engine overheating

B

blue_nova

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Joined
Apr 27, 2006
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21040
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De winterizing carver 360 with volvo penta 8.1gi
internal cooled engines.
one engine overheats on warm up.
a.replaced raw water impeller, old one looked good. still overheated.
b.removed thermostat, ran without, still overheated.

What do I check next?
Thanks.
Blue no va
 
Removing the thermostat is never a good test and can contribute to overheating. Perhaps you have a hose collapsing on the raw water cooling side? There are other causes as well, you didn't mention if the fresh water (closed cooling) side pump was looked at? You didn't state the year of the engine are your risers in good shape or have they been checked?
Bill
 
More info would help. here are a few quick questions to consider....

How long has the boat been in the water and is it an area of high fouling rate and how long has the over heat issue been evident and to what temps?
If warmed up at the dock , does it overheat at both idle and higher RPM, or just low rpm or just higher RPM?
Coolant overflow or other loss of coolant? Does it smell hot? Steam evident in the exhaust?
As HK suggests the RW engine intake scoop strainer may have growth or if recently painted , paint may be seriously obstructing flow. Have you checked the RW basket strainer?
Is the seacock fully opened?
Is the belt tight enough to not slip on the RW pump? (That would not affect the RW pump if it is a crank-mount & probably is.)
Have hoses been removed from the pump recently and possibly reinstalled on the opposite inlet/outlet?
Have you checked/tightened all hose clamps and RW basket strainer cap o-ring seal to keep suction air out?
Have you ever back-flushed the RW coolers for crankcase oil, transmissions and fuel pumps?
Once fully warmed can you keep your palm on the top of the riser/elbows indefinitely at low and sustained cruise rpm 's? If yes without pain , look to the FW side of the system . If no, -RW side. Age of Riser/elbows?
Can you see the exhaust outlets to check for visibly good RW flow there? (A general spec for gas engines RW pump min. flow is 5 gallons in 15 seconds at 4000 rpm.)
Has coolant been changed recently , and trapped air possibly not fully purged yet?
 
Glad to see Charlie and Sandy here, Blue Nova these guys know what they are talking about and can help you if you answer their questions.
Bill
 
quote:
Originally posted by jtybt15

Yeah, what's the time frame 'til it overheats?

Click to expand...

He said it overheats on warm up. I guess that means while still tied to the dock Charlie...
Bill
 
Under 10 min? Under 20 min?

FWC has the cooling tubes within a bath of raw water. IF... the engine circulating pump is working but the raw water pump aint, the coolant in the engine will still circulate thru the heat exchanger.

NOW, if the raw water pump works but the engine circulating pump doesn't work, the stagnant coolant in the engine will over heat in, maybe 10-12 min or maybe 5 min after the thermostat gets hot enuff to open at idle.

Without being there, it's a process of elimination, but we need the info to eliminate.
 
quote:
Originally posted by Billylll

quote:
Originally posted by jtybt15

Yeah, what's the time frame 'til it overheats?

Click to expand...

He said it overheats on warm up. I guess that means while still tied to the dock Charlie...
Bill

Click to expand...


Perhaps but not necessarily , Bill. A lot of boaters leave the dock long before the engines reach normal operating temps. I do it often myself as it's a 1/2 NM idle out to the haba jetties. Some others seem to just light up cold and hit the throttle in a minute and it "warms up" on plane.
 
I have never just started the motors and left the dock immediately. I have a routine by the time we untie and unhook the water and electric and dock lines it's at least 15 minutes and the engines are running about 5 degrees below operating. We just putt along for the first 10 minutes through no wake zones to deeper water before I try and get the boat on plane. We have lots of skinny water and my boat needs at least 5 feet of water under her hull or it will never get on plane. She's heavy....
Bill
 
Thanks for all the info:
This is during dewinterizing process:
Model is 8.1Gil-C Year 2003
Engine is overheating in 10 minutes at dock during warm up
I replaced the impeller, old one looked fine.
I removed the thermostat and overheated without.
Tested thermostat and checked out fine, put it back in, and still over temp.
I removed strainer and still got over temp.
Water flows well with strainer top off and sea cock opened.
Coolant reserve tank is full.

