Mercruiser 5.0 overheating

[Oldone88]

Ok. I ordered the new T with the check balls. And I’ve also ordered a new sending units for the gauge and alarm buzzer. Hopefully everything will be in my Monday and I can do some testing.
thanks

 

[Oldone88]

Follow-up report.
installed new sensors which made it worse. What was supposed to be the correct sensor was showing about 120 on the gauge before starting.

started it and it went up to about 220 on the gauge in a few minutes. I was checking it with a laser pyrometer and the hottest reading I could find was on the head, about 180. T stat housing was about 160, risers about 80.

shut off and switched back to original sensor which brought the temps to about 170 at start (motor still warm). Idled it till it got near 220, checked engine with pyrometer, nothing above 180.
I tried bumping the idle a bit to lower the temp but couldn’t get it to come down much.

removed old T from T stat housing and installed the new one with the check balls.

engine was still warm when I fired it back up and the temp was around 220, but within a minute it started coming down and leveled off just a bit above 170. I revved it to about 1500 rpms for a bit, came down below 170.. idles it for about 5 more minutes, and it hovered around 170. This was all on a garden hose, so I’m assuming it might be even lower in the water..

I want to think everybody for their input. The questioning of the check balls cinched the deal. Hopefully I’ll have it in the water in the next few days for a true test.

 

[alldodge]

installed new sensors which made it worse. What was supposed to be the correct sensor was showing about 120 on the gauge before starting.

Could be a gauge problem also, but the sender doesn't seem correct.
Measure with ohmmeter when cold and as it warms up in pan of water

 

[Oldone88]

Followup: the check balls appear to have been the fix..i believe what happened was that when i moved to Florida in 03, i had an overheating issue with the boat.. My mechanic at the time, told me i needed a new thermostat housing due to corrosion, but that they didn't make them anymore, he told me he would find me one.. What he did, was install an older version T stat housing, that used the checks balls, but never installed the check balls setup.

I have fought overheat issues of some sort for several years.. Every time i brought up the check-balls to a mechanic i was always told that my year engine didn't use them, which is essentially correct.. I just had no idea i had the old style housing. This site helped immensely with guiding me to the problem, and its greatly appreciated..