Overheating

[Intruder 4.3]

Hey guys,
I have a 2004 Mercruiser 4.3L MPI (Engine serial number OWOO7177 - model -MCM4.3L MPI) Alpha drive (Drive serial number OL9566Z3) with a closed cooling system installed in a 2004 20' Alumaweld Intruder. Took it out from winter storage today and had the alarm indicator whistling at me. I believe it was over heating and as far as I can tell, the sea water pump is not pumping water through the system.
Once I had it home I hooked up the hose to the muff, and ran the water. The water was not coming out of the out drive. I have 2 Blue drain plugs on the sea water pump. One is for the intake side and the other is for the after pump side. Under garden hose pressure I was getting water out of both of them.

My questions are:
1. What other tests can I perform to isolate this symptom to the sea water pump?
2. If I can determine the pump is in fact the problem, can this pump be rebuilt, if so where can I buy a rebuild kit?
3. Where should the water be exiting the system on my drive? I am thinking through the center of the prop along with the exhaust.
4. When a through hull pump is installed does the out drive impeller still pump water?
5. Am I asking the right questions above?

I did search for this, if this has already been covered I apologize, please post a link.

Any input is helpful
Let me know if additional information is needed.

Thanks!
Chad

 

[telstar1]

Re: Overheating

Need to know if you have a thru hull pump.I gather you do because you refer to the intake side of the pump. There is no such place on a regular alpha "in the drive" water pump.If you hooked up water to muffs and got water "to the pump"Im thinking you have some setup where water is drawn up thru the drive to your pump?
Or are you referring to the water circulating (automotive)pump on front of engine?If you are, and flow is as you say, you do not have closed cooling.(is there a rad cap anywhere?if not you DONT have closed cooling.Need the answers to go further.
Water will exit thru ports either side of gimbal housing and out thru prop,if you are pumping seawater properly..

 

[Intruder 4.3]

Re: Overheating

Need to know if you have a thru hull pump.I gather you do because you refer to the intake side of the pump. There is no such place on a regular alpha "in the drive" water pump.If you hooked up water to muffs and got water "to the pump"Im thinking you have some setup where water is drawn up thru the drive to your pump?
Or are you referring to the water circulating (automotive)pump on front of engine?If you are, and flow is as you say, you do not have closed cooling.(is there a rad cap anywhere?if not you DONT have closed cooling.Need the answers to go further.
Water will exit thru ports either side of gimbal housing and out thru prop,if you are pumping seawater properly..

Telstar1,
Yes, I have a through hull pump. The intake comes through the hull to a petcock valve (which is in the open position) and then to a belt driven pump. The sea water comes in the upper side and exits through the lower. This pump is located on the lower starboard side of the engine.
Definitely do have a closed cooling system which has the single point air actuated drain.
Yes there is a radiator cap on the heat exchanger.
I thought my reference to "muff" would be misleading, as I have a toilet plunger cup looking muff (singular) that presses up against the bottom of the hull covering the intake.

Thanks,
Chad

 

[Intruder 4.3]

Re: Overheating

Well this kind of works. Here are some pictures.
http://www.facebook.com/album.php?fbid=1756748990775&id=1000479101&aid=97437

 

[telstar1]

Re: Overheating

Cant quite know where youre at with test but if no water comes out thats a problem. Id look at impellor(whip the cover off pump youll see it) and anythimg that looks like a strainer which could very well be plugged. Basically start at one end and keep tracing water by disconnecting hoses till you find the blockage or lack of pumpability.Exhaust risers,right at the tail end of the system,are prone to clogging and will prevent the flow of water no matter what shape everything else is in.Youll know thats the problem if you disconnect hoses just ahead of them and get good flow. Note you may have a half system where ex.manifolds AND risers are raw water cooled or you may have a full system where only risers are raw water cooled. Hose routing and a bit of thought will tell you which you have. We need to know that too.

 

[Intruder 4.3]

Re: Overheating

Ok I pulled the pump and split the case. Sure enough the impeller was toast. Apparently when flushing this type of system with a through hull intake you must supply water to both the outdrive and the through hull intake. I have flushed this system twice since I bought it. So now I get to drop the lower unit and replace the stern drive impeller as well. No big deal as I do not think either as ever been replaced. This seems like an engineering oversight. I think I will just run to the river to flush from here on out.

http://www.facebook.com/album.php?id=1000479101&aid=97554

 

[telstar1]

Re: Overheating

Your system beyond my knowledge.Cant do facebook. What pray tell does the pump in the drive do?

 

[Intruder 4.3]

Re: Overheating

The dealer ship service guy told me that the drive impeller does run and is cooling the lower unit oil. However they close the ports to the engine, so it is a separate loop just for the lower unit oil. I will see if I can host these pictures somewhere else, and post a link.

 

[Don S]

Re: Overheating

You probably need a new impeller, they are a maintenance item.
Rule of thumb, replace the impeller every other year. Since you are asking if it can be rebuilt, I would have to assume the impeller has been in the pump since 2004. Way too long for those type impellers.

 

[CharlieB]

Re: Overheating

Looked at the pictures, two things come to mind.

First, where are the rest of the pieces of the old impeller, they need to be found and removed as they will restrict water flow.

Second, scoring of the pump cover. If not already, this will soon begin to reduce sealing of the impeller, this cover can be refinished, I would recommend replacement, then refinish this one and save it along with a spare impeller to take along for any on-the-water emergent repair/replacement.

 

[Intruder 4.3]

Re: Overheating

Ok so I changed the Impeller in the sea water pump. I then hooked it up the Muff (Single) for the through hull pick up to check and see if water was making it all the way through the system . Of course it was not.SO now I went looking for the pieces of impeller. I began by flushing fresh water through the manifold that cools the power steering fluid backwards, flowed right through with no blockage. I then pulled the exhaust manifold riser on the port side, to clean out the ports, as I have read that this is a common place to be plugged. No clog was found in the port side riser so I put it back together with a new gasket plate (can these be reused?). Once I had this riser back together and bolted down tight, I ran the garden hose directly to the hose bib on the riser to see if water would flow out the out drive. It did but the water was white! I apparently was flushing all of my engine antifreeze out the Gimbel port on the out drive (port side only). How can this be? Bad seal on the gasket plate of the riser I disassembled? SO then I went to refill the heat exchanger with water at the rad cap, and the water went straight out the same Gimbel port on the out drive! How is this possible, and How do I fix this?

Thanks!

Update: pulled the riser back off and found that the parts guy sold me a gasket for an open cooling system...Mystery solved.