225 mercury saltwater temperature rising after shut off

_vn_

Petty Officer 2nd Class
Joined
Apr 23, 2012
Messages
131
Hi, I just started having this weird problem where one of the engines would start overheating after it was shut off. I was out fishing and constantly moving boat to get a drift so after couple of hours one of the engines beeped an overheat alarm. I tested few times and it would happen every time, temperature climbs up to over 180 right after you shut engine off. When I kept engines running - this was not an issue, both were running equally 122F.
Engine that overheated peeing strongly, matter of fact better then the engine that isn’t overheating.
Any thoughts? Thanks !
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
16,150
Hi, I just started having this weird problem where one of the engines would start overheating after it was shut off. I was out fishing and constantly moving boat to get a drift so after couple of hours one of the engines beeped an overheat alarm. I tested few times and it would happen every time, temperature climbs up to over 180 right after you shut engine off. When I kept engines running - this was not an issue, both were running equally 122F.
Engine that overheated peeing strongly, matter of fact better then the engine that isn’t overheating.
Any thoughts? Thanks !
Peeing isn’t a good indication of internal flow. Some are plumbed separately from the cooling loop

Increasing temp at shut off would point to a “hot spot” within the cooling circuit.

Check the poppit valve
 

_vn_

Petty Officer 2nd Class
Joined
Apr 23, 2012
Messages
131
checked poppets on both engines - moving freely and no blockages.....
 

_vn_

Petty Officer 2nd Class
Joined
Apr 23, 2012
Messages
131
I ran the engines couple days ago at the dock, both engines ran fine, except the port one was slightly hotter when turned off but has not reached the temp over 172. I checked thermostats and the all look fine, no blockages. I also used a laser thermometer while running engines and after the shutoff. Both engines temeprature were similar - bottom cylinders 130 and top around 145-150
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
16,150
Then it may br the temperature sensor?
…or the wiring or gauge.

Run the boat to simulate conditions. Pull the wires off both sensors and measure the outputs.

Output (ohms) of both sensors should be very close, if not identical.

If the outputs are the same, pull wires from the back of gauge and run the test again.

If nothing turns up there, swap sensors to see if the problem follows the sensors.

If nothing changes with the swap, replace the offending gauge
 
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