1974 Tri-Hull 18’ with Mercury 188 hp - overheating

[LOZ James]

Yes, this near-50-yr-old “Grandma Cobalt” still runs and she has been running really well, except lately. After launching and running for 5 minutes or so, engine overheats. No digital temperature indicator - just a primitive display with green, yellow, red and an arrow. Need some guidance on most probable causes and suggested actions, while refraining from any jokes. Thanks!
James

[Big Block Power]

Impeller and tstat. Plugged intake?

[bruceb58]

When was the last time the impeller was changed? If you don't know, change it. Needs to be changed every other year.

Also, add a real temp gauge. Besides oil pressure, a very important gauge.

[AsLan7]

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Hey James. So glad you found us!

As mentioned above... the impeller, thermostat, or something covering the outdrive intake are your most likely culprits. Check those before exploring further.

Any pics? We love them here.

And welcome aboard mate!

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[Lockey14s]

yup. Start with the impeller and go from there

[LOZ James]

Thanks all ... it was indeed the tstat!

[AsLan7]

Thanks all ... it was indeed the tstat!

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Sure thing buddy...and all we ask for is a pic or two in return.

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