View Full Version : Exhaust Manifold replacement help

ProStar Slalom
02-09-2012, 05:58 AM
Fellow TTers,

I got home yesterday after a year in Afghanistan and am already looking forward to some spring projects. While home for a couple of weeks last summer I noticed that our '84 had developed a small leak on an exhaust manifold that had been repaired by the previous owner with JB Weld.

The engine is a PCM 351, and I'm betting that the manifolds have never been off the engine (1200+ hrs). Risers look good but manifolds of course have quite a bit of rust as well as the JB Weld patch.

So, I'm thinking it's time to replace the exhaust manifolds, but plan to keep the risers unless they look really bad inside upon removal. A few questions that will be easy to answer for several of you:

1. Planning to buy new manifold and riser bolts unless someone tells me it's a total waste of money? Quite a bit of rust on existing hardware.

2. For manifold gaskets and riser gaskets, what sealant do I use with them, if any?

3. What are the torque specs for manifold bolts and riser bolts?

4. Anything else I should do while the manifolds are off? I'll probably replace plugs since they'll be easy to get to, and debating replacing points with points or EI....but don't want to start that debate here. :)

Thanks in advance for the help.

02-10-2012, 11:23 PM
First, welcome back and thanks for your service.

As for your manifolds, it is not a technically challenging job. However, it can be a bit of a pain. I did this once on my old 87 PS 190. The problem I ran into was the bolt heads had rusted off and I couldn't get a tool onto them. I ended up having to cut one of the jackets off with a saw-z-all and use channel locks to get the bolt out. Also, you'll either need a floor jack or an extra set of hands to hold the manifold up once the bolts are out so that it doesn't drop.

Discount Inboard Marine has everything you need:


Good luck.

02-11-2012, 10:57 AM
I used new hardware when I pulled mine. Very inexpensive. I bought the manifold install kit from skidim, and indmar riser kit (gasket + new hardware).

Fortunately all of my risers / manifolds came right off with no hassle.

The iron manifolds are HEAVY and and you will probably curse a bit putting them back on, trying to keep gasket lined up while fitting bolts. A helper would have been nice for me. Easy work, just cumbersome.

All of the old hardware was slightly corroded (probably original). New, strong SS hardware is cheap insurance and just part of the freshening up of an older boat.

I would be sick to try to reuse old hardware and have something like shearing a bolt while torquing happen when reinstalling, creating a huge hassle (over just a few bucks saved).

02-11-2012, 10:50 PM
To make exhaust manifold replacement easier, use a couple philips head screwdrivers in bolt holes on either end of the manifold to keep it line up while you get bolts in place and started. I have changed several by myself using this method. Makes it pretty simple.

ProStar Slalom
02-12-2012, 05:28 AM
Thanks for the feedback, guys. Anyone know the torque specs? What gasket sealer, if any, should I use for manifolds and risers?