Over heating 4.3, 1995 non vortec

[tumbel]

Hello everyone,
Ive run into quite a head scratcher. I have a 1995 , 4.3. Engine was rebuilt and has approximately 3 hours on it. It’s currently at the marine shop so i dont have it to look at. I sent it to the shop to have the timing set correctly and see why it was running hotter than it should be. Shop put it in time and cleaned the carb but now the alarm is going off and it’s running even hotter. They state the starboard side of the motor is letting the water out of the manifolds way too fast and not giving the engine time to cool. Water pump is working good, they checked the poppit and thermostat, verified Temperature was accurate and state they checked the manifolds. They have had my boat for 3 weeks now and want to tear off the head to see if the wrong gasket was used. Im doubtful this is the reason because the other side would be having the same issue. I asked about the flapper And they said thats only to keep water from coming back into the motor. Had anyone seen a situation like this ? When i got the boat one manifold had a small crack in it. My brother jb welded it but i don’t know if thats even on the same side as the issue.

 

[Griff Thomasson]

I have the same engine and see my post .
Do you have the 4 port or 6 port thermostat housing ?

 

[poconojoe]

Dumb question....
Was the impeller changed in the outdrive?

Sometimes a past overheat can cause an exhaust shutter (flapper) to fall down into the wye pipe and cause a blockage. I found one all the way down in my outdrive when replacing the impeller.

Also, if an impeller got destroyed in the past, rubber pieces can travel through the cooling system and cause a blockage.

I've read here that one exhaust manifold usually runs a bit hotter than the other.

Are you confirming that the engine is actually overheating? Don't trust the temperature gauge at the helm.

 

[dubs283]

I don't get it, this is a fresh rebuild and it's going back to the shop to check/adjust timing?

Not sure how an exhaust manifold can allow water out too fast. There needs to be a constant supply of fresh cooling water from the sea water pump to the t-stat housing, water is allowed out via the upper side barbs to the manifolds and possibly to the risers but the lower portion above the t-stat allows water to go to the circ pump to circulate through the block. Possibly the housing is blocked to not allow water to the circ pump but does exit to the manifold/risers.

Based on what you are saying the shop that has your boat isn't troubleshooting correctly

 

[tumbel]

I don't get it, this is a fresh rebuild and it's going back to the shop to check/adjust timing?

Not sure how an exhaust manifold can allow water out too fast. There needs to be a constant supply of fresh cooling water from the sea water pump to the t-stat housing, water is allowed out via the upper side barbs to the manifolds and possibly to the risers but the lower portion above the t-stat allows water to go to the circ pump to circulate through the block. Possibly the housing is blocked to not allow water to the circ pump but does exit to the manifold/risers.

Based on what you are saying the shop that has your boat isn't troubleshooting correctly

Idk Im questioning everything at this point. The guy at the marina said the side thats heating up is putting out alot of water. The other side only kinda spits out water. He said the side that just spits water a little at a time was the way it’s supposed to work. He said if runs straight thru it dont give the engine a chance to cool. This shop didn’t do the rebuild. I bought the engine as a short block. The engine that was bad was a 2004. I transferred all the front drive pulleys frim it to this motor. Now im wondering if i could of put the belt on incorrectly and the water pump is spinning the wrong way. Or possibly the spacer gasket is in backwards with the large hole in the front.
Thanks for checking out my post. I seriously dont think this is a head gasket issue.

 

[tumbel]

Dumb question....
Was the impeller changed in the outdrive?

Sometimes a past overheat can cause an exhaust shutter (flapper) to fall down into the wye pipe and cause a blockage. I found one all the way down in my outdrive when replacing the impeller.

Also, if an impeller got destroyed in the past, rubber pieces can travel through the cooling system and cause a blockage.

I've read here that one exhaust manifold usually runs a bit hotter than the other.

Are you confirming that the engine is actually overheating? Don't trust the temperature gauge at the helm.

Hi joe!
Yes i made sure i told them i wanted them to actually very that it was indeed over heating. So they screwed in a mechanical guage to verify. I asked about the wye pipe and they said it looks good. They also said that would not cause the water to discharge so rapidly.

 

[tumbel]

I have the same engine and see my post .
Do you have the 4 port or 6 port thermostat housing ?

Hi joe!
Yes i made sure i told them i wanted them to actually very that it was indeed over heating. So they screwed in a mechanical guage to verify. I asked about the wye pipe and they said it looks good. They also said that would not cause the water to discharge so rapidly.

Forgot this part. No impeller was not changed due to the fact engine is getting lots of water intake.

 

[achris]

....They state the starboard side of the motor is letting the water out of the manifolds way too fast and not giving the engine time to cool. ..

This thing about water going to fast to cool is the biggest load of tripe I have ever heard. It's complete bunkum, and it's always trotted out by morons who haven't got a clue what they're doing and want to sound smart. It's complete BS!

One of the things we proper mechanics check for is that the manifolds and elbows are completely free to flow water as easily as possible. If there's any blockage in them, engines overheat!

