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Old 12-11-2015, 07:13 PM   #1
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Perkins T6.354 Fresh Water Cooled Exhaust Manifold

I'm consolidating some discussions from various posts into a dedicated thread on converting the raw water cooled exhaust manifold to the fresh water coolant circuit. Some of the information is interesting on BoatDiesel.com but it doesn't really get into the details, and doesn't address running at WOT.

I have found four write-ups from people who have done it and they typically result in some overheating. In one case it was resolved by increasing the size of the heat exchanger.

The typical way is to use the ports at the freshwater pump that were designed for a cab heater and are commonly used to heat a hot water tank for the house. The original design is the water coming back would be cooler or possibly the same temperature. Using this flow results in hot water getting extra-hot, then going straight back into the engine.

I believe a better approach is to add a bung on the 2" pipe that takes hot water to heat exchanger. This is where the hot water is returned from the manifold. This way the extra-heated water goes through the exchanger before going back into the engine. It also increases the flow of coolant through the heat exchanger. The typical approach decreases the flow through the heat exchanger since the water pumped through the manifold goes straight to the pump intake.

Here are some diagrams. Does this make sense?

Thanks,
RR
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Old 12-11-2015, 08:01 PM   #2
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Most, or at least many marine diesels use a bypass loop going through the exhaust manifold, so even with tstat closed, wp pushes coolant through block head and mani in a loop. Then as tstat opens, some flow is diverted to hx, but mani still has flow driven by the dp across tstat. If you divert flow from mani right to hx, engine will subcool at low load and that is not good.
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Old 12-11-2015, 08:25 PM   #3
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That's a very good point. The only alternative I can think is to have a separate water pump that pulls from the cool side of the hx and returns to the hot side. I think the pressures would cancel each other and not alter the flow of the main coolant loop.
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Old 12-11-2015, 08:26 PM   #4
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RR

It makes sense that the engine HX would have to be larger when converting from RW to coolant cooled exhaust manifold.

If you could lay your hands on a Perkins Sabre engine flow chart you'd likely have the flow sheet you need. Mine are on the boat, left yesterday so now 1300 miles away. Boat diesel has them I'd guess. Try an internet search too. BTW I have only one RW pump, and a coolant pump of course. Works just fine.

I've got 2 new transmission RW coolers that should work just fine for that purpose.
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Old 12-11-2015, 11:36 PM   #5
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If you get stuck for parts, contact EJ Bowman.co.uk
They make the original equipment parts to marinize Perkins engines and they ship worldwide.
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Old 12-13-2015, 05:00 PM   #6
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Quote:
Originally Posted by sunchaser View Post
RR

It makes sense that the engine HX would have to be larger when converting from RW to coolant cooled exhaust manifold.

If you could lay your hands on a Perkins Sabre engine flow chart you'd likely have the flow sheet you need. Mine are on the boat, left yesterday so now 1300 miles away. Boat diesel has them I'd guess. Try an internet search too. BTW I have only one RW pump, and a coolant pump of course. Works just fine.

I've got 2 new transmission RW coolers that should work just fine for that purpose.
Good points. I would think the ideal flow is to keep the manifold in the loop while warm-up, then divert flow to the exchanger as the thermostat opens. I'll research the Sabre and try to find out if that's how it works.

I think with this engine's architecture there's no way to obtain this ideal. At WOT my EGT is 900+ F., so this is significant heat being dumped into the cooling system. While at cruise it's less than half this but still contributing heat.

I've scoured the Bowman site.

I think it might come down to some experimentation and see which setup works best for my boating style. With a semi-planing hull it's nice to get over the hump at WOT and boogie (well, 12 knots). Especially when transiting choppy areas, like crossing SF Bay when exposed to the entrance, and the passengers want to get past the chop as soon as possible.

I have just totally overhauled the fresh and raw water circuits and the cooling system running at highest efficiency. It is back together as stock (raw water cooled manifold) the temp stays solidly at 180, regardless of load. The manifold is cold to the touch, as are the jacketed parts of the elbow. Interestingly, the freshwater water return pipe from the HX is much colder than I would have thought. Water going into the exchanger is around 180 degrees and comes out well under 100.

My guess is with a very efficient cooling system there is adequate capacity with the stock HX. However that's not a fair test since every day both cooling circuits slowly become less efficient until the next major service. Since the raw water circuit loses it's efficiency the fastest, just getting the manifold into the FW circuit should increase time between overhaul (since there would be fewer component in the raw circuit). I'll definitely add the air charge cooler to the annual maintenance since that thing was a mess. Would be nice to convert that to a plastic housing since the cast iron creates a swollen scale.

Thanks for the advice and please keep it coming,
Robert
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Old 12-14-2015, 02:44 PM   #7
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Ideal Flow

I found this diagram on the web. Seems to confirm that the thermostat plays a part in coolant flow through the manifold.

The manifold requires constant flow, regardless of warm-up.

The engine needs to be a closed circuit until warm up.
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Old 02-09-2016, 11:19 AM   #8
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Ryan, Mine may have been one of the writeups on this conversion that you saw. I did mine at least a decade ago and have helped many others to do the same. I have had no ill effects from doing so and the faster warm-ups and higher temps at idle have more than likely helped my engine. Sorry I missed your original postings.
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Old 04-25-2016, 12:17 PM   #9
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Quote:
Originally Posted by Brooksie View Post
Ryan, Mine may have been one of the writeups on this conversion that you saw. I did mine at least a decade ago and have helped many others to do the same. I have had no ill effects from doing so and the faster warm-ups and higher temps at idle have more than likely helped my engine. Sorry I missed your original postings.
.?


Hi Brooksie

Could you help me out with a drawing?

I have twin T6-354's in my steel boat. I want to convert to keel cooling
and dry-stack exhaust. Solves some cold climate issues up here in Canada.
Would certainly appreciate a little guidance in this conversion.

Thank you.
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Old 04-29-2016, 01:42 PM   #10
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(when I saw this a minute ago there was a GIF showing the arneson drive. I guess it was an advertisement and is no longer showing. Sorry for the off-topic)

Interesting about the Arneson drive GIF. He used to launch his dual turbine-powered catamarans at the same marina where I kept my boat. At first it was interesting to watch him fly around north SF Bay at 160mph. However it turns out his visibility was not that great and I nearly got run over by him when I was out in my small zodiac. He was heading straight at me and I stood up and waved an orange life preserver. He made a distinct change in his course and ran through a bunch of birds sitting in the water. As I made my way in I could see the water littered with feathers and wing pieces.

Others had similar stories, and the wind surfers were concerned because when they're not up on the board they are almost invisible. This was over 20 years ago. He would also give demonstrations to prospective buyers. I saw Ross Perot take a ride, and there was a period when the military would come by. Amazing nobody was ever killed. We would have dredges leave steel bouys in the water at seemingly random places...
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