Installing closed cooling system..... Should I Descale the engine

[josh1981]

I have a 95' mercruiser 5.0, 305. I just recieved a new San Juan cooling system for my boat. I know it is late in the boats life to install a freshwater cooling kit but it was a gift, so I am excited to install it. My question is should I do some type of descaling before I install it? I have read using a muriatic acid/water mix to clean the inside. Has any one done this. Is it worth doing and if so how do I do it? Thanks

 

[bruceb58]

Re: Installing closed cooling system..... Should I Descale the engine

If you call up San Juan, they will tell you not to bother installing it if its ever been in salt water.

 

[telstar1]

Re: Installing closed cooling system..... Should I Descale the engine

please do see what san juan say about that.I recently did exactly what you are doing, 2002 5.0 m/c, they told me it shouldnt be a problem. They were right it works great.I did remove my manifolds and beat the heck out of them, got some scale out, and changed the coolant(water) several times in first few hours...it was pretty gross looking the first time....after several flushes it is now normal looking.
I was very concerned and skeptical about the whole thing but San Juan's advice seemed right on.

 

[zbnutcase]

Re: Installing closed cooling system..... Should I Descale the engine

I have installed many, many kits on used high hour engines and have never had a problem. Not one,ever.

 

[josh1981]

Re: Installing closed cooling system..... Should I Descale the engine

I understand not to bother after its been in salt water. The kit was a gift so what do I have to lose? The boat was all fresh water up until the last 20 hrs or so of use. I had the manifolds and risers off last season and banged some of the crap out, not much there but some.

 

[josh1981]

Re: Installing closed cooling system..... Should I Descale the engine

I have installed many, many kits on used high hour engines and have never had a problem. Not one,ever.

My engine has just under 400 hrs on it, not that it makes much of a differance. So did you just install the kit and change the coolant often and not bother with "descaling/cleaning"?

 

[Speakrdude]

Re: Installing closed cooling system..... Should I Descale the engine

When I install on older salt water engines, I use Prestone flush / water after the conversion is made. Run for about an hour, empty, fill with clean water, run for another hour, empty. Fill with 50/50 antifreeze, done.

 

[bruceb58]

Re: Installing closed cooling system..... Should I Descale the engine

please do see what san juan say about that.I recently did exactly what you are doing, 2002 5.0 m/c, they told me it shouldnt be a problem.

Interesting! I had 60 hours on my engine when I called them. They said NOT to do it.

To the OP, you have an Alpha or a Bravo? If I was going to install one on an Alpha, I would probably switch to an engine mounted raw water pump. Other than worrying about your heat exchanger clogging up and overheating your engine, you have nothing to worry about.

 

[MCL]

Re: Installing closed cooling system..... Should I Descale the engine

I was about to do this on my 4.3 merc until I found out I have a cracked block and installed FWC with the new engine.

I was planning then to thoroughly flush the engine,use some acid to descale and install some easily cleanable filter to catch the crap before it reaches the heat exchanger.And then of course replace the coolant often at the beginning.

 

[HT32BSX115]

Re: Installing closed cooling system..... Should I Descale the engine

Interesting! I had 60 hours on my engine when I called them. They said NOT to do it.

To the OP, you have an Alpha or a Bravo? If I was going to install one on an Alpha, I would probably switch to an engine mounted raw water pump. Other than worrying about your heat exchanger clogging up and overheating your engine, you have nothing to worry about.

It sounds like it depends on who you call up there.

I bought mine from THESE GUYS in 2006. It was shipped directly to me from San Juan "up the road" in Bellingham.

I told them that I had a 10+ year old (1997 454) with 122hrs of "fresh" (raw) water use since new. I called them to discuss some finer points of installation and asked about the age and hrs of my engine as an "aside".

They told me I should thoroughly flush the engine and manifolds but I would be fine.

I had the engine out and on a stand so I removed ALL the core plugs and REALLY flushed the water jacket. It's amazing how much sand and rust flakes I got out of it. I got a fair amount of rust out of the manifolds too.

I filled the entire system with 50:50 DEXCOOL. I'll probably flush it this summer.

It's worked flawlessly ever since. I wouldn't own an I/O without closed cooling!


ymmv


Rick

 

[bruceb58]

Re: Installing closed cooling system..... Should I Descale the engine

I told them that I had a 10+ year old (1997 454) with 122hrs of "fresh" (raw) water use since new.

That is the difference. Mine was 60 hours of salt water usage. If mine was fresh water only, I am sure the answer would have been different.

Be interesting to see what DonS has to say here. He has some opinions on putting on a system on a previous salt water motor.

 

[HT32BSX115]

Re: Installing closed cooling system..... Should I Descale the engine

I think most here have said, 100hrs and/or something like 1 year.......I know it was 100hrs + xxxx.

I may be "over the top"......I'll find out if I have to flush out the heat exchanger someday using a rust dissolving solution.....

 

[josh1981]

Re: Installing closed cooling system..... Should I Descale the engine

Since I have the kit I am going to install it. I think I will do some type of acid wash to clean out the motor and manifolds the best I can and then change the coolant often for the first season.

 

[HT32BSX115]

Re: Installing closed cooling system..... Should I Descale the engine

Since I have the kit I am going to install it. I think I will do some type of acid wash to clean out the motor and manifolds the best I can and then change the coolant often for the first season.

Josh,

There is a FOMOCO product that was used to flush out the V-6 engines that they put in the Taurus some years ago.

There evidently was an electrolysis problem so bad that it literally corroded the water pump impeller completely away. When I pulled the pump off my Mom's 98 Taurus a few months ago, The steel impeller looked like a SAW BLADE!!


The product was recommended by Ford in a service bulletin to remove the rust and scale from the engine, radiator and heater cores after replacing the pump and initially flushing the sytem.

I don't know what it consisted of but I'm sure you can get it from any Ford parts supplier....The FOMOCO part number is F8AZ-19A503-AA


Cheers,



Rick

 

[Brucetafer]

Re: Installing closed cooling system..... Should I Descale the engine

when i worked at a diesel shop, they had a hot water flush that used acetone and acid wash, it was nasty stuff, but it cleaned out the cooling perfectly... made a 500K mile engine looke brand new...

 

[dan t.]

Re: Installing closed cooling system..... Should I Descale the engine

I changed a 305 Merc from a block only to a full system, boiled out the manifolds with muriatic acid, I had no problems at all.I think the only time you would have a problem is with a badly rusted raw water system that was run in salt water