perkins engine advice wanted

[tony bolger]

Hi, I'm new to this so please be gentle, I have a 34ft cruiser that I have just spent 6 months refitting and bringing back to life, she was destined to be chopped up and dumped. I have never attempted anything on this scale before and I'm pretty proud of myself. She has an old 1960"s perkins engine, a 4108 I think, cooled by water drawn in from pipes under the hull, there is also a small header tank that I'm told should be kept topped up with water. At the moment the header tank is not connected to anything........ I need help, any ideas where this should be connected to? Any diagrams? I know almost zero about engines, I've tried online and asking around and all I have found is the header tank feeds water to a heat exchanger and then is cooled by the water sucked in from outside.......I think I understand the principal but don't even know what a heat exchanger looks like or where it may be found, any and all help would be very well received.

[DeepFrz]

Originally Posted by tony bolger

She has an old 1960"s perkins engine, a 4108 I think, cooled by water drawn in from pipes under the hull, there is also a small header tank that I'm told should be kept topped up with water. At the moment the header tank is not connected to anything........

Some pictures of what you have might help. There are lots of pictures of 4-108s on the forum with pictures of header tanks and heat exchangers. Doing a Google Custom search (under the search button) should get you all kinds of information. Try it and then if you need help post some pictures and ask a question.

What the hell do you mean by your statement above about water drawn in from pipes under the hull?

What is your boat made of?

[Capt Phil]

Your heat exchanger is like the radiator in your car. It circulates fresh water through the water jacket of your engine to keep it cool. It is a closed system. The raw (sea or lake) water is pumped through the heat exchanger to keep the cooling water in the heat exchanger cool just as air cools your radiator. There are 2 water pumps, one to pump your coolant around your engine to cool it off, the other to pump the raw water through your heat exchanger. You might have a closed system of cooling made up of pipes that run longitudinally along your hull for cooling your fresh water coolant. In that case you will not be constantly pulling raw water out of the ocean or lake through your heat exchanger. You may also have only one pump to run the cooling water through the externally hull mounted piping and the engine water jacket. Haven't seen this set up for some time but the old Easthope engines had something similar. If you are doing a rebuild on your engine, you should replace or rebuild both water pumps. In addition, your heat exchanger will have a 'pencil zinc' to act as a sacrificial zinc to avoid salt water eating up your heat exchanger. If the has been let go by PO, you may need to replace your heat exchanger. Once you have rebuilt your water pumps, you should add the same type of impellers to your spares list to have extras as they tend to wear out and the fins can break off and plug your heat exchanger. That is about all you need to know about your cooling system. I've tried to make it simple so you can understand it and do the repairs yourself... hopefully someone else can add to what I've started. Cheers, Phil

[Cheechako]

water drawn in from pipes under the hull? You mean what's commonly called a "keel cooler"... a pipe or two outside the hull that cool the engine coolant...?

[Lancerbye]

By you saying that the cooling water comes from pipes under the boat it sounds as if you have a keel cooler system which were very common on trawler style fishing boats. This is a closed system that has no external raw water entering your boat. These set ups are basically done similar to a automotive system. There is no secondary pump for raw water and no heat exchanger. The coolant is simply circulated through the engine cooling the exhaust manifold in the process run through the keel cooler and back to the engine. All you need for this is an expansion tank which can be made of plastic and connected to a small hose connection which is located just below the pressure cap filler. (small hose) When I had one of these I kept the tank above the engine and always have coolant in it as in a car.

[Capt Phil]

Cheechako and Lancerbye are correct... had a bit of a brain fart which is becoming more and more frequent at my age... thanks, guys, cheers, Phil

[tony bolger]

The boat was built for use in- fresh water, norfolk broads, uk. So far I've discorvered the raw water goes through a filter before going to a heat exchanger to cool the fresh water from the header tank.
The raw water, which is constantly replenished is then discarded via the exhaust, the fresh water stays in the system and is topped up via the header tank.

[atoll]

Originally Posted by tony bolger

The boat was built for use in- fresh water, norfolk broads, uk. So far I've discorvered the raw water goes through a filter before going to a heat exchanger to cool the fresh water from the header tank.
The raw water, which is constantly replenished is then discarded via the exhaust, the fresh water stays in the system and is topped up via the header tank.

that is a normal closed system for a boat.
the water pump on the front of the engine circulates the antifreeze coolant via the header tank through the engine.

the impellor pump draws in raw water via the filter,through the heat exchanger element in the header tank,then out the exhaust.

no keel pipes i would think

[tony bolger]

There are two pipes, one either side of the keel, everything on the raw water appears to be working, just need to work out how to connect the header tank, I did not see any open connections or unused pipes and was hoping someone out there may know what to do, gonna need to employ an experienced mechanic when I get more funds, thus far I've been able to it all myself with guidance from folk online.

[brutb]

Tony, you might ask someone on another boat to give you an idea of how the expansion tank is routed and look at his system to get a physical idea of what your system should look like. Most likely asking for a little assistance can be a good way to see how others have maintained or restored their boats. And like you they will be happy to spend hours explaining how and why all was done. I no I do...hehe

[tony bolger]

That's good advice but for the' nearest vessel like ours is 300 miles away, hence the online route.

[Lancerbye]

Post 7 and post 9 don't add up. Post 7 describes a raw water to exchanger system and post 9 describes a keel cooler system. I wonder if at some point in the boats history the boat was converted from one type to the other. At this point I think pictures are needed to verify what is really being used. The keel cooler may have been discontinued when the boat was used in fresh water, or you have built in redundancy.

[tony bolger]

The boat was built for a hire company based on the norfolk broads circa 1969, I will post some photos soon

[Cheechako]

Google 4-108 on line and then add the word "pictures". You should be able to see some setups there. here's one example: