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Old 02-25-2014, 11:16 PM
sail_flathead_lake sail_flathead_lake is offline
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Electric FWC questions on early model motor

Hello all,

I recently bought an electric FWC kit from Indigo for the usual reason - no room for Don's shaft-mounted pulley in front of the motor. Sorry Don - I promise I'll be spending some money with you very soon!

I know that there are a million ways to set these systems up, but I have two particular quandaries:

1. I have heard the pluses of the Thatch modification (coolant exits the forward end of the exhaust manifold instead of the aft), and I agree with those arguments. The Indigo instructions recommend it. However, on early model motors the coolant passage between head and exhaust manifold is a cast iron u-shaped pipe visible in the lower right hand corner of this photo:

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If I remove this, will I find a tapped hole underneath it? If not, I don't think that this mod is worth removing the head to tap an NPT fitting. Even if there's a tapped hole under this u-shaped pipe, I'd have to loosen two head nuts to make the switch to a brass nipple, and I'm worried about the head gasket seal if I do this. Is it worth it? What would you do in this situation?


2. Most people seem to use the electric pump for the fresh water and the mechanical pump for the raw water. My early model motor is a really early model, and has the gear style water pump:

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Some say this pump is great, but only if there's no sediment flowing through it. This argues that I should use the gear pump for the 'fresh' water (antifreeze). Others mention that because there's a stuffing box with the pump it will drip a little under normal operation. Not wanting coolant dripping into the bilge, this argues for using the electric pump for the antifreeze. Lastly, when it comes to winterizing, the electric pump seems like the winner - just turn it on with a switch (engine doesn't even have to run) to draw antifreeze into it and the rest of the raw water system through a Y valve on the intake. Any comments here? I think that I can catch any drips from the gear pump with an oil spill mat under the engine (something I'd use anyway), so I'm not too worried about coolant dripping into the bilge. Plus the existing pump is hard-plumbed with copper pipe to the side plate, and that all fits nicely behind the distributor. The early side plate fitting is so close to the distributor that I think I might have to go late model side plate to run a hose to it.

Thanks!!!
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Old 02-26-2014, 12:19 AM
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I recommend using that gear pump for the antifreeze. It is the best factory pump available and will perform indefinitely with antifreeze especially if you put a strainer somewhere in the colder section of the loop. A little weep is no big deal. Make sure you use the lowest possible pressure cap for your header tank or exchanger - 4 lb is nice. On the early model is is easy to pull that crossover and tap the holes with 1/2" NPT. You don't have to remove the head; just suck out the filings with a shop vac.
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Old 02-26-2014, 12:02 PM
thatch thatch is online now
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SFL, Because the Johnson pump supplied with the Indigo FWC is designed as a "circulation" pump, I would strongly recommend that it is used on the coolant side of the system. It has no capability to self prime so getting the raw water to flow through it would certainly be a challenge. Making sure that the coolant side of the system has the ability to flow it's liquid easilly through the engine, manifold and heat exchanger is a must. Some of us, with electric/mechanical systems have even gone so far as to enlarge the side plate fittings from 3/8" to 1/2" fittings to insure better flow. In your case I would also recommend that you, at least, remove that plate and de-scale it to maximise flow potential. I feel that it is also very important to use a raw water strainer to insure that no debris finds it's way to the heat exchanger. As far as making the Thatch modification goes, I don't feel that the benefits will be as great as they would be compared to those on a strictly raw water cooled engine running at a steep angle. Hope I have been some help.
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Old 02-26-2014, 01:14 PM
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The Johnson pump could easily be mounted motor up on top of a thru hull where priming would never be an issue. The gear pump needs no additional flow relief to do its circulatory duties - it is in fact the strongest pump you'll ever see on an A4.
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Old 02-26-2014, 04:19 PM
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Hanley, The robust pumping capabilities of the gear pump are certainly better than even the flexible vane pumps like the Oberdorfers that we commonly use, however the same connot be said of the Johnson "circulation" pump. Using a Johnson pump as a raw water pump without aggressive filtration ahead of it is a prescription for disaster. The impellor in these pumps is a magnetically driven unit that will stop at the first sign of debris. A brief call to Tom Stevens at Indigo should head this project in the right direction.
Tom
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Old 02-26-2014, 07:09 PM
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Consider the Johnson CM30-7 pump functions much like a swizzle stick in your mai-tai. You can stir the drink and get a pretty good whirlpool going but as for bona fide pumping, not really. The impeller spins in free media, does not touch the pump body at any point. More accurately it stirs rather than pumps. Think about this as you consider the raw water pump must lift the water as high as the anti-siphon loop in the exhaust injection line.

I've made this comment before but if I don't repeat, it seems to fall through the cracks. 100% of the raw water you pump aboard must be expelled overboard. The vast majority of us do so with exhaust pressure/volume (p/v) via a waterlift muffler (muffler is a misnomer, same as freeze plugs). With an engine driven pump the faster the engine revs the more water is pumped aboard but you also have a proportionate exhaust p/v to expel it.

Not so with an electric raw water pump.

