Extreme rust removal tips

[landover50]

I wasn't really sure where to post this question but since it's on a mercruiser motor I thought I'd post it here.

I've removed the manifolds on a 1990 mercruiser 5.7. Previous owner had cracks in the manifolds but ran it for years without repairing it (I believe they tried welding them at some point). Anyway, you can see from the pics the aftermath of his decision. I want to get it all cleaned up before I slap the new ones on. What is going to be the best way to get it cleaned up and prevent future rust as well? TIA.

 

[Rick Stephens]

The *best* way is pull the heads and sand/bead blast the scale off with protective tape on the gasket surfaces. Then have the heads tanked and gone through.

 

[landover50]

What's the "next best" way? Is there a decent way to do it on the engine?

 

[tank1949]

I wasn't really sure where to post this question but since it's on a mercruiser motor I thought I'd post it here.

I've removed the manifolds on a 1990 mercruiser 5.7. Previous owner had cracks in the manifolds but ran it for years without repairing it (I believe they tried welding them at some point). Anyway, you can see from the pics the aftermath of his decision. I want to get it all cleaned up before I slap the new ones on. What is going to be the best way to get it cleaned up and prevent future rust as well? TIA.

Salt or Fresh water motor? If salt, pitch it because the insides look like your photo. If fresh and you can access area with an air hammer to LIGHTLY chip off heavy rust, then I'd try that first followed by a cup brush, then OSPHO treatment and then prime and paint. How's your thin sheet metal oil pan? Have you examined for rust using a mirror? Years ago, a friend lost oil pressure several miles off shore due to a rusted through oil pan. Good luck!

 

[landover50]

Salt or Fresh water motor? If salt, pitch it because the insides look like your photo. If fresh and you can access area with an air hammer to LIGHTLY chip off heavy rust, then I'd try that first followed by a cup brush, then OSPHO treatment and then prime and paint. How's your thin sheet metal oil pan? Have you examined for rust using a mirror? Years ago, a friend lost oil pressure several miles off shore due to a rusted through oil pan. Good luck!

It's fresh water only, landlocked in utah. Thanks for the tips. Haven't examined the oil pan closely but I'll take a look and let you know.

 

[Scott Danforth]

I would pull the heads