[C38] How do I tell if my heat exhanger is not working?

[Tom Troncalli]

The original 2" heat exchanger on the 5424 was marginal in the best of 
conditions but with any debris or warm sea water environment the engine 
will overheat.  I have seen the 5424 overheat on a relatively new boat 
going across the Florida straight to Bimini.

I kept my Catalina 38 in Tampa bay and even with the engine flushed and 
using clean antifreeze water, the engine would run on the hot side in 
Summer when the bay was warmer.

I made a 3" exchanger for my 38 and never experienced overheating again.

Prestone makes an engine flush kit that puts an elbow in a coolant hose 
from the engine to the heat exchanger which allows easy flushing of the 
engine and also an easy way to "burp" the engine to remove air in the 
system.  This kit is cheap and works well with any boat, upgraded heat 
exchanger or not.

With this kit you can put the chemical flush in the engine, run it to 
clean up the engine, then use a city water hose to flush the residual 
cleaner from the cooling system. We first drained the engine into a 
bucket to remove as much of the cleaning solution safely from the boat 
as possible before we used the city water flush with the intention of 
keeping as much of the flush chemical from exiting through our bilge 
pump into the harbor.

Flushing probably eventually helps any engine but on the 5424 nothing 
beats a larger heat exchanger.  The original 2" exchanger just could not 
handle 24hp except in ideal conditions.  With a thermostat controlled 
engine, it is better to have an exchanger larger than needed but not 
smaller.

That's my experience anyway.

Tom Troncalli
Previous owner #95





On 8/1/2015 11:29 PM, 1derful at comcast.net wrote:
>
> Hello,
> My Catalina has been overheating.  Universal Diesel 5424.
> I removed the thermostat........it was corroded and wrapped with debris.
> I removed and cleaned the internal water pump.  Also lot of debris.
> Put hose in engine.  Water didn't flow but eventually it did.  More 
> debris.
> now when I run the engine it is cool until I put on the radiator 
> cap..........then it gets too hot and loses water.
> Any thoughts?
> Patrick
>
>
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