Thanks in advance for your help
 
Is the alarm sounding? What temps on the gauge?
Do you have good flow at the inlet hose to the RW pump after it has gone through any upstream coolers? Note, 1/2 normal flow at any given rpm or just cracking the strainer lid still looks like a LOT.
If you let the pump outlet hose run into a bucket (before it has reached over-temp, is there a lot of air in the stream?
Did you look closely at the housing wear surfaces of the RW pump? If scored there, even with a new impeller you may not have suction to draw water at low rpm when the impeller vanes must contact that surface. At higher RPM underway, that is not an issue because it just becomes a centrifugal pump mostly pushing water and vanes are not touching the wear surface.
When it has elevated temps , again, what is your palm telling you about the riser/elbow tops , and does that change if you increase RPMs?
Is the circ pump pulley turning properly and no sign of leak at the circ pump weep hole?
 
When you first start up, pull the 'radiator' cap and watch to see if the coolant is swirling. Moving coolant means the engine circulating pump is working...though it sounds like it's bad.
 
>Is the alarm sounding? What temps on the gauge?
Yes, Alarm sounds at 205 on gauge.

Do you have good flow at the inlet hose to the RW pump after it has gone through any upstream coolers? Note, 1/2 normal flow at any given rpm or just cracking the strainer lid still looks like a LOT.
>If you let the pump outlet hose run into a bucket (before it has reached over-temp, is there a lot of air in the stream?
will try this and let you know

>Did you look closely at the housing wear surfaces of the RW pump? If scored there, even with a new impeller you may not have suction to draw >water at low rpm when the impeller vanes must contact that surface.
Examined housing very closely, looked good, impeller looked good.

>When it has elevated temps , again, what is your palm telling you about the riser/elbow tops , and does that change if you increase RPMs?
Riser temps for good engine 0 mins:68, 5 mins:69, 10 mins 89, 15 mins:106
Riser temps for bad engine 0 mins:62, 5 mins:122, 10 mins:303, 15 mins 350
Did not try to increase rpms, but will try and let you know

Is the circ pump pulley turning properly and no sign of leak at the circ pump weep hole?
Yes, belt is tight and pump turning. No leaks.
Thanks,again
 
Clogged Heat Exchanger? Is this a "Half FWC" system (coolant in Engine but Not Exhaust Manifolds)? Or a "Full FWC" system (coolant in Manifolds also, requires a larger Heat Exchanger than Half System)?
Clogged raw cooling water discharge at Riser? Can you see your discharge water at the exhaust pipes?
I'm wondering if some rust developed over the storage time, broke loose now, plugged the water discharge passages.
 
OK, so I spent the afternoon in the engine room:
1. using flush port, I ran a hose to the house and was able to test for air leaks by shutting the sea cock and adding a clear hose at the output of the raw water pump.

Found no water leaks with hose shut off. However, with output hose open, water flowed through the raw water pump.

Question: shouldn't the pump when not turning, block flow of water?

2. I attached hose from house to output hose from raw water pump to cool the engine. And had clear hose from pump into bucket. Ran engine and no water came out of raw water pump. Also, engine temperature was fine on hose.

3. To double check the flow of raw water to the pump, I connected a wet/dry vac to the pump input hose and it filled the tank in the same time as when I stuck the hose directly in the lake. So water flowing freely to pump.

So, question now is aside from pump housing, what could issue be?

Thanks so much
 
Is the impeller actually turning when the engine is running? Perhaps the shaft is broken.
 
or the impeller isn't turning. Did you install the key/keyway.

Not sure how water is getting by the impeller. Gotta inspect the body.
 
quote:
Originally posted by jtybt15

or the impeller isn't turning. Did you install the key/keyway.

Not sure how water is getting by the impeller. Gotta inspect the body.

Click to expand...

Charlie I'm thinking he is using a pressurized water supply so it would force it's way through a non operating RW pump.
Bill
 
quote:

Charlie I'm thinking he is using a pressurized water supply so it would force it's way through a non operating RW pump.
Bill

Click to expand...


It could especially if the if the impeller housing and cover plate are worn.
 
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