An electric pump operates @ full capacity at all times regardless of engine RPM and this is important - - EVEN AT IDLE when the exhaust p/v is at its least. Hanley will report he installed a raw water bleed-off modification to deal with it. He can describe it much better than I.

SFL -
We're more than happy to help but if you want to preserve your warranty you should really consult with Indigo regarding modifications outside their instructions.
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Last edited by ndutton; 02-26-2014 at 08:55 PM.
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Old 02-26-2014, 08:59 PM
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No question but that the mechanical pump delivers far more both pressure and volume than the electric. It is capable of intense circulation of whatever it handles. There are inherant weaknesses in any system utilizing an electric pump due to the great difference in capabilities. If you have a "mixed" pump pair one side is going to circulate far faster than the other. If you choose to move antifreeze with the mechanical pump you will gain greater flow and heat uniformity in the block. If you choose to pump raw water with the mechanical pump you will have greater cooling capacity at the exchanger but greater water to discharge. The issue comes down to where do you want that velocity and volume. If you pump antifreeze with the electric pump you need to do substantial modification to the block cooling circuit due to the relative weakness of the pump. If you use the electric pump for salt water the exchanger capacity may not be adequate for sustained high rpms, depending on the exchanger of course. The question of raw discharge diversion came about in an attempt to ease the burden of the engine in expelling water from the waterlock, not directly related to this issue. The electric pump in the raw water circuit imposes far less burden on the engine but still pumps more water into the waterlock than is required to cool the exhaust system. Actually I will now be discharging raw water three ways; the exhaust system, the new shaft log cooler, and a residual direct via a thru hull above the water line. The red hose is input from the exchanger and the "T" valve divides the flow between the exhaust system and the two lines serving the shaft log cooler and the overboard discharge.

Last edited by hanleyclifford; 07-13-2016 at 08:30 PM.
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Old 02-26-2014, 09:07 PM
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with all these issues, why not have a mechanical pump?
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Old 02-26-2014, 09:11 PM
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Quote:
Originally Posted by romantic comedy View Post
with all these issues, why not have a mechanical pump?
Having two mechanical pumps is always first prize but many boats, like the Catalina 30, don't have the flywheel option (readily). The other choice is the accessory drive bracket from Indigo but that carries some issues as well. There are no free lunches.
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Old 02-26-2014, 09:18 PM
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Quote:
Originally Posted by hanleyclifford View Post
If you pump antifreeze with the electric pump you need to do substantial modification to the block cooling circuit due to the relative weakness of the pump.
What Hanley deems substantial in my case was enlarging the sideplate input one pipe size and removing the thermostat. It was pretty easy.
Quote:
Originally Posted by hanleyclifford View Post
The electric pump in the raw water circuit imposes far less burden on the engine but still pumps more water into the waterlock than is required to cool the exhaust system.
Two cautions on this:

Caution 1: Hanley's electric raw water pump is an entirely different beast than the little Johnson pump provided in the Indigo kit. Be careful making decisions on your installation based on Hanley's version. If his installation is appealing to you, best to use the same type and capacity pump to realize the same result.

Caution 2: Most waterlift mufflers are pretty tolerant of elevated temperatures with reduced water flow (exactly what Hanley is manipulating) with one notable exception: the Vetus blow molded plastic muffler.

Regarding the questionable wisdom of electric FWC, I can speak for at least two of us without space at the flywheel and an aversion to the aux drive pump. The benefit of FWC trumps the liabilities of the electric pump. Life's a compromise.
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Last edited by ndutton; 02-26-2014 at 09:53 PM.
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Old 02-27-2014, 07:52 AM
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+1
Hanley uses a live-well pump. If you want electric raw water, I would do it this way.
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Old 02-27-2014, 09:58 PM
sail_flathead_lake sail_flathead_lake is offline
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Wow - thank you for all the detailed responses! This is truly a great group and resource for guys just getting into this (like me).

It sounds like I'll be using the gear pump for raw water, but should really bite the bullet and get a raw water strainer as those pumps are sensitive to sediment. The electric pump will require modifications to at least the side plate, which on my motor is cast, but I could easily modify or remake a new one like the new model motors (the one that came on my other motor is pretty beat up, so I'd be making a new one). The metal U shaped pipe connecting the head to the exhaust manifold may have too small an ID for the electric pump, and removing it would allow me to change to the Thatch modification, which everyone around here seems to like.

Question: The boat will be living 6 hours from my house, and it's likely I'll be paying the yard to winterize when it gets hauled occasionally (I might not always be present for the haul). THis was one of the reasons I wanted to go to FWC in the first place - I don't trust other people (even marine mechanics) working on my boat, and my last A4 shows that you can kill a motor with shoddy winterization. Given that the gear pump is not something you pull apart like an impeller pump to drain down, would I be just sucking pink antifreeze through it to winterize the pump and HX? Is there another option, especially a fool proof option if I'm not there to supervise?

