Manifold Cleaning

[Tucker]

Hi guy's,
I have a 1995 Sea Ray with 5.7L Mercruisers. The engines are F/W cooled on the engine block only. The manifolds are raw water cooled. I boat on the Northern Chesapeake and the water is brackish. I want to convert the manifolds over to fresh water cooling. Without taking off the manifolds, what is the best way to clean rust and scale from the water jackets. I e-mailed Preston to ask if a soaking with the Super flush highly concentrated would work but haven't heard back. The plan is to remove the risers and block off the water passages. remove intake plug cap the exit plug and just fill 'er up with the radiator cleaner. Anyone performed this conversion before and if so did they bother to clean out the exhaust manifolds before adding the kit. I'm concerned about rust and scale clogging the heat exchanger. Any comments guy's?? Thanks

[Corpus Skipper]

They have to come off for the conversion anyway. Just clean any loose scale out of them by flushing with water, then blow out with compressed air, giving them a good tapping with a rubber or wood mallet once in a while. Inspect them well, Merc risers are famous for short life spans.

[gonzo]

Risers have a 3-4 year life expectancy. If you lflushed and maintain them well, maybe a bit longer. I see no problem with flushing the block. Radiator cleaner is designed to do that.