adding freshwater cooling to stern drive: doable? and what advantages?

[driscollies]

I have a mercruiser stern drive and I'd like to add a freshwater cooling system. Is this doable by an average DIYer? I would guess I'm mechanically decent/average. Do all my maintenance now, comfortable with cars, have rebuilt a few outboard engines, etc. But I also don't understand electrical systems very well and I'm pretty lost when it comes to gears/shifting assemblies and I don't know that I'd feel comfortable hauling out a big sterndrive engine and rebuilding that whole thing. Average mechanic.

I found a freshwater cooling kit online. Is this something that takes alot of know-how to install? Would I have to remove the engine? Or is it more a matter of just hooking up the fresh water to the intakes somehow? What's involved?


Second general question, what advantages will this give me? Will it allow me to run in salt water without worrying as much about engine corrosion, like in the exhaust manifolds and whatnot? Is there any way to run antifreeze through here, so I don't have to drain the block whenever I boat over the winter?

EDIT: I should also probably say, i've never ran this boat in salt water. Just fresh, but I'd like to be able to dabble in salt if I can!

thanks in advance for any and all input

 

[bruceb58]

How old is your block? Problem with putting it on older blocks is there is so much corrosion, that it may block up your heat exchanger. Since you have only been in fresh, you may get away with it.

Most after market systems are half systems and don't cool the manifolds. If you have a Merc Alpha, good luck getting enough water flow from the in drive water pump for a full system which also cools manifolds.

What drive and engine do you have?

 

[tpenfield]

I put an SJE 'closed cooling' (aka fresh water cooling) system on my twin Merc 7.4's. It was wicked fun Not very hard . . . tedious though. Took a few days overall.

here is the link to my thread on the installation . . .

http://forums.iboats.com/forum/engin...-arrived-today

If I were to do it over, I would probably flush the engines with oxalic acid (wood bleach) before adding the closed cooling. The engines had 740 hours of lake Winnipesaukee prior to my adding the closed cooling. the boat is now used/kept in salt water.

 

[driscollies]

thanks for all the info.

I have a mercruiser, don't remember all the specs exactly but I will get them.

Are these the kind of things one can buy used, or does it pretty much have to be new?

Do they avoid all the corrosion issues that come with running in salt?

thanks

 

[HT32BSX115]

Are these the kind of things one can buy used, or does it pretty much have to be new?

Do they avoid all the corrosion issues that come with running in salt?

thanks

Howdy,

About 11 years ago, I installed a San Juan Engr system on my 1997 Mercruiser 454. It had 122 hrs of non-salt water operation.

It works flawlessly, and I love it. It is a "full" closed system, cooling block, heads and exhaust manifolds.

Many systems only do the block and heads, so you still have salt water corrosion of the manifolds and risers. ALL closed systems however will have salt water exiting out through the risers.

I wouldn't have an inboard or I/O boat without closed cooling.

Cheers,

Rick

 

[tpenfield]

I would not buy a used closed cooling system (heat exchanger, etc), if that is what you are asking. I would also go with a 'full' system, rather than a 'half' system, as Rick mentioned.

In salt water, you will need to have the heat exchanger cleaned out every few years, as salt scale will build up inside of the water passages on the 'open' side of the system. The closed cooling systems avoid running salt water through the engine block, cylinder heads, and exhaust manifolds (assuming full system). You will still have salt water maintenance concerns with the exhaust elbows (risers) and the entire outdrive and transom assembly.

 

[driscollies]

thank you for the replies.

where is the best place to buy a closed cooling system? I googled and they all seem so expensive! (which is why I was asking about used. Used seems to be about half the price of new or even less)

also, full system seems like the way to go if half system leaves things open to corrosion. So I'm i'm understanding properly, a full system protects head, block, and manifold, but the risers and outdrive are still exposed to corrosion. With a half system, the head and block are protected, but the manifold, risers, and outdrive are still exposed.

so i assume I still need to flush after use, even with the full system?

one other question: Is this even worth doing, since the motor has been well used in freshwater? It's not "too late" for me, is it?

thanks!

 

[bruceb58]

Call up San Juan Engineering and talk to one of their techs. I was going to install a half system on my engine with 75 salt hours and they talked me out of it.

