Both motors supposedly when rebuilt were balanced and blueprinted. Now after about 20 + hrs. I have low oil pressure when warmed up and blue smoke at idle with a blueish sheen on the water. After 7 phone calls to the builder and no return call, I am having my truck mechanic pull the motor, tear it down to see what is wrong. He has pulled and worked on these motors before and is a fantastic mechanic but he is not a marine mechanic. How can I find out what the tolerances/clearances should be. These are Gen VI 502 marine crate motors with prochargers, heads ported and polished, and a valve job.

At this point this is the only person I will trust and will not waste anymore money on these reputable marine performance guys. I have been screwed over too many times.

you are in luck, here is some spec info from the man himself Mr. Teague on high perf. boat engines, he states, Generally speaking most high perf. marine engines are built with a little more clearance on bearings and piston to wall than street engines, because marine engines are under a constant load, have higher piston temps and cooler block temps, which is part of the reason, on a big block chevy marine engine run for rod clearance of .0027 to .003 inch/ Main bearing clearance for #1 through#4 set at .003 inch, the #5 main should be .0035 {thrust} piston to wall clearance depends on the piston but a forged piston with a barrel type skirt should be .0055 to .0065 inch on a fresh bore job, rering would be .0075 inch hope this helps taken from Power boat mag september 2001 . Mark

Thanks

Glad to help out!

Hey H2Xmark, I think that was my quesion about my motors in the book ! Thanks for posting it so I don't have to go dig it out . JOE

What type of 502 application is it. I know Mercs tolerances are a pretty broad range at times hence the technically correct blueprinted (within factory spec or tolerance) term in the description. But if you have something that has a tolerance spectrum of say.010 - .020 as an example, then where do think the specs should fall tight, loose, or all over the board between the two figures? I guess what I am trying to say is that if they give you a spec range then keep everything within a range within that range. Does that make sense???????

To answer your original question you can buy Merc service manuals from your local dealer or Teague has them also.

Thanks Sean.

I'm still going to call you, maybe later today. I have been a little pre-occupied.

You and me both bro.....see thread "info needed"