Headers and Risers Leaking on 502 Mag

[ltl_mac2000]

Looking for some opinions to make sure I don't get ripped off and the job gets done the right way.

I have a 502 Mag in a 99 22ZX with 110 hrs. I fresh water flush every time I run the boat. This season I have been seeing a lot of rust around the risers and the manifold but up until last week, I never actually saw any water leaking.

Yesterday, after a detailed inspection, I can actually see about a 1/4 diameter hole in the Starboard manifold, and see a significant amount of corrosion around the manifol near the spark plugs.

1st...Is this normal in a 6 year old boat that gets fresh water flushed?

2nd...Should I not be running the boat at all until it gets fixed? I have read some of your comments about how water can get into the engine. I don't really understand how that could happen but would def like to. As best I can see, any water or exhaust that is coming through that hole would being going out the exhaust anyway? Any comments on this would be great.

3rd...Approximately how much should I expect to pay to get this fixed. As much as I would like to attempt to do this myself, I think there is too much that could go wrong in the process. Especially based on the working room around the engine and the amount of corrosion on the bolts. Plus, I would like the run the boat again before next summer. The marina that I store the boat is supposed to get a look at it today or tomorrow. I would like to get some of your opinions and experiences w/ this so I know whether I am getting ripped off or not. Anyone have any particular opinions on what should get replaced and if I should use aftermarket parts rather than Merc parts. If the risers are good but the manifolds are not, should they both get done at the same time? Stuff like that.

Thanks in advance for the help. There is a lot of knowledge floating around on this site, and I look forward to hearing your thoughts.

Danny

[thriller]

Simple to do, I did it myself.

Your cost around 2000 bones!

Use the after market Stainless Marine setup. Call Brownie direct and he will accept payment via credit card and shipp everything to your door including the new chrome risers, gaskets and all the fittings, hoses and gasket cement.

The old cast iron ones rust whether you boat in salt or fresh water.
The plus side is the new ones are lighter and add a little bling to your motor. They also produce a few more HP and a couple of MPH. More torque too!

You can also buy them and have someone put them on.

Call Stainless Marine and you will be glad you did:wink:

Mike

[Morgan's Cloud]

Same engine, same year , about 147 hrs. Caught it just in time. Pulled the manifolds off to replace them with decent stainless ones before we got bit hard only to find water (salt) had puddled in about three of the spreaders.
That was a close call !
As Mike said, your going to experience this wether your in fresh or salt.And if you replace with the stock Merc junk it will just happen again. One can only guess at how many warranty claims that Merc had to pay before they did the redesign.
Definitely bite the bullet and replace with reputable stainless ones
Steve

[oldandtired]

It is a do-it-yourself job until the bolt heads are totally trashed. If the bolt heads are solid, with only surface corrosion, then it's not a difficult job. If they are totally wasted, then you better have some serious patience or farm the job out. Upgrading the exhaust is a no-brainer. Which system you go with can be more complicated. For most people who aren't mechanics but are going to do it themselves, I think that the stainless marine setup is nice. Headers are great, but sometimes the brackets can be a hassle plus they are more expensive. The Dana system looks great and is a relative bargain. I went with CMI Tube tops on mine and it was kind of a pain to install and cut the transom, but they look and sound great. I picked up 2-300 rpm with only the headers on my 22zx/502 Mag.

Rene

[Cuda]

You can buy a Revolution exhaust system for under $900. Stainless marine may be better, but you can buy two sets of Rev's for the same money. I think they look better too. Just in case you weren't aware, the Stainless Marine exhaust is made of aluminum also. I've heard they have never had a failure due to corrosion.

[CrackerJack]

This happened on our engine, but we didn't catch it until we got saltwater in 5 of the 6 cyclinders. After this happened we were talking to a Merc. rep. and he stated we should have been replacing the gaskets between the manifolds and the risers ever 200 hours, our failure was at 230 hours. I have never seen or heard of this being a required or recommend service. We now have replaced the engine with a 5.7L and a Stainless Marine setup. Taking the old units off will be the biggest challenge, installing the new Stainless Marine units should be easier. We are very happy with the Stainless Marine units, plus they look great. I talked to Brownie and gave him the measurements of our set up and the installation went perfect. This was our first time doing an engine replacement. Go with Stainless Marine.:yes:

[blackhawk]

ltl_mac2000, there are quite a few good companies out there. Like Cuda said the revolutions are a great bang for the buck. But the Stainless Marine's will be better quality at twice the price. The Danas look good too and they actually continue the seperate runners THROUGH the riser. This has definitely peaked my interest. There's also CMIs, more $$$ but a true header design. EMI, IMCO, etc.

thriller, is your 502 stock? Did you see any performance gains with just the manifolds?

oldandtired you said you picked up 200-300 rpm. Did you also picked up a couple mph?

[Kirbyvv]

I went with EMI Thunder exhaust, also picked up about 300 rpm. Went with a higher pitched prop to bring the rpm's back down and gained about 6 mph in the process.

[ltl_mac2000]

I spoke to Brownie, and he seemed really knowledgable. Sounds like his stuff is a little more expensive than some of the competitors, but seems liek the quality and ease of replacement makes up for it.

Being that I am not very knowledgable about the exhaust systems, can anyone explain or point me to a document that explains why you gain the extra HP. Looks like something to do w/ Back Pressure and Reversion, but I would like to understand this a little better.

Also, why w/ the extra RPM are you changing props, is it to avoid a max RPM. If so, what RPM should I be looking to change Prop's at w/ the 502Mag?

[Cuda]

If you have problems removing the bolts from the old exhaust manifolds (rusted off, rounded out, etc), just grind the bolt heads off, pull the old manifolds, and then you can remove the bolts with either a GOOD pair of vice gripes, or a GOOD small pipe wrench. Been there, done that.

[oldandtired]

Hey Blackhawk,

I picked up about 3 mph. I would like to mess with the fuel injection a bit, but I think that I'm in the ballpark for my boat at 75.7mph gps.

Danny,

You need to reprop any time that you get away from your peak power which should be right around 5000 rpm on that engine. So, if you were turning 4800 peak rpm and picked up 250, you wouldn't want to touch anything. But if you were turning 5000 and are now up against the rev limiter, then you obviously should do something. Even if you got rid of the rev limiter and could hit 5300, you would still want to raise your pitch so that your rpm gets back to about 5000 which is where peak power is on that engine.

Rene

[RedDog]

what RPM should I be looking to change Prop's at w/ the 502Mag?

I believe your 502MAG has a RPM limiter that holds it back to 5150 RPM. So if you start to bounce off of the limiter, a bigger prop would be in order

[ltl_mac2000]

Thanks for all the help guys. I ordered the "Risers/Headers/etc" setup from Brownie at Stainless Marine. Stuff should be here on Friday. Hope to have installed by next week.

I will be sure to post the outcome of performance once I have installed everything.

Danny

[Cuda]

Thanks for all the help guys. I ordered the "Risers/Headers/etc" setup from Brownie at Stainless Marine. Stuff should be here on Friday. Hope to have installed by next week.
I will be sure to post the outcome of performance once I have installed everything.
Danny
You can't go wrong with either SM or Brownie.