1983 200hp Black max overheating at/over 4000rpm

[Draina]

Hey guys.

So I’ve got a 200hp 1983 Black max it’s setting off the overheating alarm if I sit on or go over 4000rpm.

It’s got a new impeller the power heads been rebuilt recently but before I bought it.I’ve just had the carbies rebuilt and done a service. It wasn’t overheating when I first got it but now seems to be getting more frequent.I don’t run thermostats and wasn’t running them before either but guessing this could be my issue? I’ve seen a lot of comments about not running them in these motors but then seen comments about other outboard about with them there’s not enough time for heat transfer but I did have it running for a while without issue. It originally started getting hot after doing a couple hoops or tight turns but would be fine holding wide open throttle but now gets hot if it’s cruising at 4K or more. Boat gets used in salt water. But flushed after each use. Motor does sit quite high on the transom so I have wondered if I’m sucking air through the factory intake but wanting to eliminate other possibilities before installing a low water pick up.

 

[Chris1956]

That motor has thermostats and a poppit valve. Thermostats cool the motor at low speed and the poppit opens to cool the motor at high speed. I would recommend you replace the thermostats, so the system is configured properly.

At about 2000 PM the poppit valve should open. You might inspect it and rebuild it. Poppit valves changed over the years, so make sure to get the right kit.

If that doesn't get it, your head gaskets could be leaking exhaust into the cooling passages. Since you have the power head rebuilt, you might torque the head bolts to spec, in the correct order, and see if that fixes it.

 

[Faztbullet]

You gotta run a t-stat or restrictor washer,,,cannot run with t-stats totally removed

 

[Draina]

What temp should the thermostats open at I’ve got some here that il test and try

 

[Faztbullet]

Around 150°

 

[Draina]

Hey guys. Just an update. Motor was pulling air. Taped and plugged the top 4 holes either side and installed a temperature gauge. Motor stays around 58c with a high of 65c. No thermostats.

Ran it serval times since plugging top 4 holes and no overheating issues at all.

 

[Faztbullet]

Gotta have T-stat or washer as cylinder can cold seize

 

[Draina]

What’s cold seizing?

 

[Faztbullet]

Cold seize is when the piston warms up faster than the cylinder .Piston expands and cylinder walls are overcooled causing clearance problem. Usually from the piston pin to skirt is what seizes as clearance is to small. You dont not want to scuff your cylinders as they are chrome plated and if damaged block becomes basically junk