Another Overheating Issue @ Idle

[cyauch]

When I did these tests, I had installed a new Original Volvo Penta raw water pump. These might give you a clue. Tests done before finding the cause was the Bronze tube.

wow. yea, i have nothing like that kinda flow at any RPM no matter if the t-stat is open or closed. There seems to be more 'flow' until the stat opens, but it sure isn't that kinda flow like in your video. I dread pulling the lower unit. my fear is snapping the head of bolt or it being a complete PITA to get off

 

[alldodge]

Agree with Bruce
You want the clear hose on the input hose from the pump.
Can you hold your hand on the thermostat housing?

 

[cyauch]

Yes, i can hold my hand on the t-stat housing and risers. they are warm and if i hold it it there long enough, it gets uncomfortable, but not scalding.

I still have a section of clear hose left over. i can add another one on the hose indicated and see how that goes, but may be a day or two before i can get it to a ramp to test.

My theory on the blue flush port is that my well pump was providing enough water pressure to the system to make up for deficiencies when operated while in the water. it stayed cool for an entire hour running in my driveway. is that a safe assumption?

 

[alldodge]

Yes, i can hold my hand on the t-stat housing and risers. they are warm and if i hold it it there long enough, it gets uncomfortable, but not scalding.

Being able to do that tells me its not overheating. The gauge is reading over 180* and your able to keep your hand on the thermostat, its the gauge or sensor

 

[cyauch]

interesting. so now im second guessing myself. i know i touched the risers several times when it was reading 175 on the gauge and hit the tstat housing once or twice. i need to put back in water and run though those steps again. was checking so many things yesterday. i know i never scalded my hand but again, seconding guessing if i touched it after the engine shut down. pretty sure i did but....

so the sending unit is interesting. is it normal for the engine to shut down on its own if a certain temp is reached? when it does shut down, im now not getting the alarm anymore (was prior to tstat replace and oil cooler backflush). logic tells me yes cuz of computer but have to ask.

and i think i can assume it would be a sending unit instead of gauge since the engine shuts down consistently once north of 175 is reached? i do remembet pulling the connector while it was running. started beeping after 30 seconds. let it beep 20 times ir so then plugged connector back. beep a few more times then stopped. think that only proves a good electrical ckt though but not a good or bad sending unit

so i have three days of rain coming. my plan of attack is
- pull the RWP
- pull the circ pump ( gaskets should be here tomorrow)
- pull lower unit and check the tube mentioned prior
- replace the tstat probe (is there an electrical check that can or should be performed ?)

 

[alldodge]

Your motor has two senders, one goes to the gauge which gives you a visual of temp and provides no info to the ECM. The ECM sensor tells it if its overheating, and it will shut the motor down and throw codes.

 

[cyauch]

thanks AD. was able to drop her in this afternoon because i really wanted to confirm if i could touch the risers or tstat housing or not without pain. the answer is yes...and no.
so again sitting on trailer in water, backend floating. idled for 30 mins. tstat opened. housing read 143 - 155. top of risers read 125 -140 with oil filter side being the 140. manifolds read in the same range.
so went and ran it. obviously housing, risers, and manifolds increased as did gauge, but at idle and out of gear, temps slowly came back down to ranges above
then went and ran it hard close to WOT and played with trim up and down. then back to idle and out of gear. thats when the risers and tstat housing were too hot to hold. stat housing was reading 180 - 190. gauge stopped a tick above 175. didnt wait for engine to shutdown since in middle of river. went back to launch and let it idle there. engine shut off. gauge had to be ~180 - 190. manifold and stat housing readings were close to that reading
still not seeing any water to manifolds obce stat opens. still saw no air bubbles in RWP suction side.
but did notice again after stat is open that if i hit the throttle quickly i can see what appears to be a drop in water flow in the suction side and appears in the discharge side. it quickly goes away.

but as i stated before i plan on pulling the RWP, circ pump, and the lower gear housing anyway so ill inspect that. im hoping i dont have an air leak. dreading having to pull the engine again so trying to look at everything else thats 'eaiser'. ut it almost behaving like not enough water is being pushed / pulled with enough volume to cool things down. maybe the impeller / RWP inspection will reveal i screwed that up on install

 

[Horigan]

@cyauch, Have you done a complete backflush of the raw water cooling system? It seems like you have a flow restriction that prevents sufficient flow at high power. Seems to be a common theme with all three overheat at idle threads.

