5.0MPI overheating help

[kharring422]

I have a sea ray 220 sundeck that has been great until last week. Out of the blue, the temp alarm went off. Guage was just over 180. We shut down and worked the boat back home. Over several days we have replaced the raw water impeller, didn't help. Replaced the entire raw pump, still no help. Pulled the thermostat, replaced the water pump on the engine flushed every hose I can find, pulled the Starbird riser and the riser and manifold looked like they were recently replaced. I pulled the water inlet from the transom and verfied I had good flow from the transom down to the water pickup and am now at a loss.
I have tried this with the prop in the water as well as with a hose connected and the results are always the same. idle\ing, the engine temp will come up to 135-150 hold there for a while (3-5 min) and then all of a sudden the temp spikes up. When this happens, it appears the engine block is empty. Risers remain cool and don't feel overly hot. I am now thinking a hose may be collapsing but the red hose that goes between the transom and raw water pump feels very firm.

 

[Espos4]

What year is the boat?
How many hours?
How long have you owned it?
Do you have water pressure readings at various rpm that you can report?

Was the impeller missing any pieces when you removed it for replacement?

Do you get sufficient volume from the water pump? There is a test to perform to verify that. A google search can help you find the specs.

 

[kharring422]

What year is the boat? 2006
How many hours? 254
How long have you owned it? 3 months
Do you have water pressure readings at various rpm that you can report? I do not. I need to pick up a gauge and monitor at different RPMs

Was the impeller missing any pieces when you removed it for replacement? Impeller was intact but there was scoring or wear marks on the end of the housing and I could feel a wear mark in the body of the impeller housing.

Do you get sufficient volume from the water pump? There is a test to perform to verify that. A google search can help you find the specs.

What year is the boat? 2006
How many hours? 254
How long have you owned it? 3 months
Do you have water pressure readings at various rpm that you can report? I do not. I need to pick up a gauge and monitor at different RPMs

Was the impeller missing any pieces when you removed it for replacement? Impeller was intact but there was scoring or wear marks on the end of the housing and I could feel a wear mark in the body of the impeller housing.

Do you get sufficient volume from the water pump? There is a test to perform to verify that. A google search can help you find the specs.[/QUOTE]

I have seen a test where you run the engine for 15 seconds and measure the volume of water that i have not tried yet because I need to pick up some hose.

 

[Espos4]

Being a 2006, dies it have smartcraft?
If so, you should be able to toggle through the settings and read your water pressure.

 

[Hoplite808]

When you replaced the impeller was the old one mangled? If it was it could be pieces of the old impeller have gone into the system and created a blockage for the coolant. The only other thing I can think of since you say everything seems okay other than the gauge suddenly going up are you sure that the sender isn’t malfunctioning?

 

[mrsrobinson]

I was thinking a collapsing hose as well.

What does engine block is empty mean? I would put the temp lazer gun on various points around the engine and see if the temps are consistent. May just be a bad sensor.

 

[dwna1a]

Forgive me, if you have a strainer, is it clean, is the scooper clean, and is the seacock all the way open?

If it is an I/O. Be sure to check the flow while off the muffs. It does make a difference.

You said the pump is scored, did you check the shaft and pulley for play. Bearings do fail and the shaft will have play. Causing a crappy pump flow.

Backflow the system

 

[Wanderer 290]

Diagnosis of the problem is essential so start with trouble shooting .
While the boat is in the water Disconnect hose(s) and check for water flow at;
1. Inlet side of raw water pump
2. Inlet side of engine water pump
3. Outlet of hose to bottom of each of the exhaust manifolds.
The goal is to find follow the flow of cooling water and verifying flow at each and every possible connection until a restricted flow is found. If no restrictions are found verify indicated temps with a infrared temp reader.

 

[kharring422]

When you replaced the impeller was the old one mangled? If it was it could be pieces of the old impeller have gone into the system and created a blockage for the coolant. The only other thing I can think of since you say everything seems okay other than the gauge suddenly going up are you sure that the sender isn’t malfunctioning?

The Impeller looked like new, but the end plates in the pump were worn and it felt like there was wear in the body, so I replaced the whole pump assembly.

 

[kharring422]

I was thinking a collapsing hose as well.

What does engine block is empty mean? I would put the temp lazer gun on various points around the engine and see if the temps are consistent. May just be a bad sensor.

When the temp gauge spikes from around 140 to 180, I shut off the engine and opened the drain plug at the thermostat and find no water in the thermostat. This has been the case every time I have checked it when the temp went up. It would idle in the water holding steady for 10-15 minutes and then suddenly rise to 180, initiate the alarm and at that point, I shut it down to avoid any damage.
I changed the sensor and sender on the thermostat housing thinking the same thing until I noticed the housing empty when it overheats.

