Perkins with a dead heat exchanger

[TonyMS]

A neighbour in our yard in Greece has an elderly Morgan 33 with a Perkins engine - probably a 4-108. It is fresh-water cooled, and the heat exchanger has expired. As a temporary measure he has reworked the plumbing to route seawater through the engine, and it appears to work fine.
My questions are: can he/should he continue to run with seawater, or will he have significant corrosion problems? And if not, where can he get a new heat exchanger?
He comes from Germany, which is why I am asking these questions on his behalf.

 

[lusitano]

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[LittleSister]

As lusitano implies, replacement heat exchangers for the 4-108 (and some other Perkins models) are made by Bowman, and available from ASAP and other retailers.

I doubt he would have very significant corrosion problems running seawater direct through the engine, though I don't know for sure, but I expect he will quickly have problems with the cooling passages becoming blocked with scale. A seawater engine has to run cooler than a freshwater one, because at higher temperatures the seawater creates scale at a much faster rate. The ability to run hotter - and therefore more efficiently - is one of the advantages of an indirect (freshwater) cooled engine. So it should at least be fitted with a different thermostat to run the engine cooler.

For example, there are two different thermostats available for my Bukh engine, depending on whether it is direct (seawater) or indirect (freshwater) cooled. The thermostat for the direct (seawater) cooled version runs the engine at 50 to 75 degrees C, and the indirect (freshwater) cooled one runs at 70 to 95 degrees C. The Bukh temperature gauge has two different scales (and 'overheat' warning levels) marked for the two types of cooling system.

The Bukh seawater pump also has about a 50% higher flow rate in the indirect (freshwater) cooled version, 36 - 42 litres per minute, than the direct (seawater) cooled version's 24 - 30 litres per minute. (The two versions use the same basic pump, but fitted with different cam rings.) I don't know whether the Perkins has differential seawater pump rates, or whether or to what extent any difference would be significant.

 

[TonyMS]

As lusitano implies, replacement heat exchangers for the 4-108 (and some other Perkins models) are made by Bowman, and available from ASAP and other retailers.

I doubt he would have very significant corrosion problems running seawater direct through the engine, though I don't know for sure, but I expect he will quickly have problems with the cooling passages becoming blocked with scale. A seawater engine has to run cooler than a freshwater one, because at higher temperatures the seawater creates scale at a much faster rate. The ability to run hotter - and therefore more efficiently - is one of the advantages of an indirect (freshwater) cooled engine. So it should at least be fitted with a different thermostat to run the engine cooler.

For example, there are two different thermostats available for my Bukh engine, depending on whether it is direct (seawater) or indirect (freshwater) cooled. The thermostat for the direct (seawater) cooled version runs the engine at 50 to 75 degrees C, and the indirect (freshwater) cooled one runs at 70 to 95 degrees C. The Bukh temperature gauge has two different scales (and 'overheat' warning levels) marked for the two types of cooling system.

The Bukh seawater pump also has about a 50% higher flow rate in the indirect (freshwater) cooled version, 36 - 42 litres per minute, than the direct (seawater) cooled version's 24 - 30 litres per minute. (The two versions use the same basic pump, but fitted with different cam rings.) I don't know whether the Perkins has differential seawater pump rates, or whether or to what extent any difference would be significant.

Two very helpful replies. Thank you, I'll pass them on.

 

[Refueler]

As long as the routing is correct and he swaps out the thermostat for a colder version - he should have no problem at all.

The Perkins 4 series .... 4-99, 4-107 and 4-108 are designed to run with either raw or indirect cooling. The main aspect is the thermostat needs to be changed.

Why ? With FW indirect - the temp is higher to reach optimum running temp ... the FW is free of satls etc and therefore does not drop out salts etc. into the water channels. The 'Antifreexe / Coolant' will have agents in that look after this anyway. 65 - 93 C
But with Raw water cooled - the temp needs to be lower to avoid salts being deposited out and over time clogging water channels. Max 60 C

Perkins Workshop manual : page M2

My 4-99 had exactly same problem and we removed the HE and reverted to direct raw cooling. When I replaced the 4-99 with the 4-107 - we did the same there ... and actually removed the thermostat (note that it needs to be checked on the 4-108 whether thermostat can be removed - as the 4-108 had a change in design during its life from plain flow - to thermostat / pressure relief valve flow ... again Page M2).

Conclusion : Advise the German chap to swap his thermostat to a 60C version and enjoy the raw cooling !!

Of course any winterising for anyone doing similar in colder climes - means a good system of flushing / antifreeze through engine on lay up.

 

[billskip]

And exhaust cooling?

 

[Refueler]

And exhaust cooling?

The exhaust is raw water cooled anyway ... so ???

 

[billskip]

The exhaust is raw water cooled anyway ... so ???

Well I assumed (never assume!!) that the indirect heat exchanger was leaking and had been removed.
As the raw water passes through the hx its then combined with the exhaust gas and cools the exhaust pipe and muffler..so was wondering how the exhaust was now being cooled...

 

[rogerthebodger]

My perkins 4 236 has a homemade combined indirect engine heat exchanger and expanse cooled manifold then raw water feeds into the injection elbow

Some have a freshwater heat exchanger where the raw water cools the freshwater and the exhaust gasses/exhaust manifold

I would remove the heat exchanger and pressure test it and see if it can be welded of if its the inner casing see if it can be replaced.
I have delt with Bowman direct and found then very helpful

 

[vyv_cox]

Well I assumed (never assume!!) that the indirect heat exchanger was leaking and had been removed.
As the raw water passes through the hx its then combined with the exhaust gas and cools the exhaust pipe and muffler..so was wondering how the exhaust was now being cooled...

In exactly the same way. From cold start, water passes through the bypass and out through the exhaust via the elbow. Once the engine is up to temperature the thermostat opens, simultaneously allowing water to flow through the engine and closing the bypass. Water leaving the engine flows to the elbow and exhaust.

 

[Refueler]

Well I assumed (never assume!!) that the indirect heat exchanger was leaking and had been removed.
As the raw water passes through the hx its then combined with the exhaust gas and cools the exhaust pipe and muffler..so was wondering how the exhaust was now being cooled...

Actually just gone back to the manual ..... the raw water system draws seawater and then to exhaust jacket .. from there into the front of the cylinder block.. round the engine and then exits via the exhaust.

The Heat exchanger system revises that by supplying the coolant to exhaust jacket - round engine and back to Heat exchanger. The raw water cooling the HE passes through HE and exits via the exhaust.

In effect - the route of cooling water for exhaust and engine is similar .. the difference being whether coolant is closed loop with HE or non closed loop raw. The pump used to feed engine etc is same ... but of course an additional pump is needed to pump the raw water through the Heat Exchanger.

 

[Refueler]

When Alan converted my 4-99 and later the 4-107 ... he just removed the useless HE ... extra pipes / pump and basically fed the raw water to the impellor pump - which then fed straight into the jacket cooling etc.