thermostat

[Cool It]

hey guys-I have a question about my thermostat-I have a 2000 24 ft searay sundancer- 5.7 EFI bravo two Mercruiser- I always had a 160 thermostat and the boat ran fine at about 170 degrees now this season using a new mechanic and he put in a 140 thermostat im running at low speed temp is about 155-160 but as soon as I heat up good and run at about 3400 rpms I run at about 170 degrees now an alarm went off - oil pressure looks ok and outdrive oil is fine so Im thinking it must be the temp -first of all should my engine have a 160 0r 140 -or does it not matter and if it calls for a 160 can that alarm be because it has a 140 and its running closer to 170? also the running pressure on oil is 40 so I believe thats fine -sometimes when I come of a run the pressure drops to about ten at idle speed is that ok? sorry for the long winded question but just trying to explain it the best I can Thanks

 

[Don S]

Re: thermostat

If you have a raw water cooled engine, it should have a 160? thermostat in it, not a 140? The engines ECM is calabrated for the 160.
What did this alarm sound like steady beep, intermittent beeping, or something else?

 

[Cool It]

Re: thermostat

Hey don thanks -the alarm is steady

 

[Don S]

Re: thermostat

The alarm will only come on with overtemp, not too cold. Otherwise when you first start the engine you would have an alarm till it warmed up.
You may just have a bad temp or low oil SWITCH or the sensor in the gear lube is faulty. Disconnect the alarm switches one at a time to find which one it is.

 

[Cool It]

Re: thermostat

I put the 160 thermostat in temp is perfect-I think the alrm is coming from the low oil switch because it seems to go off if I come from a cruising spead down qiuckly to an idle -the oil pressure drops to about 8-10 psi aproxamatly and then the alarm hits -everything else looks ok. the alarm goes off pretty quick as soon as I get the pressure up . -where is the switch located -I might as well try that first? and what should a switch cost about-should I use merc part or is after market fine? Thanks

 

[Cool It]

Re: thermostat

actually my question now should be if the switch is bad will that cause the pressure to go down that low maybe 8-10psi usually the lowest I have normally seen is 20