Smoking gun. The first marine small block I built had the same problem and I went through the same thing until Nickerson explained "reversion" to me. Headers and dry to the tip through the hull tails cured the milkshakes. Lesson learned.

You said one engine had more water in the oil...
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Is the raiser with the dam missing complete on the engine with more water in oil?

yes, reversion dams.
yes, important.

Mentioned earlier in the thread… the 525 cams had issues with reversion. II’s only made worse with the smaller motor. Combine that with the TRS conversion, the water volume, and dam problem, I’m pretty sure you can pinpoint the whole thing to them sucking water.

The supercharged 454 that I had in one of my Formulas reverted water with that cam. I solved it some with some long SM risers, but it never was completely right. I would keep idle up and occasionally rev it during low speed to keep it clear.

What’s your engine idle at? Maybe you can have the fans replaced and then put them back on and increase the idle speed. Could also have the risers lengthened to run outside the transom and exist either semi-dry with dumps (will sound bad ass).

Looking at pics of how the risers have that boot attached at transom fitting, looks almost straight out.

Would he not just simply be able to weld on to the inner exhaust pipe and extend that portion only, slide it through the transom fitting and make it flush with the end. Then hook the book back up. That would then make his exhaust truely dry to the tip. Would think that would add about another 8” of exhaust pipe.

not sure it would cause a reversion problem but the newer stainless marine manifolds only have one port on the bottom. On the ones that have two water ports on the bottom you are supposed to use the one opposite of the upper, so normally water goes in the rear port fill the manifold and exit the top front.If you used the front lower port then water could push straight up and exit without filling the rear part of the manifolds.

I think the way it's setup in the photo...is one hose feeds raw water when the thermostat is closed. When it opens, it flows both hoses.

Otherwise there is no flow through the system until the thermostat opens up.

^^^^ you have it right,water to manifold until the themostat opens up

I know somebody out there has got to have a set of old risers from a TRS boat they re did LOL stainless marine! I’m on the hunt! Got my quote of them and I still haven’t processed it mentally yet LOL

thanks guys!

Made my order with stainless marine 6/4/24 for new risers and everything else. They built them and got the call today 6/11/24 they are shipped out! Fingers crossed I finally get to the bottom of this tail chasing engine rebuilding game.