PCM 351W fresh water cooling (FWC) |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Wilhelm where does is hose that feeds the T come from?
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Wilhelm Hertzog
Senior Member Joined: June-14-2014 Location: Cape Town Status: Offline Points: 334 |
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Points taken, thanks! It is indeed an automotive carb, but it has been fitted with J shaped float bowl vents. Not always simple/cost effective to get OEM marine parts for old engines in South Africa... As to the distributor: does that unconnected vacuum advance canister potentially cause ignition timing issues? |
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1982 Ski Nautique PCM351W RR II Velvet Drive 10-17-003 1:1 II PerfectPass Stargazer
Do not go gentle into that good night. Rage, rage against the dying of the light. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11046 |
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As far as the distributor, it more a matter of spark protection.
Where the advance mechanism goes through the distributor there's an opening that gas fumes can pass through and get into the distributor if you have a fuel leak. The fumes meet the spark in the distributor and you have an explosion that is not contained in the distributor because of that open unprotected path. The marine version has no vacuum advance and the opening is blocked off but there are a couple of vent holes in the body of a DUI HEI marine distributor that have brass screens in them which keep the explosion contained inside the distributor. The gas fumes can still get in if you have a leak but like mentioned above the screens prevent the internal explosion from getting outside the distributor so it keeps the fumes in the engine compartment from exploding. The distributor may be damaged internally, but you won't be in an exploding boat. It works on the same principle as an old miners lamp Here's a link down below to a thread by somebody who "converted" his Chinese distributor. In his mind it meets USCG requirements The typical factory job has 2 layers of screen per vent hole, not 1 like he did. I think there's a reason for that Lots of people have survived for a long time without USCG approved stuff on their boat, but it just takes that one bad day to change all that. link Some later marine certified distrihbutors are well sealed with no openings for fumes to get into the distributor. By the way, is your engine normal automotive rotation or if it's reverse rotation, did you have some machine work done to adapt a reverse rotation gear to that distributor? |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21169 |
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Just 1 connection, rather than in/out? Risers are dry? |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11046 |
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It seems to me that the manifolds and risers are raw water cooled.
Instead of the raw water going in the front of the manifold, it goes in the rear and up through the riser and out the back of the boat. |
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Wilhelm Hertzog
Senior Member Joined: June-14-2014 Location: Cape Town Status: Offline Points: 334 |
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Correct. |
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1982 Ski Nautique PCM351W RR II Velvet Drive 10-17-003 1:1 II PerfectPass Stargazer
Do not go gentle into that good night. Rage, rage against the dying of the light. |
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Wilhelm Hertzog
Senior Member Joined: June-14-2014 Location: Cape Town Status: Offline Points: 334 |
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Reverse rotation. I can't recall if the PO installed the distributor or if it was done by the guys who rebuilt the motor for me. I suspect there was some machine work involved, yes. |
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1982 Ski Nautique PCM351W RR II Velvet Drive 10-17-003 1:1 II PerfectPass Stargazer
Do not go gentle into that good night. Rage, rage against the dying of the light. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11046 |
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That would be a FWC half system or a closed cooling half system |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21169 |
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I’d like to see how the cooling passages line up on those risers. Never seen that style before, though they are handsome. Manifolds look like normal PCM. Gasket for reference: https://www.skidim.com/images/RM0002.jpg |
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Wilhelm Hertzog
Senior Member Joined: June-14-2014 Location: Cape Town Status: Offline Points: 334 |
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No, neither the risers nor the manifolds are the standard PCM Ford ones. Off a GM motor IIRC, with a bit of adaptation to fit them to the Ford block, and custom cut gaskets. I have had this setup since buying the boat - seemingly no issues. |
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1982 Ski Nautique PCM351W RR II Velvet Drive 10-17-003 1:1 II PerfectPass Stargazer
Do not go gentle into that good night. Rage, rage against the dying of the light. |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3357 |
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I don't see any gazintas
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Wilhelm,
Getting back to the high temp issue, if your bucket test proves the RWP is doing the job AND if your manifolds are running cool, I'd see if a raw water restriction to the manifolds will do anything. The restriction may put more raw water through the heat exchanger to make a difference. |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Tim the raw water from the hull pickup follows the normal PCM path until it exits out of the Sherwood pump. Instead of running to the thermostat housing it goes to the heat exchanger cooling the block coolant then exits out of exchanger via 1 outlet into that T and then like a raw water cooled engine into each exhaust manifold through the risers and out. They put the water in the back of the manifolds only because the way the exchanger is mounted its outlet is near the bellhousing thus keeping the hose length short. The only real difference here is that he has the exchanger mounted across the rear of the engine rather than PCM's length wise mount behind the Sherwood pump. This is why it is called a half system in the sence that only the block is protected- the manifolds still being raw water. I'm not sure but I think a full system has the manifolds cooled by the block water with block off plates at the manifold to riser joint but the risers are still cooled by the exit of the raw water |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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I'd like to know where the water comes from before that T to the manifolds i.e. Is the raw water making a full pass through the exchanger not tapped off half way down it or something. I just cannot see where it is coming from in the pictures |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3357 |
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I think the vacuum advance is inhibiting water flow
What happens if you remove the statat? that could tell you if you have a enough heat transfer available in the system, and suggest which water circuit the problem is. |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21169 |
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I know how it’s supposed to be plumbed, I’m asking how he has it plumbed since there appear to be a number of inconsistencies to go along with the described cooling problem. |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Oh - never mind. According to the Shamrock guys these parts can be mounted just about anywhere but they are not to concerned at how anything looks,just that it does the job.
