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port engine running hotter

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bobct

Advanced Contributor
I went out for my shakedown cruise today and the port engine didn't fix itself over the winter :)

It runs hotter than the starboard engine which it did all of last year. It won't overheat but I would like to resolve it once and for all. Here are the temps I took today (IR gun) off both engines, curious what you guys think:

Starboard/Port

Gauge140/160
Top thermo housing 120/129
Left exh manifold 131/178
Right exh manifold 135/181
Left Riser - 120/108
Right Riser - 110/99

The following are new with no change - both gauges and matched sending units, coolant, thermostats, "U" coolers, H/E rodded out last year, Impellors, Stb Sherwood pump is brand new, Port has been swapped with another used pump, no change. All the strainer gaskets have been replaced, both seacocks and intake scoops are brand new this year.

The port engine heats up a lot faster the Stb and gets to 160 before port hits 120/125. I need an alignment so taking it slow, all readings taken after running around 2,000 RPM's for an hour. At cruise (last year) the difference in temp would narrow with port at 190 wide open with stb at 180.

What jumps out at me is the big difference in Exh manifold temps but somehow the "cool" engine temps are actually a little higher at the riser.

Both engine coolant pumps are original at around 1,000 hours. Everything I've read puts these at the bottom of the list, even my surveyor said they almost never go bad.

Any ideas?
 
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I think that more info is needed.
Are these open systems.... or closed cooling systems?

Also, please define "engine coolant pumps"!
I will assume that you are talking about the engine "circulating" pumps (not the sea water pumps).

If Circ Pumps, we can go back to the question of Open or Closed Cooling.

If closed cooling, the automotive version of the Circ Pump works just fine... but must be the short body.
These are inexpensive, and easy to change out.

If open (aka raw water cooled) you'll want the Marine version in order to have the bronze or SS impeller, special ceramic shaft seal, and SS rear cover.
The Marine version is more expensive, just as easy to change out.
I find it hard to believe that anyone would put these at the bottom of the list given the possibility that someone may have installed an automotive circ pump at one time.

Keep in mind that the cooling water leaves the engine on an "as needed" basis as the thermostat dictates.
Most sea water is being expelled out the exhaust (as long as the sea water pumps are working correctly, and it has a clear path).
Only a small portion is required for actual engine cooling demands.

Use the ole P of E... process of elimination... one item, and one item only until you find the problem. :)
 
I was stunned by the riser temps! This HAS to be a FWCooled motor with glycol cooliung the manifolds, right?

Jeff
 
sorry guys, all that info and I forgot the most basic question - yes, FWC '88 454's. Yes, I was referring to engine circulating pumps equivalent to a water pump on a car, those are original. Those came to mind because the manifold temps are so much higher. BTW, I changed those too along with riser/elbows about 100 hours ago.

Also forgot that all hoses were changed as well including exhaust....

Bob
 
Well, if the numbers are measured correctly, both engines are running too cold. They should be mid 160's at the thermostat housing at 3200 rpm cruise. If you measured all this at idle, then retake at cruise, after 15 minutes or so. The rise at the manifolds looks suspicious. 11 degrees on one engine and a whopping 50 degrees on the other. To be clear, the thermo housing at 129 degrees feeds a hose going to the 180 degree manifold, correct? At cruise speed the manifold should not rise its coolant 50 degrees. 20 is about normal. Is there steam at cruise? Also, measure the HE intake and output coolant temperature.
 
The temps were taken after about 30-45 mins at low cruise speed - 10 knots/2,000 RPM's. I tried to hit the bleed screw on top of the thermo housing as it had less paint than the housing iteself. Are you saying that the manifold temps should be the same or LOWER than the riser/elbow readings? I thought they should be higher as in my Stb engine but not by 50 degrees. Maybe I have an issue (different) with each engine?

I just looked at a video I took late last year. At 3,000 cruise port temp (all gauge readings) was 170, port 160. WOT for a couple of mins was port 190, Stb 180.

Yes, thermo hose goes to manifold on each engine.

Bob
 
Risers/elbows you can typically keep your hand on them for a time at cruise speed. The manifolds, no way. About a 185 to 190 exit temp. on those. So, the exit from the thermostat/engine is ~168, the exit from the manifolds is 20 deg higher, which is also the HE coolant INLET temp.
 
You stated that the hot running engine (port) has a used raw water pump, correct? Why not put the new (stb) raw water pump on the 'hot' engine? Also, have you hooked up clear sections of hose on the port engine to look for air leaks? Bob
 
I know I had the bleed screw(s) removed from the thermo housing when I refilled the system, and I believe I ran the engines until coolant came out.

One of the guys on the Trojan forum (same boat as mine) had this exact issue a couple of weeks ago. He just changed riser/elbows and didn't bleed the system afterwards but it worked itself out - problem solved

Because I did this work early last year, I ruled this out as a potential issue for me...... maybe not? I ran it about 100 hours last year.
 
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Sounds like you did most of it. It's been our experience that you need a few complete thermal cycles to fully purge all the air in the closed system. Assuming it is still full, I'd suspect you are aire free.

Any gaskets changed before/since the issue has been noted? The closed systems have two different gaskets and the wrong part will NOT let the system cool as designed.

measuring the temp at the HX outlet (closed side) may also be useful to have. the high manifold temp rise shows most of the heat is being absorbed there. This is consistent with the risers having lower temps (than the other engine) as the raw water isn't taking the heat out. The question is WHY is the heat transfer occuring?

If your exhaust outlets are above the waterline, you may want to do a visual between port and stbd to see if the raw water flow is comparable...best to measure it but a visual is usually worth the couple seconds.
 
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