Merc 470 convert to open system ? Why Not

[customhd]

I just purchased my first boat and it is powered by a merc 170 (3.7L) 4" heat exchanger. Hold the bad mouthing please, I know about the problems.

I am considering converting to an open cooling system due to an internal leak in the heat exchanger. I will not be in salt water and I will winterize every year.

My only other "economical" option is to seal off both ends of the small tube with the hole in the very middle of it.

 

[Bondo]

Re: Merc 470 convert to open system ? Why Not

My only other "economical" option is to seal off both ends of the small tube with the hole in the very middle of it.

Ayuh,.... Welcome Aboard,....

Don will be along shortly,....
When he posts an answer for you,...
Read the Blue Text in his signature,....

I think it'll apply to your Plans......

 

[Don S]

Re: Merc 470 convert to open system ? Why Not

You can't just remove the heat exchanger and hook the hoses together and call it good. just won't work. Thermostat housings on raw water cooled engines are designed to always keep enough water going to the engine and enough going to the exhaust to keep things from burning up.
You also have an open deck design aluminum block with a cast iron head, and a cam seal not designed for any kind of water other than antifreeze. That is the camshaft that it rides on.
Take the heat exchanger to a radiator repair shop and see what they can do, or find another. But keep the engine a closed cooling system engine.

 

[customhd]

Re: Merc 470 convert to open system ? Why Not

I respect your guidance, but may I ask a few questions?

I am going to a GM style alternator, so no more inline VR and no Power steering.

I have attached an image of my connections.

Thermostat housings on raw water cooled engines are designed to always keep enough water going to the engine and enough going to the exhaust to keep things from burning up

I am having trouble seeing this problem? I think the Sea water would just take the place of the supply?

You also have an open deck design aluminum block with a cast iron head, and a cam seal not designed for any kind of water other than antifreeze. That is the camshaft that it rides on.

What is an "open Deck design"?
The manual states that there just needs to be a rust inhibitor added to the water if you don't use 50/50. I am still working on this bug?

Do you know of anyone that has actualy tried this?

Thanks for the help!

 

[Bondo]

Re: Merc 470 convert to open system ? Why Not

Do you know of anyone that has actualy tried this?

Ayuh,.... Not Sucessfully anyways,.

There's a guy a couple threads down that Thinks he's going to put a 470 in a Garden Tractor,....

Go up to the Adults Only thread,+ download the 470 manual,..
You might gain some insight from it...

 

[customhd]

Re: Merc 470 convert to open system ? Why Not

Bond-o,
All do respect, your comments have been of little help. I am on a tight budget and the boat was purchased for just a few bucks. I have valid questions and plenty of know how; so please offer some insight and not just jabs at me.

And shame on you for scoffing at a high school project that gets a kids hands dirty and might teach him something. Didn't you ever try to put an old lawn mower motor in a go-kart?

 

[Bondo]

Re: Merc 470 convert to open system ? Why Not

Didn't you ever try to put an old lawn mower motor in a go-kart?

Ayuh,... Sure Did,...
And,..
I learn early in life that using something Outside it's design parameters was usually a Bad Idea,....
That Don't Work...

Alpha drives can barely move enough water to properly cool that motor,...
As Designed...
Doing what you want to do Ain't gonna Work...

I Know what it's like being Short of Cash,...
But,.. Spending Good money chasing Bad ain't gonna make it any Better,...

If you wanta turn wrenches,... Keep going the way you're going...
If you wants go Boating,...
Fix that 1 Right,... Or Better Yet,... Sell it off,+ Buy something more Boater Friendly...

That's Life,....
I'm trying to save You,+ the high school teacher a Ton of Aggravation....
Polishing a turd, still leaves you with a turd.....

 

[TilliamWe]

Re: Merc 470 convert to open system ? Why Not

What is an "open Deck design"?
The manual states that there just needs to be a rust inhibitor added to the water if you don't use 50/50. I am still working on this bug?

"Open Deck" means that at the top of the block, the water jacket completely surrounds the cylinder. Meaning, it doesn't look anything like a small or big block Chevy. And it also means that the proper headbolt torque is CRUCIAL. And along that line, the proper cooling of the block and head is crucial. needs to be as even and constant as possible. And that is something that closed cooling provides, not open cooling.

