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Update to higher temps

R

rmm

Regular Contributor
Following up on my posts about high temps on starboard 454 where gauge showing about 183-185 degrees at 300rpm cruise (never measured at T Stat). So went back down yesterday and did the following:

- corrected/replaced gasket in water pump
- fixed output hose on pump - hard to see and 2nd hose clamp was
tightened on hose not over fitting
- opened and cleaned heatxchanger
- replaced thermostat with 160 deg t stat (dont knwo what old was)

Anyway to tell what the old thermostat is? Only markings are on bottom and say 17 J7 and VI42?? Also noticed if look inside from top new one has 2 rivets and one hole open, where old one has 3 look like rivets no hole open.

Then ran boat for 45 mintues at varying sppeds as well as start and stop, usually cruise at 3100, water temp was 89 degrees. Results were:

3000-3200 rpm - 21-22.6kts, P=13gph/S=14gph

Port temp: Gauge 168-172 / T Stat housing - 172-178
Starboard Temp: Gauge 172-175 / T Stat 176-180

3400 rpm - 25.3 kts

Port temp: Gauge 172 / T Stat housing - 174-176
Starboard Temp: Gauge 175 / T Stat 177-180

On returning to dock a few other measurments:

At 1100 rpm after coming off plane and long run:

Port temp: Gauge 161 / T Stat housing - 171
Starboard Temp: Gauge 170 / T Stat 175

OIL pressures running at Gauge - P=33 / S = 35

Back at dock took a few other measurements:

Coolant tanks - P=154 / S=162
Manifolds - P=163-165 / S= 168-172 is this a little warm)
T Stat - P=168 / S = 162
Elbow/Riser - 125-135


On taking readings at the thermostat housing I did notice they were consistently 5 degrees higher than the guages. It seems the Starboard motor may still be a little warm at low speeds. Any thoughts here?

Generally think am happy with the readings and seems within range. Any input would be appreciated, thanks ALL for the assitance!
 
It looks better; it appears the starboard cooling system is a bit more stressed than the port side. Note on the stb thermo housing an 18 deg rise from idle to cruise, on the port side only a 6 to 8 deg rise. I think there is still not much margin on the stb side but right now, its just good enough. Is there steam out the exhaust on either side?
Next time out, take some engine oil temp readings at the u cooler. Should be around 200 degree input.

The one odd reading is the last set, where the engine shows warmer than exh manifold/port side. That might be measurement error. Those manifolds just add temp to the same water exiting the thermo housing.
 
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Will check the U cooler temps. On the temp difference on Port is actually more like 7-10 deg difference if look at temps across the T Stat housing vs the Gauge. On Star is only like 5-7 deg.

So what is the more accurate temp the gauge or gun on the tstat? Also what is too hot on these motors? Was talking to guy at dock with same setup and he says always runs 185-190 at cruise and his motors are only a few years old.
 
My guess is that the gun will have a greater accuracy. BUT, I will like to see some other thoughts. I know my own boat has analog gauges and a needle width is probably 5 degrees in addition to the impedance of the sender
 
rmm said:
Will check the U cooler temps. On the temp difference on Port is actually more like 7-10 deg difference if look at temps across the T Stat housing vs the Gauge. On Star is only like 5-7 deg.

So what is the more accurate temp the gauge or gun on the tstat? Also what is too hot on these motors? Was talking to guy at dock with same setup and he says always runs 185-190 at cruise and his motors are only a few years old.
Click to expand...

I threw out all the gauge measurements, i'm banking on the ir gun.
New engines reportedly have higher temp thermostats. But, proceed with caution on thinking of using 180 deg stats. The heat load of the exh. manifolds may easily push you to boiling, depending on coolant and cap pressure rating. There are other differences in more modern engines, less valve train loss, ECU temp monitoring, better mixture control, and likely more.
 
A big change on the newer stuff is coolant system pressure caps are 16 psi vs 7 on the old ones.

A good ir gun with be an order of magnitude more accurate than the normal gauge.

Another potential drawback to the higher operating temps is an increase in what may get precipitated on the raw side. The exhaust elbows are most likely to suffer there.

the last set of numbers on the old T-stat infer a 142 degree opening - raw water cooled standard parts.
 
The latest numbers look quite a bit better and you may well be able to run with those for a while. Cooling is a tick marginal on the starboard side so keep an eye on the temp. gauge during high cruise. If it climbs over 185F I'd back it down and investigate further.

The IR gun is inherently more accurate but bear in mind it must be used in an even and consistent manner when making comparisions. The focal length of the IR detector is an important consideration here so shoot your temps at the recommended distance for your gun and at the same angle and at the same physical place on both engines.

As mentioned in another post, I have an 18 degree rise on my port motor from idle to cruise from 160F to 178F. New impeller and risers/elbows on starboard side; no apparent obstruction in raw water intake or oil cooler and heat exchanger cleaned last year.

I'm going to swap raw water pumps from P to S and see what happens. Its free and easy.

Next I'll consider replacing the oil cooler on the starboard side. What the heck, its pretty old anyway. I may consider swaping these P to S as well. However I do try to minimize oily messes and I might just replace a time bomb anyway.

Then possibly have the starboard heat exchanger cleaned again.

I could live with a 10 degree rise but 18 degrees in a 65 degree ocean is too much.
 
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