5.7 Mercruiser convertion to CCS, stainless risers also?

[GaryDoug]

I recently purchased a 1999 Mariah Z202 bowrider with the 5.7 Mercruiser TBI. The boat had been used in Idaho since new up until about 1 year ago, The engine looks almost like new. Then it was used in St Augustine, FL. I am in the Tampa Bay area (Gulf Coast). The boat is now on a lift ready for use anytime in the gulf. I have pretty much talked myself in to adding a closed cooling system. But I believe that still leaves the engine vulnerable to water ingestion due to corrosion of the exhaust manifold risers. If I'm not mistaken, my options are to either replace the risers every 2-3 years or maybe switch to stainless steel risers. Does anyone have recommendations? I would prefer to use the stainless approach if that is practical and would last for 5 years or more. I am not independently wealthy, so go easy on the investment suggestions ;-) Thanks

 

[Bondo]

Does anyone have recommendations?

Ayuh,... Forget about the closed coolin',...
It's an old motor, 'n been in the brine for a year,....
The coolin' passages already have salt in 'em, 'n I hear it'll interact with the antifreeze causin' Major problems,...

 

[alldodge]

Have to agree I wouldn't do it.
Now tpenfield did it with his motors after some hours and are still doing OK, but it is rolling the dice. If your willing to flush the block, then add closed cooling, and maybe for the next couple years, drain, flush and refill.

Standard OEM would be my first choice, next would be Barr then if you go closed cooling, go with EMI with SS risers. Your not going to gain anything to speak of with going to high performance exhaust with a standard engine.

 

[tpenfield]

As AD mentioned, I added closed cooling to my twin Mercruisers with 740 hours . . . BUT . . . they were 100% fresh water. A year of salt water would probably put you into the heavier scaling category and not a good candidate.

Also, I learned after the fact that a good cooling system acid flush is helpful to remove the internal rust powder that even a fresh water engine will accumulate.

Also, I have stainless steel risers/elbows that came with the boat as OEM equipped, and the closed cooling system is a FULL system, so it cools the block and the manifolds. I had the PO put new manifolds on the engines as part of the sale, because the stainless steel elbows depleted the manifolds during its fresh water years.

Not sure you can do much about the prior salt exposure, since the iron tends to hold onto it once it 'sees' it. Maybe an oxalic acid flush followed by a neutralizing flush will help.

 

[GaryDoug]

The coolin' passages already have salt in 'em, 'n I hear it'll interact with the antifreeze causin' Major problems,...

I am interested in any reference you have to that problem. Can you provide a link to a report or an article somewhere? The guys who sell the kits say that's possible but if you flush the system according to their recommendations, it shouldn't be a problem. Of course they have something to gain by saying that, don't they?

The prior owner said the boat was used about 50% in salt water for a year, which corresponds to about 50 hours in his case. The rest of the time was usually spent on the St. Johns river nearby.

 

[Bondo]

Can you provide a link to a report or an article somewhere?

I can't, just have read it many times over the years,....

The antifreeze side of the H/E ain't easy to clean, 'n once clogged it's pretty much junk,...

Goin' to closed coolin' is usually done with a brand new motor, or a reman that the block, 'n heads were boiled, 'n cleaned to bare cast iron,...

 

[GaryDoug]

Interesting. The places that sell the kits say "no problems", but the places that don't sell the kits say "many problems".

 

[tpenfield]

You could try it but you probably want to do a soak & flush of the cooling system . . . first with Salt-away and then with oxalic acid, and then finally a neutralizing flush with Arm & Hammer or Borax, then plain water.

That would be about the best you could do. If you had the engine out of the boat, you could also pop out the core plugs and clean out any sediment that is in the lower portion of the cooling passages.

 

[Scott Danforth]

I currently boat in the Tampa/Bradenton/Sarasota area and I used to design heat exchangers for marine motors (tier 1 supplier to Mercruiser, Volvo Penta, Indmar, Ilmor, Seven Marine, Mercury Racing, Caterpillar, Cummins, etc). so while I may not be an expert, I may know a thing or two about heat exchangers

If your boat spent a year in St Augustine, the insides of the block and heads will have scale. that scale does a few things, first, it prevents a proper transfer of heat from the block to the coolant. second, it comes loose and plugs the heat exchangers, . the gap between the tubes is about 0.020" so anything bigger than the point of a pin gets stuck in the tube bundle. to unclog a heat exchanger inside the tube bundle is to remove and replace the heat exchanger. the tube bundle is an excellent filter

the boat is 15 years old, the sediment in the block has to be removed, PERIOD. most fresh water boats have a few inches of sediment in the block that can only be removed when you pull the motor. this sediment which includes rocks, sand, small fish, and some shells will also plug the heat exchanger. it has to be removed.

you can put a heat exchanger on your fresh water motor if you pull the motor, pull the heads and clean out the sediment from the block

you can also put a heat exchanger on the motor that has been in salt, however you have to do the following:

pull the motor, pull the block apart, send it to a machine shop, have them bake the block and heads to remove the scale, put it thru the bead blaster and shaker to remove sediment, etc, then rebuild the motor

OR

rig the motor up to run on a loop of coolant, fill the block and heads with oxalic acid. let sit for a few days. rinse, then repeat. this will remove the rust and scale

pull the heads, have the motor on the engine stand upside down and flush out the 15 years of sediment in the block

