ecuchips's posts & fabrication for big hp seems to be in the capacity for a 1100hp application .....but like yourself, I also don't have the skill set.....he's halfway around the world!

Have you tried contacting Orca Marine ? They make industrial sized heat exchangers and many replacements as well. Just a thought

I'm still on the drawing board on what to do. Don't 'need' them just yet. The DD15 is 304 stainless housing with 316 tubes. Hot salt water and 304 stainless do no go well together. Zincs would be required for sure. Hot salt water needs titanium to be impervious. Even 316L does not like hot salt water.

I don't see the raw water getting too hot in the exchanger.

I was investigating fabricating stainless from raw materials vs the modded DD15. It's more about access to the stainless tube.

Are you twins or single? Why not run 2 exchangers in series to get your 1100hp capacity?

I appreciate everyone's thoughts above. I'm running a single. I would certainly run two in series, I just could not find any evidence of people doing that elsewhere (maybe I was picking the wrong keywords) and was hoping to get some validation before trying that. This is for a racing application so cooling is of course a huge consideration I don't want to get wrong. I will try to look into that further to see what people have done.

I would call innovation marine or Bam. I think they both ran closed cooled systems in engines that big years ago....

When in series, a dual heat exchanger would likely add some flow restriction. You'll have a circ pump on the engine, it should be ok for flow.

Raw water pump only has to pump through the exchangers...an oil cooler, PS cooler, maybe a trans cooler...then into the exhaust manifolds. No engine block/head flow restriction of a raw water cooled setup. Should be easier on the raw water pump.

A single would be far better for sure.

Not sure if that`s what youre asking but I run 2 coolers in series for oil.
Bellhousing cooler then to tube cooler.
I could have gone with a smaller cooler, the temps stay around 130ish cruising and 160ish at wot

https://cimg0.ibsrv.net/gimg/www.off...1af138878f.jpg
https://cimg7.ibsrv.net/gimg/www.off...20a885a9aa.jpg

On the Mercury 700's all of the coolers (engine oil, PS, tranny, fuel) get raw water. The only thing the exchanger with antifreeze is feeding is the engine block itself.

I would think the exchanger for the QC4V 1650 would be plenty adequate for any blower motor above 1000hp:

Cooling Components (mercruiserparts.com)

I spoke to Innovation and unfortunately they don't have any solutions north of 800hp. I spoke to Hardin a few months ago and they also didn't have any solutions. Will chat with Bam tomorrow.

302Sport - I had the same thought and was going through those parts catalogs last year. I think it is a potentially great solution. I don't see why it wouldn't work, but was hoping to at least pick a solution that confirmed worked for someone before investing the time, energy, and money to set it up and then potentially having to go back to square one. Perhaps I'll be the first to take the jump...

Yes I will be feeding raw water for everything else - antifreeze only for the engine.

I really like how ecuchips has that additional outlet in his heat exchanger for the ballast fill. I run a ballast tank that has an additional pickup on the transom, so another option would be two heat exchangers in series that each draw from one of my pickups and then can 'steal' from one of them when I fill my ballast. Could play around with multi stage water pumps to split the water (from one pickup) between each exchanger or even two water pumps, one for each exchangers, using both pickups. Spitballing ideas to overcome potential flow/restriction issues... Haven't thought the whole thing through so hopefully those ideas aren't too dumb.