rusted manifold bolts?

people have mentioned HEAT. what are most using? MAPP gas torch, propane, butane (there's a tiny little torch available)? i always forget which is hottest. i had a helluva time getting a bolt (the one at the bottom) off the shock absorber on my old ford explorer (it was there for about 6 years). a bit of heat made it a snap. of course i wasnt hanging upside down in the engine room but there was a gas tank just above and behind me! no KABOOM!

Madagascar_Penguins.PNG
 
3M cut-off wheels are the best on the market in my opinion, but typically are too big for the smaller dremels. I have them for my die grinder. They last long and make clean cuts. I'm not sure if 3M makes them for the Dremel units but if they do, I'll wager they are good. Sounds like you already have your bolts off, but I thought I'd volley this in there.
 
Frank,
I just have a little 140A wire setup. It's more portable than the boom boxes that the juvenile delinquents carried before they started stealing ipods.

Best regards,
Frank
 
The bolts on the manifolds of my 7.4L carbureted Merc are rusted on. I've gotten 13 of 16 of the bolts off by smashing on the closest socket size and that worked great. However, there is no way of getting the rest using this method. I was told to dremel the heads off the remaining 5 bolts and slip the manifolds off. I'm confident this would work well but not as confident about the sparks flying around with gas so nearby. Is their danger here? I don't feel comfortable do this. Also, the spark plugs have not been changed out in a long time and are going to be a problem to get out. But I figure if I can get the manifolds out the plugs should be a lot easier. Should I just pay the big bucks to have have the motor pulled?
Dan
 
dan
dont know what type of boat you have so we dont know what your engine room setup is. BUT, would it be possible to shut the fuel line off and let the engine run til it "runs out of gas?" then you can place some wet towels in the area of flying sparks and let the dremel rip. not sure if this is still a KABOOM risk (i'm sure others will chime in) but it seems to me there has GOT to be a better way than pulling the engine.

btw, congrats on getting the 13 out!

how old is the boat?
 
The sparks from the dremel are not very hot. They can land on your hand without burning. If you don't smell gas, there is no explosion problem. If you smell gas, fix that problem before using anything that produces a spark. Even hammering a socket onto the bolt head will produce a spark that can be dangerous in the presence of gasoline vapor.

I used a small hand held mirror to make the grinding easier. I could see what I was doing without putting my head down there. The only downside is the mirror gets eroded by the oxide hitting it from the cut-off wheel. Buy a cheap mirror for this job.

Best regards,
Frank
 
I'll second Frank's coments and add be sure to run ER blower before starting and continue while you work. You can also place damp, not dripping, bath sized towels around the area where you are working to keep the sparks from spreading too far.

Henry
 
Thank you all for your replies. I can't start the boat in this state so running the gas till it's out is not an option although I wish I would have thought of this earlier. I'll use damp towels and run the blower while do the job. I learned the mirror trick while taking the other bolts off and sure to use that again. Seems to be the way to go. Let's see if I have the guts to go for it. Thanks.
 
i spend my days drilling upside down in a mirror. it takes some getting used to but it works:grin:
 
yes. The mirrors worked great. I also heard that you can ez-out the rusted bolts or even just drill the head of the bolts off with a regular drill bit. Have you heard of this?
 
DMon,

Trying to drill a cetered hole in a corroded rounded hardened steel bolt head located basically under the engine is impossible! Banging on slightly smaller sockets, back out sockets, or griding off the bolt heads works best. It's tough to grind the heads off without damaging the manifolds. But then again, if the bolts are corroded on, the manifolds are probably shot anyway! PB blaster and a mapp gas torch on the bolt heads, after the old manifolds are banged or chiselled off, helps to loosen up the bolt studs before locking a vise grip on then. Don't force it! PB blaster and torching several times may be needed to get the bolts out. Snapping off a bolt stud can ruin your whole day! Then you have bigger problems!
 
salty
have you used a torch in the bilge? i was wondering about the feasibility about that (see post #21 above). i know that with all hatches up and no fumes present there is no danger of instant explosion, but do fumes remain in the cylinders (a inch away from the bolt head) that could create a problem? i'd imagine that heat is THE BEST option for removing corroded bolts but i wonder about safety.
 
Ron,
I use a single bottle mapp torch- the torch has a starter attached. You can buy it at Home Depot, Lowes, True Value Store, etc. A lot of plumber use this type of torch for a quick sweat fit job (including my next door plumber neighbor- he also helped me chissel off the manifold once I grinded off the corroded bolt heads). My boat mechanic friend uses it as well. The heat from the torch on the bolt heat will not affect the engine cylinders. Vent your bilge before you start. Smell for gas leaks! No gas smell, no explosion. The gas in the engine cylinders and carburator has evaporated. Just don't torch the gas lines or fuel/water filter! The torch will cause metal expansion/contraction to break the rust up in the bolt threads, as well as melt any perfect seal that may be "gluing the bolt". PB Blaster or any nut buster spray helps as well to get into the threads and free up the bolt. 6-56 or WD-40 can help as well, but not as effective. Don't spray a flammable aerosol which torching! You'll create a flame thrower! Read the can! (Don't use near open flame!)
 