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JoeinNY
Grand Poobah Joined: October-19-2005 Location: United States Status: Offline Points: 5698 |
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So if it is reverse rotation it may actually need a bidirectional circulation pump to work correctly, Something has to move that water through the heat exchanger. Considering the number of automotive parts needed to make things work over there I would check to make sure a standard rotation automotive pump wasn't used.
It is important that the heat exchanger is plumbed in the correct location to get full capacity out of the heat exchanger but near as I can tell it is. I would love to see how they got a chevy manifold to fit a ford. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11046 |
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I figure if you start with a marine manifold for a 5.3 or 6.0 Chevy, a sandwich type adapter plate that would probably have to be "home grown" would make this halfway easy Here'a a picture of a 6.0 Chevy exhaust gasket and a 351w exhaust gasket, you'll have to visualize the adapter plate. I think a machinist in South Africa or anywhere else could whip up a couple of those adapters fairly easily |
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Wilhelm Hertzog
Senior Member Joined: June-14-2014 Location: Cape Town Status: Offline Points: 334 |
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The pictures below shows the detail. Raw water leaves the heat exchanger to the T circled in blue. From there I assume it is supposed to flow to the next T circled in green (more clearly visible in the second photo). This T sends water to the exhaust manifolds and the trans oil cooler. From the trans oil cooler, water is sent to a heater I have mounted in the front of the boat. Water from the heater comes back to the blue T via the red elbow connector. Upon looking at this setup, a few things here don't make sense to me the way the guys who did the installation for me did things: 1. Water coming out the heat exchanger and water coming back from the heater will be 'fighting' each other at the blue T, not so? Surely this will create flow issues somewhere? The heater never heated up properly despite the engine running hot - a symptom of this perhaps? 2. Having raw water pass through the heat exchanger before going to the trans oil cooler must surely mean the trans oil cooler is not getting particularly cool water? The standard placement would be before the heat exchanger, right? Even though this means the trans oil cooler is putting some heat into the water going into the heat exchanger? Thanks for any help here! |
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1982 Ski Nautique PCM351W RR II Velvet Drive 10-17-003 1:1 II PerfectPass Stargazer
Do not go gentle into that good night. Rage, rage against the dying of the light. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11046 |
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#1 Why not keep it simple till you get things figured out and disconnect the heater or at least isolate it?
#2 The transmission cooler is usually the first place the cool water goes. Some setups have the cooler before the raw water pump and others have it after the raw water pump but in either case, the first thing to get cooled is the transmission fluid. In the link is a "typical closed water cooling half system" like yours. It's for an inboard outboard and shows the raw water going through a power steering cooler after the transmission cooler, but you'll see the typical flow path. link |
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outerbanked
Senior Member Joined: July-27-2017 Location: seattle Status: Offline Points: 104 |
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I know you have a few issues you are working on. Agree with KENO to simplify what you have until it is working. Get an infrared temp gun.
1. Create a block diagram of your system. 2. Your heater should be on the antifreeze circuit. (Warmer heat, ability to help cool your engine using it). 3. Have you been able to verify both of your pumps are working? a. Part number for your engine mount water pump is a bi-directional marine pump? b. Raw water pump has sufficient flow. 4. Your path should be water inlet, strainer, trans cooler, raw water pump, heat exchanger, tee, exhaust manifolds. Pg55. https://www.marinepartsguys.com/wp-content/uploads/ILLUSTRATED-PARTS-MANUAL-PCMcompressed.pdf |
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Wilhelm Hertzog
Senior Member Joined: June-14-2014 Location: Cape Town Status: Offline Points: 334 |
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Should I replace the plastic tees and elbows in the system with brass while I'm at it? Or is plastic fine?
