It's Saturday - help me before I completely disassemble my engine

[harleyfool]

2000 Volvo 4.3 GL - PEFS - OVERHEATING

Supposed 10 years as a fresh water boat - new to me.

After about a 3 hour uneventful run hauled boat out of water (salt) and returned home. I put muffs on the drive and attempted to flush. Started boat and no water return back thru stern drive. Ultimately opened sea pump and discovered the "original impeller" had lost a fair number of teeth. Removed thermostat housing,hoses and thermostat (and replaced). Everything was very clean AND no bits of impeller. Put on muffs and restarted boat. Now the usual water return I expected thru the stern drive. But, boat overheats. Thermostat will run up to 180-185 before I shut it down. Large hose from thermostat housing to water pump is warm but everything else, including manifolds is cool.

Today I:
1. Removed and replaced all spark plugs - all were dry
2. Removed thermostat housing and all attached hoses. Probed all holes and hoses. No debris and no obstruction.
3. Removed new thermostat and placed in hot water to verify operation. It is OK.
4. Loosened belts and removed pulley on water pump. Spun it by hand and could hear water sloshing and would get some return back thru top of block where thermostat housing sits.
5. Jammed garden hose down end of large hose previously attached to thermostat housing - thus running back thru water pump, thru block and out thru top of block where thermostat housing sits. Good water return noted.

Frustrated. Any advice.

 

[caver95]

Re: It's Saturday - help me before I completely disassemble my engine

I dont think 180-185 is overheating. but I could be wrong.

 

[harleyfool]

Re: It's Saturday - help me before I completely disassemble my engine

Before the impeller disintegrated the temp gauge would hover just above 160. Since the problem I shut the engine down when the gauge hits 185. My fear is that it will keep going higher.

 

[Don S]

Re: It's Saturday - help me before I completely disassemble my engine

Are you sure you put the thermostat back in the right direction?

 

[harleyfool]

Re: It's Saturday - help me before I completely disassemble my engine

With the housing for the thermostat out of the boat and on my work bench upside down - the spring part of the thermostat is up and visible.

 

[Don S]

Re: It's Saturday - help me before I completely disassemble my engine

Is the temperature around the sending unit actually 180? to 185?. Can you check it with one of those IR temp guns? If it's cool there, then you have a problem with the sender, gauge, or wiring.

In picture below, which hose is warm when you are running, and is it HOT?

 

[harleyfool]

Re: It's Saturday - help me before I completely disassemble my engine

Hose D and the thermostat housing are warm. At a supposed reading of 185 degrees I can still place my hand on both and leave it on them. Now that you mention it I expected it to be uncomfortably hot.

I guess what has me perplexed is that everything was ok. At some point during the 2 1/2 -3 hour cruise the impeller gave up the ghost. The engine high temp alarm did not go off. It was probably a 1/2 hour interval between turning off engine, pulling boat, hauling to cottage, and attempting to flush with muffs. At that point the temp gauge was reading 180+ degrees. In the past, at cruise it did hover slightly above 160 degrees. Hard to believe sender/gauge/impeller all expired at the same time.

 

[meesh]

Re: It's Saturday - help me before I completely disassemble my engine

Do you have enough water pressure? Low hose pressure will run hot on muffs.

 

[harleyfool]

Re: It's Saturday - help me before I completely disassemble my engine

No, very good hose pressure.

If I can find/borrow an IR temp gun - how close should the measured temp of the hose "d" or the thermostat housing be to the internal water temperature??

 

[harleyfool]

Re: It's Saturday - help me before I completely disassemble my engine

What about a damaged circulating pump as a possibility??

I did take off the pulley. There was no obvious leak. The shaft spun easily. I could hear water movement.

When I force water down hose "d" into the circulating pump it did flow out thru the top of the engine where I had removed the thermostat housing. I do not think the water flow caused the circulation pump shaft to turn. Should the vanes on the pump spun or prevented water flow?? Could the vanes of this pump be damaged as a consequence of the impeller failure??

 

[Lou C]

Re: It's Saturday - help me before I completely disassemble my engine

It should run right at 160 F...at least my 4.3 with the same thermo housing design does...you are sure the stat opens at that temp....the warm to hot thermo housing and big hose and cool hoses to the manifolds is pretty much normal...how about any blockage in the riser passages? You said the impeller lost fins but did not find them in thermo housing so where are they?First verify temp...then look for more blockages...are you sure you replaced the impeller properly and the housing and associated parts do not have significant wear? That can impact on how much water it is able to pump...

 

[Apollo75]

Re: It's Saturday - help me before I completely disassemble my engine

Maybe you got everything out and it is a problem running on muffs.

It is uncomfortable for me to hold my hand on something at 140-degrees.

When I run on muffs at reduced volume like I am supposed to by Mercruiser --- my port side gets hotter if I am parked at the slanting curb (port side up). Also, the same hoses that runs to different assemblies from the thermostat housing run at different temperatures. When I put it in water and run it ---> both sides seems to even out temperature wise.

I hope yours is the same


OFM

_____________________________________
"If the boat is not sinking or on fire ---- Relax."

 

[harleyfool]

Re: It's Saturday - help me before I completely disassemble my engine

If I remove the thermostat and run the motor will that help the diagnosis?

If it over heats without a thermostat - what does that mean?

If is doesn't - does that mean the the thermostat is faulty? Or could there still be another issue?

 

[Apollo75]

Re: It's Saturday - help me before I completely disassemble my engine

Okay --- new water pump, cleaned out everything you can think of -- exhaust is cool and with good water flow.

Engine running a little warm ---- thermostat may just be sticking a little --- let it run till it gets up to 210 or so --- if it doesn't start to act like normal --- pull that thermostat gasket out of your back pocket and jurk that thermostat out of there

If it wasn't very far to the lake --- I would go to the lake and check it there with some beer and a fishing pole

Let me know if I got all the information right.

OFM

_____________________________________
"If the boat is not sinking or on fire ---- Relax."

 

[Apollo75]

Re: It's Saturday - help me before I completely disassemble my engine

I really don't think you can diagnose that cooling issue on muffs -- I would take it to the lake and run it ---- rpms with the impeller in the water will probably be fine.

I would rather work on my boat at the lake anyway if it was just a little temp issue, I do it all the time --- take my tools and tinker


OFM