Still overheating on the water but not in the driveway.

[jdogonhood]

So after replacing the raw water pump on my 4.3 OMC Cobra took it to the lake and it still overheated. Ideas? Runs super cool in the driveway so flow must be good. Those chevy water pumps work unless spitting water out of the relief hole right? Could it be the problem.? Where are my OMC PEEPS. Please help running out of excuses for the wife why we should keep it.

 

[lesismore]

Re: Still overheating on the water but not in the driveway.

Check out if the impeller will turn on the shaft before putting the case over it. It shouldn't. Be sure the shaft is turning by having someone turn engine over for a second while you hold on to the impeller to put a little pressure on it to be sure it is not slipping. Our 1990 4.3 OMC has a shorter shaft and we have to cut out the closed end and mount it backwards. It had the same symptoms. The marina didn't even know about this issue. Also be sure impeller is set to turn in the right direction with the fins trailing the direction it turns. FYI we put the propeller in a large container filled with water and it overheated in the driveway. The impeller will not pull water up into the pump. It sits at prox the waterline in the water and is not designed to suck water all the way up from the intake.

 

[Gettinther]

Re: Still overheating on the water but not in the driveway.

So after replacing the raw water pump on my 4.3 OMC Cobra took it to the lake and it still overheated. Ideas? Runs super cool in the driveway so flow must be good. Those chevy water pumps work unless spitting water out of the relief hole right? Could it be the problem.? Where are my OMC PEEPS. Please help running out of excuses for the wife why we should keep it.

In the drive way your water supply has pressure so the water is pushed through, on the lake the raw water pump has to pull the water in as well as push it through to the engine, so i would look for blockage or test to see if the raw water pump is working well enough.
Here is a water flow chart from older drives but might be close enough to give a good idea. This is also likely an imperial gallon measurement or 160 fluid ounces

Good luck with wife and boat

 

[jdogonhood]

Re: Still overheating on the water but not in the driveway.

Sweet. Thank you. I will try this in the morning...

 

[jdogonhood]

Re: Still overheating on the water but not in the driveway.

So I took it apart today and turned it over to first make sure it turns and it does. I grabbed it while it was turning and it did not slip. I dropped the out-drive in a large container and ran the motor then disconnected the hose @ the thermostat housing to check for water flow and there was nothing. So I then checked for possible blockage and found none. Water flows great with the pressure from the hose..... So What next? Seems like the impeller just is not working but it should because it is new and is turning. Could it be the water pump on the motor that works in connection to cause the water to pump? What am I missing? Is it correct that the impeller does not pump enough water to even get a little flow up to the intake? Now I am really confused. Do I really have to take it in.......?

 

[jdogonhood]

Re: Still overheating on the water but not in the driveway.

I am getting no water flow with the new impeller. I placed the out-drive in a large container and ran the motor then disconnected the hose @ the intake and nothing....With the hose water flows through fine. What am I missing? The impeller is turning fine even when I grab and squeeze it and it does not slip. So I'm very confused now because it should be pushing water...

 

[jdogonhood]

Re: Still overheating on the water but not in the driveway.

So is it the water pump on the engine that is bad if the impeller is turning fine?

 

[sea wolf]

Re: Still overheating on the water but not in the driveway.

I am getting no water flow with the new impeller. I placed the out-drive in a large container and ran the motor then disconnected the hose @ the intake and nothing....With the hose water flows through fine. What am I missing? The impeller is turning fine even when I grab and squeeze it and it does not slip. So I'm very confused now because it should be pushing water...

Forget about submerging the drive in a container, the impeller housing must be submerged. Check the o-ring gasket in the impeller housing. If it moved out of the groove the pump will suck air. Before installing the impeller housing, bump the engine so the narrow end of the water pump shaft is facing downward. Twist the impeller so that the narrow pocket is also facing downward. That way u won't have to twist the housing when installing it onto the shaft. If u do it that way, the seal will stay in the groove.

 

[jdogonhood]

Re: Still overheating on the water but not in the driveway.

What direction is the impeller supposed to turn when looking @ it from the back while someone else turns the motor over? Mine turns counter-clockwise. Did I put the wrong rotating motor in when I switched blocks? Help.

 

[Idlespeedonly]

Re: Still overheating on the water but not in the driveway.

Counterclockwise is correct

 

[trihull59]

Re: Still overheating on the water but not in the driveway.

Take the thermostat out of the thermostat housing and then put everything back together then see if it overheats. Sometimes the thermostat can become stuck shut causing no water flow through the manifold and head causing it to overheat.

 

[offshore79]

Re: Still overheating on the water but not in the driveway.

I just got through all this. Read this thread.
http://forums.iboats.com/showthread.php?t=508813

 

[HCMQA]

Re: Still overheating on the water but not in the driveway.

taking the tstat out will not help at all even if it is stuck.
he is not getting any water to the stat and there is a by pass to the risers when the stat is closed.

he is most likely sucking air

 

[jdogonhood]

Re: Still overheating on the water but not in the driveway.

so I dropped the lower unit and found the rubber grommets and guide to be melted around the water tube and was sure this was the problem. took it to the lake and it still overheated. Pulled the raw water hose and there was no continuous water flow it just spitted a little water @ idle, and it seemed as though hot water and air were also being spitted out from the t-stat housing instead of sucking. Is this right? In the driveway with the hose we get good flow from the inlet to the t-stat but not on the lake. Replaced the raw water pump and now rubber and guide on water hose. Checked the t-stat and it opens @ 160 degrees and closes @ 158 degrees. Haven't replaced the engine water pump yet but it doesn't seem like the prob cause there is no water flow to the t-stat housing on the lake. What am I missing?

 

[ljsweeney]

Re: Still overheating on the water but not in the driveway.

I just had this issue fixed on my boat.

I replaced the seals at both ends of the water tube as well as the guide, and I could not get good water flow to the 'stat housing.

I finally threw my hands up and took it in to the shop. They could not find anything that looked bad, so they replaced the o-rings and seals in the lower unit. That did the trick, and she is running fine now.

FYI, my lower was connected to an upper that overheated and fried the main carrier bearings. The heat must have cooked the seals in the lower to the point that they did not function. Since you see evidence of high temps in your water channel, I would be willing to guess that resealing the lower would resolve your issues as well.

Good luck.

 

[HCMQA]

Re: Still overheating on the water but not in the driveway.

jsweeney is prolly correct

the tstat housing is going to spit at you if it is dry and hot from a running engine. it is not going to suck in if there is no water to suck in.

if all else has been checked and verified(impeller spinning, pump housing sealed properly, no obstructions etc..) it sounds like you may need a seal job.