Perkins 4-108 Water heater plumbing

[forsailbyowner]

Thats the way it was set up when I bought the boat. Its the original water heater, as I mentioned earlier it is too big to get in or out anywhere, must have been put in during construction. Im assuming thats how morgan set it up at factory. But we all know about assumptions.

[phorvati]

How long does it take for water to get hot? Does it ever get hot? Do you need to be under way? can you just idle at anchor?
My engine reaches 180F at anchor idling. I've tried numerous plumbing options with water heater (6 Gal Seward products), none of which are satisfactory. Here is what I tried and my findings:

Option 1: Use Ports recommended by manufacturer, the ones in the head to feed the waterheater. One behind thermostat housing and one to the left of the thermostat housing. Observation was that at water heater inlet, hose does not get warm to the touch. Seems like there is air trapped and adding antifreeze via radiator cap on the exhaust manifold does not help. Also seems like there is barely any flow of antifreeze in this loop. Most of it goes via the 1-1/4" loop and the heat exchanger. Result was 2 hours at idle with no hot water.

Option 2: Tee off 1-1/4" heater hose between exhaust manifold and heat exchanger with 1-1/4"x1-1/4" x 5/8" copper barb tee fitting, feed the 5/8" hose to water heater. Feed 5/8" output of waterheater back to the block inlet just below alternator via another 1-1/4"x1-1/4"x5/8" tee.
10 hours of motoring and water was not warm. There seems to be no flow of hot antifreeze via the 5/8" route. All the antifreeze goes via heat exchanger and 1-1/4" route.

option 3. Use oil cooler to make another antifreeze loop between water heater, oil cooler and use separate jabsco pump to circulate antifreeze. Idea came from seeing how hot oil filter and oil hoses get. So far I got water to be luke warm after 2 hours at idle. Doesn't seem like oil has enough heat capacity to heat the water that way in reasonable time.

I am new to diesels so therefore the experimentation. But with my old atomic 4, I plumbed water heater directly inline between exhaust manifold and heat exchanger forcing all of antifreeze through waterheater and water was scorching hot after 1/2 hour of idling. This is not an option with diesel as that loop is 1-1/4" ID and water heater is 5/8".

[DeepFrz]

phorvati, do you realize the last entry before yours was in 2008???

[phorvati]

i see, I wasn't sure if it makes sense to start a new thread?

[roberttigar]

I realize this an old thread...I'd like any data avail on the best way to plump in the cvoolant lines from a 4-108 to the wwater htr.
A fitting near the thermostat seems to be the consesus for 1 end.
Then it gets a bit fuzzy.

Anyone suggest where to attach ther other hose to minimize overheating?
Bob

[DougR]

Here is how it was done on an engine that I had, and the same as mentioned earlier in the above thread....

- Outlet to the hot water heater- come out of the head on the threaded fitting just to the rear of the expansion tank. Normally this fitting contains the temp gauge sender, so the sender is removed and installed in a "T" where it still feels continuous flow. The other side of the "T" is sent thru a 1/8 or 3/16" restriction and then to the hot water tank. The advantage of using this source is that it flows some water to the hot water heater regardless of whether the thermostat is open or closed.

- return from the hot water heater- there was a fitting installed in the line between the outlet of the heat exchanger and the inlet to the oil/ gear box coolers. This location feels suction from the circulation pump, so the pressure in the cylinder head and the suction from the circ pump ensures circulation thru the hot water heater. If you don't have the factory fitting in this copper pipe, just make a "T" in the hose on the outlet side of the heat exchanger.

DougR

[roberttigar]

Thanks Doug, that's exactly the information I needed. I am going to add 1 more item to the run-a second tee so that I can install a petcock to aid in draining off any air out the system. The water lines to the heater tank are 5/8". Wil the engine run cooler if the lines are smaller dia? Bob

[DougR]

I think it's best to stay with 5/8 hose to keep back pressure in that loop at a minimum. But you will note that I mentioned a restriction in the hot water outlet from the head. You don't want too much flow in the hot water heater circuit because that circuit bypasses the engine heat exchanger. When the water in the hot water tank is cold, the coolant flowing to the tank releases a lot of heat into that tank, but when the tank water has heated up, very little heat is released into the water, and so that hot coolant returns to the engine. This can cause the engine to run warm if there is too much flow bypassing the heat exchanger....hence the restrictor.

You can put a "T" into the water heater circuit to aid in air bleeding, but if the hot water tank is below the level of the engine expansion tank, it isn't necessary. The system will self bleed just fine.

If the hot water tank is above the engine expansion tank you should really have a remote expansion tank to allow complete air purge in the coolant system.

DougR

[roberttigar]

My engine, and many 4-108's tend to run hot if you try to push it towards 2000 rpm's-at least sailboats with cruising props. Wouldn't I be better off minimizing the flow to the hot water heater so more flow runs thru the Heat exchanger? Bob

[DougR]

If you have a restriction of 1/4" to 5/16" in the outlet to the hot water heater, that's plenty.

The inherent problem with the rear mounted heat exchanger was that it was just too small for the amount of heat it needed to reject. Originally, I had the same problem with the engine that I had. The factory HE had a tube bundle that was 3" diameter X 9" long. I had a HE made with a 3 " X 12" tube bundle that fit in the same location as the original with just a minor hose change. This HE had about 33% more tube area and I never had a problem with overheating after that, even in the warm water of the Chesapeake Bay. I propped the engine so the max. RPM was 3400, and I could run all day at 2800 without problem.

DougR

[roberttigar]

Yes, I have read your old posts with interest. 1 of these days I am going to do that. Sen-dure is almost in my back yard. But for now I am ok. Unless I am running against a strong wind or current I can do 6 knts. at 1800 rpm and thats as fast as the boat will go.

I'll use 1/4" pipe off the front feed and keep the hose at 5/8". Wont be a problem with the eturn line feeding into the Crazy Tee after the oil cooler with a 5/8 hose?
Bob

[DougR]

Not sure what the "crazy T" is, but you should be OK returning anywhere in the return circuit from the HE to the block.

I think the factory returned between the HE and the oil cooler because that's where the best accessibility is.

DougR