybe they need replaced? I stretched the springs to make them more stiff but they still are not very stiff

Those hoses should be cold. They let a constant flow of raw water through to cool the exhaust regardless of if the thermostat is open or closed

if they let too much water by the engine gets starved of incoming water and will over heat

 

[Cpalmer88]

Okay been a while of sitting here. Muffs are on water comes from a very cold well. Front of head running 167-170. Top thermostat is 129 bottom is 157. Still on the hot side. What else do I need to look at

 

[nola mike]

Okay been a while of sitting here. Muffs are on water comes from a very cold well. Front of head running 167-170. Top thermostat is 129 bottom is 157. Still on the hot side. What else do I need to look at

So did you get the check balls snugged?