 

[cyauch]

@cyauch, Have you done a complete backflush of the raw water cooling system? It seems like you have a flow restriction that prevents sufficient flow at high power. Seems to be a common theme with all three overheat at idle threads.

kinda sorta i think? im still learning about I/O's so...

what i did was insert 1" pvc pipe into suction hose disconnected at the RWP. see post #12 of this thread. i have pic there. then turned hose on and let that run a few minutes. occasionally i would cycle the valve to give a little umpph to the outflow. my next step, weather permitting, is to disconnect from oil cooler and let it drain in bilge. plus, i want to inspect the cooler itself to see if its narrowed up

so the rain has started and will be like like this for a few days. so tonight i took off the RWP and i honestly think this thing is toast. i see discoloration, like rust, on the bearing surface thats attached to the pulley. i also see grooves and my fingernail definitely grabs when i drag it. and inside the housing, while the part the impeller fins contact kinda looks good, theres a noticeable groove in the center that i can feel. plus when looking straight into it, pretty sure im not supposed to see a dark circle. and theres a definite groove worn into that. maybe at least 1/16".

been looking at pics of new ones online and they look all shiny and smooth inside. logic tells me this is toast but since im a noob with this, other opinions appreciated.

as for the lower unit pipe inspection, thats on my list and will probably pull that tomorrow since the rain is here for a while

 

[cyauch]

one more pic. just noticed the impeller has been scrubbing the housing.

 

[alldodge]

The grooves are not good, but the impeller is fine

 

[cyauch]

The grooves are not good, but the impeller is fine

Thanks. Putting order together tonight for this and some gaskets that I'll need for other things i'll be checking the next couple of days.

Upon close inspection of the pump assembly, i noticed the wear patter in the outer housing is kinda 'sloped' if that makes sense? Think of an auto tire that leans in or out a tick at the top. It's definitely noticeable.

So while i plan on still taking some other things apart for inspection i have some tech questions about the groves (based on the condition, i'm gonna assume this is the original pump assy).

As i understand info post on threads here, grooves would / could allow water to 'slip' past the blades of the impeller. If this is correct, then yea, i think i can safely assume this is part of my problem, if not all of it. Still, I plan on continuing looking at other things.

But back to the grooves. If water is slipping past the impeller blades, wouldn't it not cavitate a little and generate some air bubbles? Just curious as i didn't see any obvious ones, but it was a PITA to stick head down there and watch so....

Next on the list is the lower unit and a look inside the oil / ps cooler....

Thanks again to everyone who's provided their thoughts and info to date. MUCH appreciated!!

 

[alldodge]

IMO, If bubbles are generated there may be so few not to notice

 

[cyauch]

Doing some research on a sea water pump i just noticed something odd. The pic i attached of the impeller shows a PN of 21213650. Yet, i can't find that part anywhere. Everything comes up as 21213660. I got this impeller last fall from a dealer in Alabama and provided the engine serial number.

Was 650 superseded by 660? if not, what does 650 go to? Doesn't come up on Cecil Marine's site either.

 

[alldodge]

Hey @bruceb58 can you assist with the impeller part number?

 

[bruceb58]

Hey @bruceb58 can you assist with the impeller part number?

I can help when I get home Thursday evening.

 

[bruceb58]

I was able to find this part number on volvo penta store

https://www.amazon.com/dp/B00K8EP10C/ref=cm_sw_r_cp_apa_fabc_4FD2DAJYY8RWF70RN9NM

 

[alldodge]

Thanks Bruce, and wow, $74 for an impeller

 

[bruceb58]

Thanks Bruce, and wow, $74 for an impeller

That's list price. I posted it on amazon for less. My mercruiser impeller was more than that.

 

[alldodge]

My mercruiser impeller was more than that.

The Merc Gen 7 impeller is about $30 to $42 depending where you find it, why the high cost?