How are you going to add rust inhibitor to a constantly flowing stream of raw water? The answer, you aren't.

Plain and simple, you need the closed cooling to make that motor work anywhere close to properly. Sorry it costs money for a new heat exchanger, but it'll cost a lot less to replace it now. But if you insist on monkeying around, then just remove that terrible engine, fabricate front motor mounts, install a 5.7 V8, and change the outdrive to a 1.50 ratio. You'll be dollars ahead of what you are trying to do.

Good luck.

 

[customhd]

Re: Merc 470 convert to open system ? Why Not

TilliamWe,
Thank you, this helps to get a better understanding of what is going on in there. I am a Design Engineer and it help to make a decision when you have facts and not just some blow hard that his mommy and daddy bought everything for him, instead of teaching him the value of a dollar.

I do not want to cause trouble but Bond-o has a very strange habit of poping off and giving little to no help in his replies. Just audit his posts (FYI not all aluminum is weldable)!

Don will be along shortly,....

This is the only piece of helpful advise that he has given.

I am new and find others here to be very helpful, for that I thank them!

AYUH! whatever the hell that means?

 

[Don S]

Re: Merc 470 convert to open system ? Why Not

I would suggest you stop complaining about the replies you receive, and accept them for why they were given.
Your idea might work with some trial and error, but you basically are ignoring all the information and trying to turn it into someone elses problem.
Your cooling system is not designed to work as a raw water cooled system. Never has been, never will be.
Try it if you want, but when it breaks, don't blame anyone here, just buy another and try again, keep it up till you get it right, then let everyone here know what it took to pull it off.
Once you really understand how a closed and a raw water cooled system really work you will understand all of the above replies.
It just isn't a matter of putting the available water thru the complete cooling system. It has to be done in the correct amounts to each part/section to make the complete system work.

 

[Bondo]

Re: Merc 470 convert to open system ? Why Not

Just audit his posts (FYI not all aluminum is weldable)!

Ayuh,... I guess ya got me there,... I haven't a Clue as to what you're talkng about...

Aluminum is extremely Weldable,...
I'm sure there's alloys of it that aren't,.. I just haven't run across 'em yet...
Although Magnesium does make for Interesting times sometimes..

AYUH! whatever the hell that means?

Google is your friend,... Use it...

 

[abj87]

Re: Merc 470 convert to open system ? Why Not

its your boat do what ever the hell you want... its just not going to work very well. the 470 is designed for a closed, pressurized cooling system, raw water is just not going to do the trick.

 

[Maclin]

Re: Merc 470 convert to open system ? Why Not

The underfunded budget factor, once all facts are laid out, would practically scream out to just fix the heat exchanger and any other related components.

The (dissimilar) metals used in the engine block and heads demand proper attention to corrosion inhibition and evenly applied heat dissipation to maintain the temperature constant. Raw water is on the fly and has varying entry temps, even if you designed some kind of drip or injection system to introduce a corrosion inhibiting agent (the cost of that could not possibly match just fixing the heat exchanger) there is not enough time for it to "fix" the RAW (good term) water coming into the engine's cooling passages and components. Plus, your system already has a way to use the raw water coming in as is for heat dissipation yet not allow it to harm the inside of your engine but still enjoy consistent heat dissipation and temperature constant. It is called a heat exchanger.

Just fix what is there my man, you will be way ahead at budget crunch time.

 

[chiefalen]

Re: Merc 470 convert to open system ? Why Not

Another happy owner of a 170, 470, 3.7 whatever you want to call it motor.

He ran into one of the problems with the design flaws and is floating down de-nial.

That motor should go on a one way trip, before you spend any money on it, sorry the truth hurts, but it's still the truth.

 

[mylesm260]

Re: Merc 470 convert to open system ? Why Not

I'm going to go against the flow of the crowd here.


I installed an automotive 4.3 onto an alpha.

I used automotive coolant hoses, and Plastic T's and fittings from home depot.

Alpha water pump ----> T -----> Water pump intake on block
Alpha water pump ----> T -----> Bottom of manifolds

Upper thermostat ---->T----> Tops Both Risers


I ran this setup for years before I switched to a closed system with absolutly no porblems. The automotive thermostat heated the engine perfectly to 190.

