Electric FWC questions on early model motor

[sail_flathead_lake]

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:



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:



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!!!

[hanleyclifford]

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.

[thatch]

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.
Tom



























t

[hanleyclifford]

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.

[thatch]

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

[ndutton]

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.

[hanleyclifford]

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.

[romantic comedy]

with all these issues, why not have a mechanical pump?

[hanleyclifford]

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.

[ndutton]

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.

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.

[joe_db]

+1
Hanley uses a live-well pump. If you want electric raw water, I would do it this way.

[sail_flathead_lake]

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!

[sail_flathead_lake]

Hanleyclifford,

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

[hanleyclifford]

Never use the pink stuff; always use automotive antifreeze. Trust a mechanic who knows this.

[hanleyclifford]

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.