Just put on new AFR enforcers after suffering reversion problems with hp500's and stainless marine exhaust, previously had Grumpy Jenkins iron heads. We're welding extensions to the inner riser jacket to make them dry to nearly the tip of the tails, which will hopefully resolve the reversion issues. Just picked up heat exchangers from Sick Stinger to convert to closed cooling to preserve these new heads & intakes. They come with engine brackets but I hate the look of them on the front of the motors so am thinking to put them on the stringers outside of the engines (where saddle tanks often go). Had a couple questions:

1- Best method of flushing out these blocks to avoid issues with scale & rust clogging up the coolers? Stbd motor was pretty clean inside but I pulled out 2/3rds quart of rust chips & dust from the water jackets using a magnet while the heads were off. That explains why that engine always heated up faster. Currently looking at Evaporust and their other product Thermocure, and thinking to fill up the blocks and let it sit awhile before conversion.

2-Found a schematic on how 1/2 closed cooling systems are setup, it looks pretty straightforward. I'll need a new thermostat housing which sends coolant to the heat exchanger when its open rather than bypass to the exhaust & sending back to the circulating pump. Can I just use a thermostat with a drilled hole so that the circulating pump isnt deadheading the coolant?

I had two blocks that were raw water cooled, hot tanked, then soaked in a 55 gallon bucket of purple power, pressure washed, sat full of evaporust and vinegar alternately, and could not get the rust scale out in any meaningful capacity. Ended up taking a drill and some frayed heavy strand SS cable along with some long screw drivers and spend two days scraping and breaking all of it loose and vacuumed out, then a final pressure wash. I got over three qts of scale out from the pair of blocks in the end. it was difficult but now that they are cleaned out it was real obvious why I was having cooling problems.

I cannot image doing that with the rotating assembly still in it, it involved lots of flipping and rotating the block on the stand and was a total mess.

Distilled water will pull the salt out. Run only distilled water in the cooling system and drain it after each outing. I added antifreeze after the 4th trip. No issues.

I did the distilled water route when I converted mine. Several flush cycles, but my motors were relatively clean.

I hear you on the astetics, but I got used to it quickly....

Can't tell, but are you running a full system?.....how much hp are you cooling?......is that a Harden closed cooling system?......not an eyesore, looks pretty good!

That's a half system. It's the CP performance kit (which I think is the same as the Hardin). FYI their system fits both standard decks and tall decks (mine are tall decks, and they mocked it up in their shop to confirm it fit before they shipped it). I'm cooling 800 HP. I have never seen the temps budge off 150* even when oil temps have gotten to 220-230 in 100 degree heat.

I was REALLY upset about disrupting the looks of the front of the engine but got over it instantly and will say it was the BEST money I have ever spent on upgrades. It's nice to have them mounted on the engine - if you have to yank the motors out it's one less thing to deal with and just comes out as a unit.

Park35 has a badass set up too. If you search his recent posts you can see his....

I to have tall deck BBC'S w/AS&M EFI'S just trying to imagine the physical layout of a full system......I spoke with Rick @ CP Performance and they have a full system in stock, but I believe it's good up until 650hp...I'm just over that with 700hp.
Rick quoted cost of full system is in excess of $2500...right now following a tread......"closed cooling for 1000 hp" or something like that, but dealing with alternative coolers (Detroit diesel dd15 coolers) .........interesting, but it involves some fabrications.

Gen VI 502s… I scraped the insides and tapped on the blocks for a couple weeks while cleaning and taking measurements. Then I prayed that the blocks would pass a porosity test (they did). Easily 3/4 off, to a gallon of scale and rusty chips/flakes and then I washed them with purple power and vinegar. Finally, the blocks were pressure cleaned and tanked.

Crap still ran out of them at the first start up.

I drained the systems after that, and once in the boat, they were filled and have been fine since.

Flush flush flush and flush again. And then flush some more.

These are Merc 454/502 heat exchangers on my 509s. Running 600+ and the temps drop into the 150 range at speed. I got mine from Mike, too.

here’s a full closed diagram…



https://images.search.yahoo.com/sear...g&action=click

mine was a fresh build straight out of parts washer and into a antifreeze/distilled 50/50 on full closed diagram. I did flush it and then refilled the coolant after breakin.

now it’s just flushing with salt away on the heat exchangers etc… no way salt water is getting my block, unless it grenades,,,