If you have an Alpha drive(water pump in the drive) I doubt you could even do a full system without changing to an engine driven pump and pulling water through a thru hull fitting.

 

[HT32BSX115]

thank you for the replies.

where is the best place to buy a closed cooling system? I googled and they all seem so expensive! (which is why I was asking about used. Used seems to be about half the price of new or even less)

///////////

one other question: Is this even worth doing, since the motor has been well used in freshwater? It's not "too late" for me, is it?

thanks!

It's probably also worth mentioning that with closed cooling, the engine will run MUCH better because you'll run hotter and the engine will have a much more even controlled temp. I think mine has a 180 degree stat (Ted?) Maybe it's a 160 but the gage hangs around 180. It's always better to run these engines hotter.

My engine was used in fresh water for about 10 years before I got it. If the manifolds are rusty, I would replace them before installing the system. Also, I would probably do a hot flush using Cummins Restore Plus, Motorcraft VC-9 cooling system "cleaners" or other cooling system rust removal product

. They specifically remove rust in teh block, heads and other cast iron components. You don't want rust flaking off and clogging your heat exchanger.

You didn't say what engine and drive you have.....and how long it's been used. That's a factor because you have to weigh the cost of the closed cooling system vs the cost of rebuilding the engine. It may not be worth installing a closed cooling system until you rebuild/replace the engine and/or manifolds.

In Salt water, one should probably replace the manifolds and/or risers every 4-6 years or so. (they slowly clog to the point of restricting cooling water flow and can cause overheats.

Manifolds used in "fresh" water can last 20 years (or more) but will still have rust flaking off internally(enough to possibly clog up your new heat exchanger)
. In an open system, that rust just exits out the risers along with the cooling water.

In the block, the rust usually doesn't make it out and just settles to teh bottom of the water jacket. (when you drain for winter, poking a wire, thin rod or screwdriver etc will usually break that stuff loose, but there's still a LOT in teh block that could clog a heat exchanger.

When I installed my San Juan Engr system, I had the engine out of the boat and on an engine stand. I removed all the core-plugs (AKA "freeze" plugs)rotated the block upside-down and thoroughly flushed the block water jacket multiple times. I got a LOT of loose rust and other debris out of that block! Had I NOT done that, I suspect it would have clogged the heat exchanger long ago.

You can find those systems all over the net........aside from the actual heat exchanger, installation is just a plumbing exercise.

 

[tpenfield]

HT32BSX115 160 F thermostat on the Merc 7.4's. So they will run in the 165-175 F range. the older 7.4's had 143 F thermostats.


driscollies
If you have an older engine that has been run in fresh water only for its life, it is certainly possible to add closed cooling . . . BUT . . . do a good flushing of the engine block/manifolds, etc before adding it. Many of the radiator flush products will get rid of the rust powder that is captive in the engine block, etc., and you'll be starting off with a pretty clean engine.

I paid about $1,000 (each) for the closed cooling system on my Mercruiser 7.4's. smaller engines will be less money. the concern about buying a used system is 'why is it no longer being used?' typically would mean to me something was wrong with it and it got replaced. . . . you could end up with problems and have to replace it anyway. Might as well start off with a new system. (Yes, boating is expensive)

You can certainly flush the open side after each salt water use, if you want, assuming you trailer launch each time you use the boat. I have always kept my boats in the (salt) water for the season, and everything still seems to be there when I take the boat out. Anodes are your best protection for the outdrive and heat exchanger to ward off corrosion.

 

[driscollies]

Huh, well, I have an Alpha, so does that mean it's not even worth it, or that I need to stick with a half system?

also, I don't know how long it's been used. I got it used and have put about 15 freshwater hours on it. I don't have it right in front of me but I want to say it has 150ish hours on it? 200?

Still worth it?

thanks!!


EDIT: Or, what are your thoughts on just flushing it after use? I trailer it, so I can flush it with that salt-away stuff every time....

 

[tpenfield]

If you are going from purely fresh water to salt water, then IMO it is worth it. I will never run an I/O in salt water without Closed Cooling after seeing the insides of the engine on my old boat. Kind of a miracle they last as long as they do in salt . . . but when they are done, nothing can save them.

 

[driscollies]

Thanks for all the replies.

As I've bees reading old posts, I've mostly seen warnings about how even in freshwater all the rust and scale makes it not a good idea to put closed cooling on a used motor, even freshwater.