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he also helped me chissel off the manifold once I grinded off the corroded bolt heads). My boat mechanic friend uses it as well.
Click to expand...

so you still had to grind the heads off even after applying heat?

i have the mapp gas bottle you describe. i've done some minor plumbing in the house AND used it to help get my props off one fall!
 
I agree with fwebster. If you can purchase a pair of stud plyers thats the ticket. Some may argue but I would get a small propane torch, (you can buy the very small portable type that run off of butane) and once you have cut off the bolt head take your time and heat the bolt up, this will work I can guarantee you, after you heat up the bolts one at a time of course, the stud plyers will remove. These stud pliers "WILL NOT SLIP" believe me. There are those that will argue a small torch like the type I told you about will not heat the bolt up enough to remove, they would be WRONG!! You do not have to heat the thing up red hot, with appropriate heat the bolts will come out. Stud pliers are a great investment and you will find use for them on many occasions. They have a jaw design that will not allow them to slip and combined with reasonable heat they will remove those bolts.
 
The dremmel worked liek a charm. Got the remaining bolts off and the manifolds came right out. The remaining studs came out easily as well. Thanks for all your help. Saved me from having the motor pulled.
 
Ron,

Some of the bolts came off without heating them, others wouldn't budge even after the heat! Some came off with the craftsman easy out sockets. If the bolt heads are totally corroded off and you can't get a easy out socket or vice grip on it, it's time for the grinder! Once the manifold was knocked off, I alternately heated and sprayed the bolt studs and engine block surrounding, and let it sit overnight where needed, until I could get the studs out with a vice grip. Result- no engine block damage and the studs came out.

I completed my upper engine rebuild, put on the new manifold, new spark plugs, distributor cap and rotor, new ignition wires, and my engine is purring like a kitten! The spark plugs should be replaced each Spring, as fogging the engine for winterizing fouls the plugs. The fuel filter should also be changed in the Spring. The distributor cap and rotor should also be checked each Spring and usually changed ($50 parts). Doing the proper maintenance prevents headaches during the boating season!
 
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Salty Dog,
You mentioned you put on the new manifolds and off you went. I just got my old bolts off and ready to rebuild. You'll see my previous messages but the short of it is I have a 1997 7.4L Mercruiser. Should I order OEM Mercruiser manifolds and risers or are Osco or Barr aftermarket parts ok? Seems like the cost difference is about $300-$400. But don't want to penny pinch if there is a difference in quality.
Also, should I just use a gasket scrapper to prep for the new manifolds and do you recommend using never seize. Seems like the hard part is done but I've never done this before so any advice would be appreciated.
 
if ya ask me (which you didnt) i would NOT NOT NOT buy aftermarket stuff. i'm not a mercruiser snob or an elitist - i do whatever i am capable of doing myself and always look at the extra cost of original parts as a non-issue b/c of the obscene amount of money i'm saving by doing the job myself.

as for prepping the mating surfaces of the manny and block, a very wise man (J Levine) once told me to expend great care in cleaning these surfaces down to the bare metal and leave NOTHING behind. scraper, razor blade, wire brush/wheel, acetone, whatever it takes (no files or hard objects) b/c the perfect seal you are trying to attain is extremely important. you dont want to take the thing off again when you find it leaking, not to mention the additional cost of a new gasket set. also, make sure you torque these things absolutely to spec. if you compress the gasket TOO much there will be leakage (i dont know the torque figure for manny bolts but can find out from jon if you want).

Just my opinion...Good luck and nice job!
 
Dmon,

Ron provided good advice! The old saying is "you get what you pay for"! I bought Merc manifolds. The mercruiser manifolds are more expensive, but they are ceramic coated on the inside- they'll last longer! Clean the mating surfaces of the engine block, riser extensions, and elbows well. Make sure the mating surfaces are smooth and have no cracks. Replace the risers and elbows if they look bad too! It's cheaper to replace them than a new engine! You can buy special emory paper from marine stores for cleaning the mating surfaces. My mechanic friend uses the green OSCO gaskets, because they have a sealant in them for a better seal. That's what I used, and I have no leaks! You can use Perfect Seal as well on the gaskets. You should coat the manifold bolts with anti-seize. Make sure you torque all bolts to the Merc specs.

Good luck!
 
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