 

[kharring422]

Diagnosis of the problem is essential so start with trouble shooting .
While the boat is in the water Disconnect hose(s) and check for water flow at;
1. Inlet side of raw water pump
2. Inlet side of engine water pump
3. Outlet of hose to bottom of each of the exhaust manifolds.
The goal is to find follow the flow of cooling water and verifying flow at each and every possible connection until a restricted flow is found. If no restrictions are found verify indicated temps with a infrared temp reader.

I have checked some but am going to go through all today as you mention to see if I can find anything as well as inspect some of the hoses I have not gotten to yet due to location to see if they are soft and could be collapsing.

 

[mrsrobinson]

This is an interesting one. Well you know you have no raw water at the thermostat, I guess start working your way back to see where you do have water.

 

[Wanderer 290]

The hose from the transom plate to the raw water pump should be rather rigid with wire re enforcement. I have never seen one of those collapse.

I did experience a problem similar to what you describe in a pick up with a small block Chevy and turned out to be the engine water pump. The impeller had separated from the shaft.

 

[Thornton69]

Your exhaust manifolds staying cool, indicate a positive raw water flow.
I would be concerned with why it is not making it through the engine block or if air is somehow being introduced into it.
Can you post the engine serial number and maybe a few pics from different angles from far enough back that we can get a good idea of what cooling package you have on it?

 

[Wanderer 290]

Your exhaust manifolds staying cool, indicate a positive raw water flow.
I would be concerned with why it is not making it through the engine block or if air is somehow being introduced into it.
Can you post the engine serial number and maybe a few pics from different angles from far enough back that we can get a good idea of what cooling package you have on it?

Certainly a possible thermostat problem… I believe a thermostat stuck closed would allow raw water to continue to flow to the manifolds and bypass the block.

 

[dwna1a]

The Impeller looked like new, but the end plates in the pump were worn and it felt like there was wear in the body, so I replaced the whole pump assembly.

You replaced the whole pump, correct? If so are the hoses back on correctly? Also did you run the new pump without water for even a minute after replacing it?

 

[Fill Ess]

Can you post pics of the engine? We need to see your setup.

Without seeing your thermostat housing, if it's the same as the ones on my 5.0 MPIs, a stuck thermostat would cause an overheat situation but you should have water at the thermostat housing drain. The water would only flow out of the smaller hoses when the thermostat is open.

 

[Bill Curtis]

My vote would be thermostat. If you are getting good flow from the raw water pump (as seen as good flow out the exhaust and cool to touch risers), the only other possible offenders are:
1. Restricted flow somewhere
2. Engine coolant circulating pump (have seen them fail by impeller coming loose from shaft or wrong pump / impeller installed)
3. Thermostat. Stat can be stuck / faulty (easily tested in pan of water on stove), can be installed backwards, or the plastic insert in the housing is not installed / indexed properly and blocks the water ports in stat housing.

One note, due to the design, the stat can be installed upside down when re-assembled. Temp sensor "pill' on stat should be facing toward the engine block, not the housing.

Another note, the stat should have a small hole in the flat "plate" to allow venting air out of engine block to the discharge. Have seen some that had the hole missing and caused what you are describing, air bounding the block and the stat won't react to air like it does to water.

 

[James Lee]

this is a great thread, lots of great problem solving suggestions. I'm having a similar issue with my 5.0 mpi on my 2005 290 Amberjack. Similar as described by Kharring. At the end of last season out of no where my smart alarm for overheating would go off. I replaced the impeller, no fix, replaced the t-stat, no fix, back flushed all hoses that I could get to, This seemed to fix it as I ran it for about 2 weeks at end of season with no alarms. I just put the boat in the water last weekend for this year and on way to dock Alarm went off again. At idle, it appears to be running about 145 but when over 3000rpm it will spike to 180 setting off alarm. Did you ever get a fix Kharring? When I changed the impeller I was in pretty bad shape some pieces were missing, so I am thinking I may have a blockage but I backflushed what I could. no fix. Where would these pieces most likely end up?? I also noticed heavy scoring on the inside of pump? When put back together I have no leaks etc. But, could this scoring cause the pump to malfunction. As an experiment, an expensive one I've ordered a new Harden sea pump and will install it this weekend. I'm hoping this does the trick. If not, at least I know I have a new pump lol. Any thoughts or suggestions appreciated. thanks

 

[Lazy Daze]

James, if the scoring on the inside of the housing/plates is enough to even just barely get your fingernail caught in them... it's too much. It doesn't take much.