1968 38 ft commander Starboard motor running hot self contained.

Delta T for HX and manifold/exhaust?

Could be something blocking some of the heat exchanger tubes. Seaweed, debris, impeller vanes,...

Does it run hot all the time or only under heavier load (on plane)? And how hot is hot?

It runs hot under heavy load. The motor was just rebuilt in 2023, the temperature gauge says 200 degrees I don't know if that is correct?

Such a common issue. Closed cooling was barely adequate when new. Do you have an infra red heat gun. Only way to diagnose. $25 at HF. Start there. Use the cooling diagram that is on the site here. Document both motors on the diagram. Some of us will be glad to assist when you have that data. Trust me. Many of us have been there. Otherwise you will just be throwing parts at it.

I just got done running the boat, the starboard motor says 175 degrees but when I running at 2900 rpms the gauge says 220.

We need some clarity here. Is the 175 also at 2900

When I running 2900 rpm on the lake its 220-230 degrees. Thank you. When I take the radiator cap off the antifreeze is circulating.

As scott says you need better data with an infrared gun. Three places to gun and report back:

1. at the thermostat housing

2. At the temp sender (front corner of intake

3. At the big hose on bottom of the heat exchanger. Do Not let it get over 200 if your gun is verifying!!! let us know what you found! Data is important

   
   

At the thermostat housing, 210 degrees, at the temp sender190 degrees, at the big hose 185 degrees.

All indications say Tstat is stuck or not opening all the way! However beware!! On 427 there is no replacement sealing ring (oring) that goes around the stat to seat into place for these. You really have no choice but to run open /no stat if you choose to. It will still come up to temperature under load and run much cooler but it will be running cool which isnt desireable for fuel burn efficiency . Unless someone has sourced the parts recently. You really are stuck. (No pun intended)

Could you make your own gasket? And Thank you. I met you once in Detroit at Keans marina at the Chris Craft rendezvous.

It is not really a gasket. It is a press in seal. Very strange set up. I need to look at my notes. I think I took mine to a bearing shop and got a replacement. You can take the stat out without damaging the seal unless it is so brittle.

Thank you.

I believe I found a seal from Bearing Headquarters also what temp thermostats? Dick Morland has a picture on the web sight the thermostat opening at 140 degrees. Thank you.

Chris used 140F claiming that was saltwater compatible.

Captain Michael ...... The correct t-stat for the Chris Craft 427 with closed cooling is 160 F which STARTS to open at 160 & runs at a nominal 180 F under load with correct impeller & cam wear plate installed & correct psi cap on reservoir coolant tank .

Tim

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Captain Michael ...... The correct t-stat for a raw water cooled Chris Craft 427 is 140 F which starts to open @ 140 F . & runs at a nominal 150 F under load . Remember that if you have a water heater plumbed into one of the engines cooling system that engine will run a bit warmer on temp under load .

Tim

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Thank you to every one for your help. I found 2 160 degree t-stats and 2 seals.

Michael, Which seal did you get from Bearing Headquarters? Part #? And the seals fit the 160 degree t-stats?? This info would be a great help to club members. Thanks!!