Is this still true even with the flushes that were mentioned? I'd hate to drop a grand on a cooling system and then have it not do anything, or clog things up so I overheat. Or, is there a way to inspect my engine beforehand, to see if it's even a good candidate for a closed cooling system? See how much scale is in there? What part should I be checking?

Thank you all

 

[tpenfield]

It is a judgement call that you will have to make. The flushing of the engine block should help. If you are going to run the engine in salt water, then I would recommend putting the closed cooling system on it.

I looked inside the thermostat housing and the openings where the recirculating pump attaches on my engine. There was no rust scale, only the powdery surface rust. The exhaust manifolds were also brand new. So, in my judgement, it was an acceptable candidate for closed cooling, considering what would happen to it in the salt water.

 

[Scott Danforth]

even if your block is pristine, you still need to flush because sand, chunks of small critters, etc are sitting in your motor cooling passage ways.

I added a heat exchanger to my motor when I moved to florida from the great lakes. I spent an entire day flushing the motor before hand, and I had the motor apart a few months prior. I still got about 2# of sand out of the block from the few trips I used the boat on lake michigan prior to moving down here.

 

[driscollies]

Judgement call, huh? well, shoot. I trust myself least of all!

thanks for all the great info. Maybe I can add one more piece to the puzzle... as I've been reading, it's been mentioned in quite a few articles that bays are a place in which you may not need freshwater cooling if you flush your engine every time. I don't actually plan on going in the ocean, I will be exclusively in the san francisco bay, which is apparently way less salty than the ocean.

Considering that my engine is old (just checked to confirm the hours, and I was way off?almost 400 hours), and I'll really only be in the bay.... and I'll be trailering it, so I can flush it after every use.....

Does that change the equation at all? I'm almost leaning more towards just not bothering with a freshwater system?

thanks!

 

[tpenfield]

Judgement call, huh? well, shoot. I trust myself least of all!

thanks for all the great info. Maybe I can add one more piece to the puzzle... as I've been reading, it's been mentioned in quite a few articles that bays are a place in which you may not need freshwater cooling if you flush your engine every time. I don't actually plan on going in the ocean, I will be exclusively in the san francisco bay, which is apparently way less salty than the ocean.

Considering that my engine is old (just checked to confirm the hours, and I was way off—almost 400 hours), and I'll really only be in the bay.... and I'll be trailering it, so I can flush it after every use.....

Does that change the equation at all? I'm almost leaning more towards just not bothering with a freshwater system?

thanks!

No. Still your call.

 

[bruceb58]

You also have an Alpha which means you are pretty much stuck with a half system anyway. Still way better than none but something to think about. Did you ever call San Juan Engineering? They talked me out of it on a salt water boat with 70 hours on it.

 

[driscollies]

thanks for all the info. I will call san jaun engineering tomorrow.

From what I'm gathering, these kits are mostly heat exchanger and tubes, with specialized risers and such. How difficult is it to convert from one mercruiser cooling system to a different mercruiser cooling system? There is someone near me who is selling a closed cooling system for $50 because they're parting out their boat, but they say theirs is for an "inline six" mercruiser with a pre-alpha outdrive. I have a BBC. Is it worth spending to 50 bucks essentially to get the heat exchanger, and then planning on spending more on the risers and stuff?

I figure there's a chance that most of the stuff here is universal?I wouldn't be shocked if the risers were the same, and if the heat exchanger was the same, and then things like the hoses should be fairly universal, right? And hey, the risers may even be the same if we both have GM engines.

Or am I way off base? are these things really, really, model specific, to the point that something made for one GM motor just won't come close to being able to work on a different GM motor? I'm seeing old posts where people are saying that "mercruiser X cooling system has parts that work for Mercruiser Y motor", just wondering if these are a swap? Or if I should just keep looking?

Like, I wonder if the cost of closed cooling is the heat exchanger, and once you have that, the rest of the parts are kinda universal.

thanks for any insights!

 

[tpenfield]

Here is what my SJE "MC-324" kit looked like . . .



It is pretty much the heat exchanger, hoses, and fittings. The 'risers' are part of the engine, not the cooling kit.

The key difference between the systems for different model engines is in the capacity of the heat exchanger.