Chris...
(A proper mechanic)

 

[tumbel]

This thing about water going to fast to cool is the biggest load of tripe I have ever heard. It's complete bunkum, and it's always trotted out by morons who haven't got a clue what they're doing and want to sound smart. It's complete BS!

One of the things we proper mechanics check for is that the manifolds and elbows are completely free to flow water as easily as possible. If there's any blockage in them, engines overheat!

Chris...
(A proper mechanic)

 

[tumbel]

Hi chris,
Thanks for your advice. Im so lost on this it ain’t funny. I know just enough to be dangerous. They were supposed to have switched out the elbow and riser to test it. Only going by what they said they did. I just don’t believe the problem is in the head gasket. Mechanic states. I’ve seen guys rebuild these motors and use automotive ones and they end up blocking off water jackets”. Now if thats the case it would be both sides getting hot. Just my opinion.

 

[Scott Danforth]

This thing about water going to fast to cool is the biggest load of tripe I have ever heard. It's complete bunkum, and it's always trotted out by morons who haven't got a clue what they're doing and want to sound smart. It's complete BS!

it applies to a thermostat in the sytem. if there is no thermostat in an engine, the water velocity is too fast to adequately transfer heat from the hot surface to the fluid. if you do not run a thermostat, you do need to run an orifice disc

 

[achris]

.... Mechanic states. I’ve seen guys rebuild these motors and use automotive ones and they end up blocking off water jackets”. Now if thats the case it would be both sides getting hot. Just my opinion.

If they used the wrong gasket on one side, you'd get overheating only on that side. And yes it's possible someone did use one right gasket and one wrong gasket...

 

[achris]

it applies to a thermostat in the sytem. if there is no thermostat in an engine, the water velocity is too fast to adequately transfer heat from the hot surface to the fluid. if you do not run a thermostat, you do need to run an orifice disc

In these engines you will get an overheat from not using a thermostat, but it has nothing to do with the water velocity, and everything to do with flow paths... Without the thermostat there's nothing to force the cool incoming water into the engine block (and heads), it just flows straight through to the manifolds/elbows and out. The water in the block is never replaced and gets hotter and hotter... Equals overheat...

If the removal of the thermostat caused the water to move too fast, every car without a thermostat would overheat yet they don't, they run too cold!

 

[tumbel]

I have the same engine and see my post .
Do you have the 4 port or 6 port thermostat housing ?

Griff , i saw the post but was having a little trouble following it. I have 6 hoses to the top of the motor. 2 run to the popit, 2 to the elbows, an inlet and outlet I believe. They said they checked the popit valve and everything looked straight.

 

[dubs283]

I transferred all the front drive pulleys frim it to this motor. Now im wondering if i could of put the belt on incorrectly and the water pump is spinning the wrong way.

Did you do just the pulleys and not the circ pump? Reason I ask is if your original motor (2004?) had a serpentine belt and the donor motor had a v-belt system the donor motor could have a unidirectional circ pump while the serpentine belt one had a bidirectional pump. New replacement circ pumps are bidirectional but if the donor motor is old enough it could be unidirectional. Just a thought...

 

[Scott Danforth]

If the removal of the thermostat caused the water to move too fast, every car without a thermostat would overheat yet they don't, they run too cold!

Under load, they overheat. A car engine only produces full load 3-5% of the time as you cant get to a higher duty cycle. Run the engine PTO or in a drag race situation to get to 100% duty cycle and you overheat

 

[Griff Thomasson]

Griff , i saw the post but was having a little trouble following it. I have 6 hoses to the top of the motor. 2 run to the popit, 2 to the elbows, an inlet and outlet I believe. They said they checked the popit valve and everything looked straight.

I would recheck that as those balls need to be up tight against the housing and open only at high speed

 

[Rick Stephens]

Idk Im questioning everything at this point. The guy at the marina said the side thats heating up is putting out alot of water. The other side only kinda spits out water. He said the side that just spits water a little at a time was the way it’s supposed to work. He said if runs straight thru it dont give the engine a chance to cool. This shop didn’t do the rebuild. I bought the engine as a short block. The engine that was bad was a 2004. I transferred all the front drive pulleys frim it to this motor. Now im wondering if i could of put the belt on incorrectly and the water pump is spinning the wrong way. Or possibly the spacer gasket is in backwards with the large hole in the front.
Thanks for checking out my post. I seriously dont think this is a head gasket issue.

What kind of exhaust have you? Factory 'out the drive with idle relief ports'?

Rick

 

[tumbel]

Did you do just the pulleys and not the circ pump? Reason I ask is if your original motor (2004?) had a serpentine belt and the donor motor had a v-belt system the donor motor could have a unidirectional circ pump while the serpentine belt one had a bidirectional pump. New replacement circ pumps are bidirectional but if the donor motor is old enough it could be unidirectional. Just a thought...

Hmm. I never thought of that. Ill let the marina know. I believe the motor is a 94. I know its non vortec

 

[tumbel]

What kind of exhaust have you? Factory 'out the drive with idle relief ports'?

Rick

Rick. Id love to give you an answer to that question but idk what your talking about. Just a regular mercruiser 4.3 manifold to a 4” riser and then to the exhaust elbow. Im new to this owning a boat thing.