Thanks!
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Old 02-27-2014, 10:04 PM
sail_flathead_lake sail_flathead_lake is offline
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Hanleyclifford,

Quote:
Originally Posted by hanleyclifford View Post
On the early model is is easy to pull that crossover and tap the holes with 1/2" NPT. You don't have to remove the head; just suck out the filings with a shop vac.
Are the holes in the head and the manifold already the right size for a 1/2" NPT tap, or would I need to tap drill them as well?

Thanks
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Old 02-27-2014, 10:06 PM
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Never use the pink stuff; always use automotive antifreeze. Trust a mechanic who knows this.
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Old 02-27-2014, 10:09 PM
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Quote:
Originally Posted by sail_flathead_lake View Post
Hanleyclifford,



Are the holes in the head and the manifold already the right size for a 1/2" NPT tap, or would I need to tap drill them as well?

Thanks
IIRC the holes will be fairly close; test with a 23/32" bit. If you are going to use the electric pump for antifreeze go "smooth" throughout. That means all plumbers style fittings (street is best where appropriate) and all 5/8" ID minimum on the hoses. Also best to lose the thermostat and go with a bypass loop which can be 1/2" ID hose.

Last edited by hanleyclifford; 02-27-2014 at 10:13 PM.
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Old 02-27-2014, 10:15 PM
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Please know that both the Thatch mod and sideplate hole enlargement for electric FWC are preferred based on speculation only. We think they're better, make sense to us and those with them report no problems.
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Old 02-27-2014, 10:17 PM
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Quote:
Originally Posted by ndutton View Post
Please know that both the Thatch mod and sideplate hole enlargement for electric FWC are preferred based on speculation only. We think they're better, make sense to us and those with them report no problems.
Nein, please upgrade that to tested and true.
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Old 02-27-2014, 10:32 PM
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SFL, even if my boat is 6 hours away, I'd make the trip to winterize..but that is just me. I certainly understand we all have individual circumstances, and if I could not get to the boat for winterizing, I'd recommend the same as Hanley.

Where we live in the mid-Atlantic, pink RV antifreeze is acceptable. We've had a couple times with temps down to 5 - 6°F this winter, and 15°F forecasted tonight which is quite cold for our area in late Feburary. Use the antifreeze recommended where you are..As Hanley noted, the green stuff gives better protection, and I think has a lower freeze point when mixed with water as opposed to full strength, unlike RV antifreeze.

In theory, with green antifreeze in the engine routed for FWC, yes, the only concern is the raw water cooled side of the circuit for winter (water pump & HX)

BTW - I think Moyer sells fittings that go on the top of the head & manifold for early model engines to replace that cast crossover fitting and allow hoses which could accommodate your own customized "Thatch mod".

Also, Neil is being conservative and rightly so, none of us want to state anything as gospel..However, some of us are experimenting, and I am sold on the side plate enlargement. I have my side plate at 1/2" NPT and have employed the Thatch mod on my late model engine, which I recently converted to FWC with the electric circulation pump. It works OK for me.
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Old 02-27-2014, 10:32 PM
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I am unaware of any real before and after testing with measured results, only general consensus. If it has been done and I missed it, apologies. Can you refer a thread??
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Old 02-27-2014, 11:06 PM
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Quote:
Originally Posted by ndutton View Post
I am unaware of any real before and after testing with measured results, only general consensus. If it has been done and I missed it, apologies. Can you refer a thread??
Hundreds of engine hours with the Thatch Modification and enhanced flow modifications with trouble free and steady cooling - that's my testing.
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Old 02-27-2014, 11:29 PM
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OK, I understand you're trouble free, so am I but that's not really measurable proof the Thatch mod is significantly superior to the factory original configuration. Like many here I believe it is but as far as I know, nobody has really measured the improvement and frankly, I don't know how to go about measuring it. Maybe IR non contact temp measurements of the manifold before and after the mod without any other changes??

That's all I was really trying to say. When we were working in the EI/resistor solution we actually measured the drop in coil temperature after installing a resistor. Development of the tensioner involved belt tension measurements to meet the Lycoming standard, stuff like that.
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Old 02-27-2014, 11:57 PM
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I think there are some things that do not lend themselves to quantitative testing, at least in the short run. The Thatch Modification just makes good theoretical sense especially for engines with any kind of angle - and it costs nothing. The value of coolant velocity is the same. Maybe we don't get to know such things except in observing the longevity and performance of our engines. Not scientific to be sure but I just cannot stop myself from trying new ideas.
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Old 02-28-2014, 07:55 AM
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The cooling mods are almost untestable with equipment you would have on hand. You would have to put temp and flow sensors inside the engine to really see what is going on.
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Old 02-28-2014, 11:28 PM
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Guys - thanks again for all the input. It turns out it may be a moot point to begin with. I just read in Tom's instructions that the FWC electric version isn't recommended for installations with a hot water heater in the loop, and we're planning on adding one of those next season, so it looks like I may have to get another mechanical pump shoe-horned in there somehow.
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Old 02-28-2014, 11:45 PM
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sounds like you made a decision.

What are the specifics as to why you cant put a pump on the fly wheel PTO or the accessory drive?
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