Cummins running temps

[Russ Calasant]

I seem to remember this issue occurring when the local water temperature rises but I'm not sure. My motors usually run at 160 from warm up to shut down. Recently my port motor jumped up to 170 and starboard 179 after running up the rpms. At idle and steerage speeds they both return to 160. Anyone have any ideas? Impellers were changed last season as well as the port raw water pump.

 

[PMC]

I don't have anything to add, but will follow...Interested ;-)

 

[trit21]

I have not seen any rise in running temps since I have owned the boat due to increase in water temp. I have 6bta's and mine run 185-190 all the time, (that is where the B is designed and supposed to run BTW) may bump up a touch if I run at WOT for an extended time, like a degree or two. My first thought would be strainer, impeller and I will assume they are clear new as stated. Next would be blockage in aftercooler not allowing enough water to flow or maybe growth/blockage in your heat exchanger. Next thought would be the insides of the pump are worn and not allowing proper flow. It does happen where the cam, back plate, and housing wears and the correct amount of water flow can no longer be achieved. Replacement parts and or pump are required at that time. I replace my sherwood (know for nothing but problems) with SeaMAx pumps and I think they are worth a look.

 

[shinsr]

I run cummins QSC 500's. My runnning temps are, based on smartcraft, 169-172, have not jumped above. I change my impellers every other year as PM and have had no change in temp, they do drop down to around 160 at idle

 

[SR400DB]

I just replaced my OEM Sherwood pumps this year with Seamax. My temps are always in the 160-168 range. Aftercooler maintenance very other year and impellers annually. Water temps will range from 50 +/- to over 70 and I do not recall noticing any engine temp rise. Check the aftercoolers

 

[Sum Escape]

I have the QSC 500's. At cruise (2300-2400 RPMs) they always run about 170-175 dropping back to 160 at idle. At 2000-2200 they run in the high 160s. Been that way since new. New impellers every 2 years, no changes to operating temps.

 

[Sum Escape]

Found this on the CMD site. 160-178 appears to be the standard range.

Standard Thermostat Operating Range Start to Open.°C [°F] 71 [160]​

Full Open .......................................................... °C [°F] 81 [178]

 

[Rocket]

I had a similar issue on one motor only. THey found the fuel cooler had internally expanded and impeded water flow. Of course as all others mentioned, start with impellars and aftercooler maintenance.

 

[Jaws]

Russ,
I have not had this issue. My temps are always in the low 160's but I changed out to SeaMax pumps three years ago. Aftercooler? Fuel cooler? Check the vanes on the pumps; it's an easy look.
Make sure you are looking at the on-engine gauges, not the ones on the dash.

 

[dcharna]

I agree with everyone and wanted to add one note. Just because you changed your impeller doesn't mean that you didn't pick something up that took off a blade or two. I have had friends change their impeller and the next day ruin by picking up a rock or piece of wood. I would check that first.

Dan

 

[markrinker]

I seem to remember this issue occurring when the local water temperature rises but I'm not sure. My motors usually run at 160 from warm up to shut down. Recently my port motor jumped up to 170 and starboard 179 after running up the rpms. At idle and steerage speeds they both return to 160. Anyone have any ideas? Impellers were changed last season as well as the port raw water pump.

I think water temps are most likely your answer. Were thermostats changed out last season as well? We recently moved from Lake Superior where spring water temps ranged from 39f at launch to 48f at haulout 6/24 and never saw cruising temps over 160f. Moved the boat into Lake Union in Seattle and saw 180f when on plane in Lake Washington...first reaction same, then noted water temp of 68f (?) if memory serves me. I did see some variation port to starboard, which leads me to wonder if I have one thermostat sticking before fully open. My engines are CAT 3126s, but the idea is the same here...

 

[Russ Calasant]

Thanks all for your thoughts and insight. I did have a few barnacles in the strainers and I checked the impeller on the port side, all good. I ordered a seamax pump for the starboard side and will change that out, it needed to be done anyway. I suppose I will proceed from there.