OR

drop in a new rebuilt motor

However if I was you, I would simply go boating, enjoy the boat, and start saving up for a set of manifolds and risers. in 3 years, replace them. then every 5 years after that

regarding the risers with closed cooling, they are a maintenance item that gets replaced on the same schedule regardless of type of cooling system. even the performance stainless exhaust will rust out after a while. the stainless costs twice as much, however lasts twice as long

 

[GaryDoug]

If your boat spent a year in St Augustine, the insides of the block and heads will have scale. that scale does a few things, first, it prevents a proper transfer of heat from the block to the coolant. second, it comes loose and plugs the heat exchangers, . the gap between the tubes is about 0.020" so anything bigger than the point of a pin gets stuck in the tube bundle. to unclog a heat exchanger inside the tube bundle is to remove and replace the heat exchanger. the tube bundle is an excellent filter

Excellent points. But to prevent plugging the exchanger, why not install two of these with a ball valve to switch over ?
https://www.amazon.com/Champion-Cool...KYG2YGNH28PE2E
or
http://www.tefba.com/index.html

 

[Bondo]

Ayuh,... It sounds like yer gonna do it, regardless what's said here,...

Go for it, 'n come back in a year or 2, 'n tell Us how it works out for ya,...

 

[GaryDoug]

Ayuh,... It sounds like yer gonna do it, regardless what's said here,...

Go for it, 'n come back in a year or 2, 'n tell Us how it works out for ya,...

Actually I am leaning towards not doing it. But not because of your unsubstantiated remarks. I respect folks who offer some kind of proof of what they say, not just hearsay.

 

[Bondo]

Duly noted,...

 

[tpenfield]

The downside, even with the preventative flushing, would be in a couple 2-3 years of use, you will have lost cooling capabilities in your H.E. to the point where you need to replace it.

You will have to decide what is best, but I think all of the posters here have pointed out the potential issues, given that the engine is older and has seen some salt water.

For myself, having taken apart an engine that was run in salt water on my previous boat, I was blown away by how bad the internals of the cooling system looked. That is why I went with closed cooling on my current boat, given that it had never seen salt, yet was 16 years old (740 hours) at the time I bought it, and was going to run/keep it in salt water.

 

[Scott Danforth]

Excellent points. But to prevent plugging the exchanger, why not install two of these with a ball valve to switch over ?
https://www.amazon.com/Champion-Cool...KYG2YGNH28PE2E
or
http://www.tefba.com/index.html

you obviously dont understand the installation of a heat exchanger and what get plugged. the mesh on that filter is no where near fine enough. think 30 micron

you also do not understand the existing restriction in your system and the additional restriction of adding such filters would impose

anything over 3" of water restriction and the flow starts to drop off significantly

 

[GaryDoug]

I don't understand? YOU said the spacing is .020" which is about 508 microns. You: "... the gap between the tubes is about 0.020"
Where is this 30 microns (about .001") coming from? You can put 20 of those into the .020 gap that YOU specified. Are you confusing microns with mils?

I understand hydrodynamics. The length of the flow has little to do with the pressure loss. The length of the restriction is about .010" for the standard filters, a little more or less with the optional screens.

 

[Scott Danforth]

50 microns is the diameter of a human hair, or 0.0020"
40 microns is 0.0015"
30 microns is about 0.012
25 microns is 0.010"
8 microns is 0.0003
2 microns is 0.00008

the filter you showed is a 1000 micron at best, maybe 2000 as the gap appears about 3x larger than the 0.018 wire used for the mesh

 

[GaryDoug]

I suggest you "learn up" on your measurements. 30 microns is NOT 0.012 inch. 30 microns is 0.0012 inch. You are off by an order of magnitude.

An ordinary kitchen sieve is about .040" (1000 microns). I am sure the filters referenced are way finer. One even states that the filter includes 3 different screens one coarser and one finer than the standard one.

 

[Lou C]

Interesting; having just taken the heads off a salt water cooled engine (in salt 15+ years) I can tell you that as Ted noted the cooling passages were full of flaking corrosion. Obviously the OPs boat will not be this bad but the issue is no one can tell you how much corrosion is inside because you're not pulling it all apart . One thing you can do to get an idea is drain the block and disconnect the lower end of the big hose from the Thermo housing to the front water pump and let that drain. Then remove the thermo housing from the intake manifold. Let it dry out . What you see in the intake, is likely what the rest of the engine looks like inside. If you see flaking corrosion then you'd have to do what was suggested above to clean it out; but if it's just light surface corrosion you might be able to make it work.

Keep in mind as long as you are meticulous about maintaining the exhaust sys (ie replace the whole works every 5 seasons) you will likely get at least 10 years out of that engine in salt.
The things that shorten the life of marine engines are overheating over propping and not maintaining exhaust.

 

[GaryDoug]

Thank you Lou for a very helpful suggestion and I appreciate that. I will do exactly what you suggested.

As coincidence would have it, I just today tracked down the guy who originally owned the boat before the 2nd owner from whom I bought it. He did move from Idaho to Jacksonville, FL in 2014, but lived on the St. Johns river about 50 miles upstream and he said he never went into the Atlantic or anywhere near it. I guess I got wrong information from the guy from whom I bought it. So the only salt water use was in my local Tampa Bay waters for a few months at worst in 2016. And half of that was in fresh water lakes.