You will find a lot of resistance in this forum to thinking outside the box.

Unless someone can offer some reason as to why that shoudn't work for you aswell, I would say go for it.

The talk of water flow doesn't make any sense to me, as the same amount of water would be needed to cool the exchanger as is needed to cool the engine.

The non closes system "Stores" water in the manifolds for the engine to circulate with I honestly cannot think of any reason why it woudn't work. Someone tell me I'm wrong....

They are all right in saying the proper thing to do is replace the exchanger. But if your on a tight budget, I say go for it...

Just remember, salt water is the enemy, and flush your motor every time you take it out.

 

[Bondo]

Re: Merc 470 convert to open system ? Why Not

I'm going to go against the flow of the crowd here.

Ayuh,...

And you Obviously have No Idea what a Merc 470 is Either....

 

[mylesm260]

Re: Merc 470 convert to open system ? Why Not

An archaic Frankensteined together 3.7L 4 banger that shares the same pushrod head as some old big block?


Are you saying a 3.7 liter has more cooling needs than my 4.3? Is there some aspect of the 3.7 that REQUIRES a closed cooling system?

Are you saying a closed cooling system is some way more thermally efficient than running the water directly through the engine?

I'm not saying I'm right, I just want to know why I'm wrong =)

 

[rodbolt]

Re: Merc 470 convert to open system ? Why Not

mylesm260
no what they are trying to tell you is your clueless to the design of the block and head assy of the 470.
even the merc factory engineers simply could not make it work so it was only in production about 5 years.
the motor was a very nice design that simply failed miserably.
looked good on paper, failed the real world test admirably.
open deck and high ouput doesnt work well at all.
I am glad your V configuration worked well.
sometimes,even with a 470, one gets lucky.
however the 470 merc motor never worked well and reliably and was dropped due to this small fact.
now to satisy the angeneer aspect.
ok aluminimum block, open deck, cast iron head
tells me instantly there will be an expansion rate differential.
now with closed cooling we can almost make both ends of the block and the head heat at about the same rate.
even though we will still have a thermal expansion ratio that will vary wildly.
now we go to raw water cooling, block is about 3ft long, hot water has to exit someplace and cool seawater come in.
now is where the issue starts.
now one end is still hot and the other has cold water.
the cast AL cools rapidly and shrinks, the cast iron much slower.
in fact even with closed cooling the early versions with a cast exhaust manifold and 3" exchanger fought this issue.
if you caught it early and carefully removed the head and inspected the gasket you could actually see the shiny spots where the cyl liners were moving and polished the gasket surfaces.
but like I say, it was an abortion that even merc could not fix so they dropped it.

 

[JustJason]

Re: Merc 470 convert to open system ? Why Not

I'll add to what Rodbolt says....
Especially with the open deck design. What you really have are 3 different Metals. The iron of the head, the aluminum of the block, and the steel of the head gasket.
On an open deck motor there is water on the underside of the head gasket. If there is enough iron content in the gasket its going to rust on the inside. If you run it in salt that way even once the head gasket is going to start rotting from the inside out.

 

[mylesm260]

Re: Merc 470 convert to open system ? Why Not

I totally understand your point.

I've worked with Japanese Domestic market Nissan engines. Two of the most popular engines are the SR20DET and the CA18DET.

One is a 1.8 Liter cast iron block aluminum head closed deck.
The other is a 2.0 liter cast iron block aluminum head open deck.

While the 2.0 liter has slightly more displacement, the 1.8 has a higher horsepower "ceiling"

The 2.0 open deck motor blows head gaskets at about 350-400 HP, where as the 1.8 liter closed deck motor holds out until around 500.....


Having said all that, I still think you guys are giving the corrosion resistance of antifreeze vs fresh water too much credit...

If if was in a fresh water lake, I think he would be okay... He would shorten the life of his engine, yes, but it sounds like it's a bit of a garbage-barge anyway...

Also remember, that even in a "closed deck" block, there are STILL water passages going through the opening of the block, through the head gasket and into the head..... less surface area in total, yes, but still the same "thickness" of head gasket to corrode through before it leaks...