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1982 Ski Nautique PCM351W RR II Velvet Drive 10-17-003 1:1 II PerfectPass Stargazer
Do not go gentle into that good night. Rage, rage against the dying of the light. |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Up to you if you change them Correct Craft seems that now days they only use that grey plastic. If your in salt,which I think the reason you have the fresh water cooling, and you want to change you don't want brass you'll want bronze
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Wilhelm Hertzog
Senior Member Joined: June-14-2014 Location: Cape Town Status: Offline Points: 334 |
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I have a dripless shaft seal. Where in this path should the water feed to the shaft seal ideally be located? And is it okay to run the engine in gear on a flushing connection with a dripless seal (bearing is lubricated with the water feed?) or will that destroy the cutlass bearing? |
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1982 Ski Nautique PCM351W RR II Velvet Drive 10-17-003 1:1 II PerfectPass Stargazer
Do not go gentle into that good night. Rage, rage against the dying of the light. |
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Wilhelm Hertzog
Senior Member Joined: June-14-2014 Location: Cape Town Status: Offline Points: 334 |
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Finally figured out what manifolds and risers I have: link. They are the Chevy ones though, hence the adapter plate as mentioned in some of the later posts. Interesting mix I have here: New Zealand manifolds on an American boat in South Africa. |
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1982 Ski Nautique PCM351W RR II Velvet Drive 10-17-003 1:1 II PerfectPass Stargazer
Do not go gentle into that good night. Rage, rage against the dying of the light. |
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Wilhelm Hertzog
Senior Member Joined: June-14-2014 Location: Cape Town Status: Offline Points: 334 |
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Okay, so a follow up after doing the following over the past few months:
Engine temps were fine on a hose in the garage (I could not run it for extended periods on the hose though), but when I took it out for its first water test a few days ago, engine temperatures were still running up (to about 190 - and rising - on my IR temp gun) when the motor is at idle for long periods of time and when coming down to idle rpm after running at speed. At speed, and also when revving the motor in neutral to about 2,000 rpm the engine temp drops quickly back to normal (170 and below - I have a 170 deg. thermostat). So it seems to me the raw water pump is not circulating enough raw water through the heat exchanger at idle speeds. Is this a common problem with fresh water cooled setups like mine? I imagine not. Other than replacing the impeller and seeing if that gives me (even) better results on a bucket test, I can't think of anything else to improve the situation. Any suggestions?
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1982 Ski Nautique PCM351W RR II Velvet Drive 10-17-003 1:1 II PerfectPass Stargazer
Do not go gentle into that good night. Rage, rage against the dying of the light. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Wilhelm,
Did you ever investigate potential issue with the size of the heat exchanger?
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Wilhelm Hertzog
Senior Member Joined: June-14-2014 Location: Cape Town Status: Offline Points: 334 |
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No, I didn't. It is the OEM heat exchanger from PCM, and as best I can tell nothing in my engine should make it need a larger heat exchanger. So I figured I'll revisit that as a last resort if I've exhausted all other troubleshooting options.
At the moment I'm leaning towards replacing the impeller to see if that makes a difference. The impeller looks fine when inspected through the pump outlet, but I'm not sure how old it is (which probably means it's quite old), and maybe it's bucket test performance is not quite as good as it should be, which just may be enough to tip the engine into overheating and not maintaining a stable temperature? If replacing the impeller doesn't help, then maybe there's an issue with my circulation pump not circulating water through the engine well enough? |
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1982 Ski Nautique PCM351W RR II Velvet Drive 10-17-003 1:1 II PerfectPass Stargazer
Do not go gentle into that good night. Rage, rage against the dying of the light. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11046 |
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Logically, if you have no idea what the Raw Water Pump impeller or the inside of the pump looks like or how old it is, that would be a good place to start.
You have a bunch of money invested in new cooling system parts, why not spend a little more on a new impeller? The worst thing that can happen is that you'll have a spare impeller and that's not exactly a bad thing. Here's a link to a Sherwood catalog that has impeller performance curves on page 10. Your G20 or 21 pump with a 9959K impeller should empty a 5 gallon bucket in under a minute at about 1000 rpm if you want to compare your test results to their graph. If you have a different Sherwood pump, you should be able to find it's info in the same catalog. Then you could figure out what you have for an engine circulating pump as the next step if necessary
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