Thermostats

[johnjen50]

Ok so when I visited my Detroit place to pick up a couple of thermostats for my 871 ti's I gave him the engine serial numbers and he tells me the engines take 160 deree t-stats. Manual says these engines should take either a 170 or 180 t-stat. Why would the serial number be bringing up a 160???? Unfortunately I followed his lead and bought the 160's but I'm thinking of exchanging for the 170's. What says the brain trust ?

[jim rosenthal]

This gets brought up fairly often. The concensus seems to be that 160 is too low.

[johnjen50]

Right thanks Jim. I just can't for the life of me figure out why the Detroitarts guy brings up my serial numbers and it refers him to a 160. Even the manual says these engines should use the 170 or 180. Weird. Being in the northeast the water is a tad cooler as well, making me want to lean toward a 170 anyway.

[MikeP]

When I bought it, my 53MY had: one engine with a 180 and a 170, the other with a 160 and a 180!

As Forrest said, "...you never know what you're gonna get."

I did the serial number check and, as yours, they said it came with 160's. I bought/installed new 160's but for our normal cruising the motors never got above 165 which, IMO, is too cool for optimum operation. So I bought some 170's several years ago.

One of these days I'll install them.

[bobk]

On my 692's I pulled the 160's and replaced with 170's. At WOT they reach about 175.

Bobk

[Glory]

When I bought it, my 53MY had: one engine with a 180 and a 170, the other with a 160 and a 180!

As Forrest said, "...you never know what you're gonna get."

I did the serial number check and, as yours, they said it came with 160's. I bought/installed new 160's but for our normal cruising the motors never got above 165 which, IMO, is too cool for optimum operation. So I bought some 170's several years ago.

One of these days I'll install them.

Mike, I have a few projects like that😞.

JM

[saltshaker]

This has come up several times and in many different threads. Seems the general consensus is that the 160s will make the engine run too cool and the 170s seem to make a huge difference in keeping the operating temps in an ideal range. This assumes ther rest of the colling system is in proper working order. I had 160s and switched to 170s in my 6V92TAs. Temps were ideal with the 170s.

[jim rosenthal]

I think if the cooling system is operating as it should, the thermostat should be the controlling factor in engine temp, right? IE the cooling system should have capacity beyond that figure. I don't have DDs, but I would not want my engines running at 160- I think it's too low as well. I would think the engines would carbon up at that temp.

[johnjen50]

Agreed all. I swapped the 160's for 170's today. Installed one and pretty much done with the other. Dropped one of the spacers securing the shut down solenoid into the bilge and spent 35 minutes looking for it before giving up and resolving to get one tomorrow. I was speaking to someone with a 53 MY and he said at WOT he never got above 165. I figured I have no intention of running at WOT all the time so better run a warmer tstat.

[MikeP]

IN THEORY, the thermostat is there to ensure that the engine stays at the same temp whether operating at hull speed or WOT. Of course, in practice, some cooling systems are more equal than others in being able to accomplish this. The DD marine cooling systems seem to be marginal as far as cooling capacity at WOT if they are in any less than perfect condition. OTOH, at idle they will never get up to a decent temp regardless of the Tstat temp rating and DD states in the service manual that 800 RPM is the minimum speed for long term "idling" in order to keep temps up to an acceptable level.

When our 8V71Ti's HE's are newly cleaned, the engine coolant temps at WOT will stay at around 180-185 in an hour of running at WOT. That leads me to believe they will continue to do that for as long as the fuel holds out. If they have not been cleaned for a year, the temps will rise above that after a few minutes at WOT.