port engine running hot - updated numbers

I got my port side shaft aligned and was able to get out at cruise speed. If you can recall my last post where the whole cooling system is new on both engines, here are the actual numbers. I ran all last year like this and it never overheated but just isn't right. All of the work was done last off season, nothing recent other than new seacocks and raw water scoops. Same results as last year though.

The port side gauge shoots up really fast. Within a few minutes of idling it's reading 160 where the Stb side is maybe 120. After running for about 1/2 hour and 10-15 mins at 3,000+, here are the numbers:

Gauge reading 168 - thermostat housing is 157 (measured at the base this time instead of the bleed screw which is more accurate)
Exh manifolds are both 175
Risers/elbows are both in the low 100's
Both u-coolers hoses are (IN/OUT) are in the 70's (close to water temp)
Hose into the H/E is 150-160 where the Stb side is around 130
Hose into the manifold is 135 and 170 coming OUT (hatch was on so only able to shoot one side).

There's about a 25-40 degree difference between the exhaust manifolds on each engine. The riser/elbow temps are somehow in the same range on each side though.

The other thing I noticed is a lot of air bubbles and swirling of the water in the strainer site glass. The other side was full of water but you couldn't really "see" it like the port/hot side. It's a straight connection from the raw water intake and into the strainer. Hoses are new and clamps are tight.

The raw water flow out of the exhaust seems to be about the same. Hard to tell at speed on my boat because the exhaust is partially underwater.

At WOT, the port engine gets to about 190, Starboard is a little over 170.

Engines are FWC, 454's, 1988. I can post the Stb side numbers but they seem to be ok all around.

Any ideas?

Bob

Those bubbles are an air leak. You need to correct that.

Jeff

Yes, the air in the RW side is notable, and should be attacked. You did report something confusing to me: "Hose into the manifold is 135 and 170 coming OUT" and, "thermostat housing is 157". There is a hose directly connecting the thermo housing to the exh manifold, and these should be the same temperature, correct? Are you shooting metal in both cases? Or maybe the hose on one and the metal on the other? See if there is a difference in measurement between a hose end and the attached metal device.
Something doesn't look right there.
Overall though, this engine is not overheating. If the 130 is real on the on the other engine, its' running too cold.

I thought the bubbles were a red flag, let me check that out today. I'm assuming the air can only be from one of two places - each end of the hose or a fitting/seal on the strainer itself, not upstream from the strainer. Can an air leak work its way back in the system?

Yes, the thermostat housing connects to each side of the exhaust manfolds. I tried to take the temp readings on the bronze elbow hose connections. Maybe that's not the best place but the "cool" engine readings were basically the same in/out (manifold) where the "hot" engine shows*about a 30-35 degree difference.

You raise an interesting point. Is the "hot" engine actually to spec and the other engine the issue?

Are my 135-150 readings on the exhaust manifolds too cold where the other side is 175-180? My gauges seem to be fairly close and when it's all said and done, I get about a 20 degree difference on each engine. WOT 190 degrees vs about 170.

Thermostats on both engines are new and the same. Maybe I have a bad/slow stat on the Stb side?

Bob

"Are my 135-150 readings on the exhaust manifolds too cold where the other side is 175-180?"

Yes, the exhaust manifold, at cruise, should not see less than 165 deg, at the input, the output some 30 degrees higher. Your stb engine thermostat is either the wrong temp, installed wrong, or stuck open, it would seem.

Is this your config?:

Dave,

Yes, that's my setup. I'm pretty convinced I have two different problems now...

1) Stb engine is actually too cold. I'll pick up another thermostat and swap it out. I doubt I installed it upside down but you never know. I assume I can get one at NAPA easily enough - 160 degree correct?

2) Port engine temps are closer to what they should be but the quick rise I see at WOT is probably a little higher than normal because the air leak downstream of the strainer.

thanks,
Bob

Yes, Bob. I think you are one the right track. Note that the exhaust manifolds will rapidly heat with a cold engine, since there is no water flow thru the manifolds during warm up. When the engine thermostat opens, flow then starts thru the manifolds and into the HE. I'm not sure what to say about the quick engine temp rise; it's actually a good thing the engine warms up fast, and if the engine doesn't run hot at high power settings, I wouldn't worry a lot about that. The air in the strainer is not normal, however, and I can't see how the air can "run backwards" thru the system. Maybe just a strainer gasket there is the cause. 160 deg on the stat is correct.

Dave,

I made an interesting discovery. Went down with the new thermo in hand and removed the thermo housing to get the old one (new last year) removed.

It was cocked to one side and 3 the legged "cage" on top was broken in two places. It looks like someone hammered it in place. Unfortunately, the "someone" would have been me. I have no idea how I managed this.....it must have shifted and then gotten partially crushed when I torqued down the housing. I've changed a half a dozen thermos in cars over the years, it's not really that hard

Anyway, I replaced it with a new and fired it up. Temp came up real quick, just like the other engine. The gauge read about 175 in the slip, housing was a hair over 160. A little higher than the other side but I need to run it, top it off and take new readings.

I also checked/tightened everything on the strainer back to the seacock on the port engine. I ran some non petroleum grease around the seals and will check that for bubbles next run too.

Thanks for your help, I'm glad you picked up on the cold engine temps being the real issue.

Bob