WARNING: Brand new OEM Merc manifold casting cracks

I didn't have risers on my previous boat so I didn't need to get the rod tightened. But my friend, who's done it 100 times (and who broke two castings) uses the nut technique. As long as you don't exceed the torque spec (25ft-lb? 30 ft-lb?), you'll be fine. JUST CLEAN THE THREADS on the rods/bolts and inside the new castings!
 
I got a loaner thread chaser from the autoparts store. It's strange, I chased the studs, and the holes to the point where the chaser goes in and out with my fingers, but as soon as I get one turn on the stud IN the hole it requires all my strength to tighten a 10" vice grip on it and turn it without the vice grip slipping. I can still only get a little over half the threads into the holes??? It seems to be the same thread because I'm using the same chaser size on the stud and the hole. They're supposed to be sending me a new manifold in a few days, but this is just crazy hard... I'm going to try double-nutting it today and see if that works better, but I'm not hopeful.
 
Double-nutting, screwing it in part way, back out, and then back in, finally got it in all the way. Man I was nervous torquing that thing down to 33ft-lbs, but nothing broke...this time.
 
I'm glad I saw this thread, I just tried to do this job last night put it all together and went to torque the nuts on the studs and popped the casting on one of the four corners on the first side I tried. I'm telling you I had those studs as far in as I could and they fought the whole way with that loctite on them. I didn't even get close to 33 ft/lb and it popped. Getting a replacement tomorrow and I'm going to chase every thread. Any other suggestions, did everyone else just use vice grips to get those studs in? Is this how a merc tech would do it? I was furious last night set me back 2 days. Also, i was told by a merc tech to use perfect seal on every gasket and threaded bolt. He also told me to scrape the paint off the gasketeted joints because t cracks and flakes and causes voids. Let me tell you that paint is tough to get off...Jesus you buy OEM parts and basically have to re-machine them before you put them on...seems crazy...
 
Do any of these OEM suppliers provide an instruction sheet telling you to prep these before installation? You'd think a little instruction sheet might be helpful instead of sending out replacement parts at no charge....
 
Makes me wonder if they are doing that at the factory or if there are boats out there with cracked manifolds.
 
Brad Fraser said:
I'm glad I saw this thread, I just tried to do this job last night put it all together and went to torque the nuts on the studs and popped the casting on one of the four corners on the first side I tried. I'm telling you I had those studs as far in as I could and they fought the whole way with that loctite on them. I didn't even get close to 33 ft/lb and it popped. Getting a replacement tomorrow and I'm going to chase every thread. Any other suggestions, did everyone else just use vice grips to get those studs in? Is this how a merc tech would do it? I was furious last night set me back 2 days. Also, i was told by a merc tech to use perfect seal on every gasket and threaded bolt. He also told me to scrape the paint off the gasketeted joints because t cracks and flakes and causes voids. Let me tell you that paint is tough to get off...Jesus you buy OEM parts and basically have to re-machine them before you put them on...seems crazy...
Click to expand...

Great post I will be changing manifolds and risers at the end of this summer guess I'll order them early to inspect them & re-machine.
It's called poor or NO quality control there is no reason for any part to make it to a consumer that's out of spec, sounds like Mercruiser has a quality issue no part should ever be shipped that needs to be re-inspected by the end user. Service manual even states to inspect for flatness file flat if necessary. I would always check thread and mating surfaces but for the cost of their OEM parts why should we inspect their work.

From SERVICE MANUAL

Cleaning and Inspection
1. Clean gasket material from all surfaces and wash parts in solvent.
2. Check water passages for foreign material. Passages must be clean for efficient cooling.
3. If more thorough inspection is desired, pipe plugs may be removed from exhaust manifold and exhaust elbow.
IMPORTANT: If plugs are removed, coat threads with Quicksilver Perfect Seal before reinstalling.
4. Check for cracks.
5. To test manifold body for leaks, block-off plates, plugs or short hoses with plugged ends must be used. One block-off plate must have a threaded hole for attaching compressed air hose. Use new gaskets when installing block-off plate(s). Apply 40 psi (276 kPa) of air pressure and submerge manifold in water. Air bubbles will indicate a leak.
6. Inspect all parts carefully. Machined surfaces must be clean and free of all marks and deep scratches, or water and exhaust leaks may result.
7. Check the flatness of all gasket surfaces. Maximum overall is .003 in. (0.07 mm), with not more than a .001 in. (0.02 mm) difference within 1in. (25 mm).
NOTE: Maximum material that can be removed is .010 in. (0.25 mm) to true a gasket surface up. When torquing the attaching bolts, make sure that they are not bottoming out in the manifold’s threaded hole.
 
Called my local Sea Ray dealer / OEM supplier and told him, he didn't even seem surprised which was my first red flag. He wants me to bring it in today so he can look at it, they better give me a new one for free. I tried emery cloth to get the paint off and that took forever, ended up buying a wire wheel for a drill and that made pretty quick work of it, but still. You would think that if they weren't supposed to be painted they would've taped it off. Also, that red Loctite on the threads if it causes this much of an issue, you would think they wouldn't add it anymore. Now it's a new manifold and all new gaskets for the whole side, and starting all over again. I'll keep everyone posted on if they cover the cost...
 
YES!!!! Chase the threads in the manifold with a tap and use a die to remove that red crap on the bolts, or just re-use your old bolts but still use a die on them.

I never put Perfect Seal or any other sealant on the threads. They do nothing to contain water so it's not necessary and the manual does not call for it. Make sure all the threads are spiffy clean and the mating surfaces are immaculate.

The wire brush was the right move! Mercury has a proven track record of painting everything is sight. As evidenced by the Cool Fuel 3 debacle.

To tighten the long bolts don't use a vice grip. Use two nuts tightened down onto each other (as described in post #24 above. Then drive each one in. Pain in the butt but it works.
 
Update: Brought the manifold back on Friday and had three mechanics look at it to "make sure it wasn't my fault" ... They had never seen that happen before and ordered me a new replacement manifold, all new gaskets and all new studs no charge. Brought it home and tapped the manifold and was surprised at how bad the factory thread job was. Out of curiosity tried to screw in the studs and it was still terrible. Put a die on all the studs, not only did all the Loctite come off, I was amazed at the metal that the die cut off, the studs were way worse than the manifold threads. When this was done, everything went together so smooth, studs threaded into the manifold with ease. No broken castings, really wish I saw this thread before I started, but sure helped out afterwards. Thanks for everyone's input and help on this one!
 
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