Running temp for QSB 5.9 engines.

[marks737]

Hello,

My engines at cruise power (75-80% load) are running about 185 deg.  Wondering if this is a concern at all. Aftercoolers will be serviced this winter.  I have 2005 QSB 5.9 engines.  What should the normal operating temp range be?

Topic

[pwrobert]

Lost response

I posted a lengthy reply with a couple pictures but it seems to be lost in space. Any errors on my part?

[pwrobert]

Redundancy

Oil pressure, Engine temp, boost and fuel tank levels are all critical info to me especially since I often travle to the Bahama Out Islands where there is almost no help of any kind. I have Three oil pressure senders, three engine temp senders and two boost gauge setups and now a recently installed SMX EGT gauge as well.  Some are to digital gauges, some are to regular analog gauges and others are digital to NMEA 2000 for showing up on Chart Plotters.  They all vary slightly – maybe within 5 degrees or a couple of pounds but it is great assurance to know that there is more than one source to be able to instantly compare.  Also there is a Hart tank monitor as a final failsafe to fuel level checking – it is purely mechanical and non electric.  Can’t read it on the bridge but can be checked when filling up or at dock before leaving on long legs of a trip if any questions. Attachment photos show my digital guage and analogs right next to each other and are somewhat duplicated at the Lower Station. Second photo is the sender placements on the engine.  Different places can lead to a few degrees of discrepancy but not enough to worry about. Running at 2300-2400 RPM (normally cruise 2250- 2350 RPM) the engine temps with the SMX 160F thermostats stay between 155- 167F and the Oil  pressure depending on engine temp 30-60 PSI.  EGT 950F Port and 850F Starboard at cruise, I carry 300 gallons in three tanks and I like to know when to change tanks and try to never let any tank go below 20 gallons before shifting to another.  Boost 5 PSI Port and 7 PSI Starboard at those cruises.  17-18 Gal/Hr at usual loads.  18-20.5 MPH. So if any of those numbers start to not agree I get a heads up to start looking.  

[Tony Athens]

You did a very good job sorting it out….You are one of the 1st guys that also saw that engine loading ( or over loading) plays a part in the ovetall cooling of the engine..  ……………………Again—–GOOD JOB!

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Richard Scott

[marks737]

Thanks for the input!

[Richard Scott]

Wow!

JUST went all through this. Last owner spent a LOT of money of trying to figure out an 11 degree differential between the motors. I was running at in the Potomac at 194 on my Port motor, and 183 on my Stbd. Heat exchangers, oil coolers and after-coolers all professionally overhauled, the Seaboard way.  New raw water pumps, coolant, thermostats, hoses, belts, etc etc. Nothing worked. Turned out to be a combination of being overpropped, and the hose from the HE to the exhaust on the port side had a severally restricted hose. They had used an old universal radiator hose and it was pinched. Not something you would generally look for, and definately nothing anyone saw when troubleshooting this thing. I repitched down to 21×21 and replaced the hose. Runs at 183F (port) 179F (stbd) at 2650 (75% load), 25mph and 13gph (per motor). I WASat 2400 rpm, 75% load, 21 mph and 15gph (per motor). This is in the very warm Potomac. 185 is not high, but bears looking at.

1 user thanked author for this post.

Tony Athens

[Jeff Hall]

Doesn’t sound too far off from mine. Maybe 5-7 degrees higher. Here’s a picture from this morning cruising up the bay. About 40 minutes into our trip. <br /><br /><br /><br />

 

 

 

[Author]

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