Thanks for the support...Yes, I pressure test my headers religiously; that was the first thing I thought when I saw the salt in the ports but they're not leaking; I tested them every way possible... submerged in water with 70 psi in the jackets, not a single bubble... filled them with water and then heated the primaries with a propane torch, not a drop. it's all from reversion... and the damage in the same cylinders on both engines supports that theory as well. Yes, it completely sucks to have to go through some pretty big expenses to correct a major design flaw but believe it or not, I'm kinda feeling lucky in a twisted way... I easily could have lost both rear engines (I've already replaced one long block) plus have to do all of the stuff I'm doing right now and potentially lose a good part of next season. And hey, it's winter... gotta have something to do ....

525's are bulletproof!!!

Just an FYI, the stock springs are not ISKY's, they are made by PAC.

We've seen quite a bit of reversion issues with silent choice as well. All of them could be traced back to either a cracked tailpipe or a broken, cracked or missing dam in the tail. In all of the tails that run silent choice, there needs to be a dam welded in the floor of the pipe to stop the water from creeping back up the floor of the pipe and into the header. It will not work without it and is a given that it will revert water. They have a bad tendency to come loose or break off completely. It really doesn't seem to matter much if you use the silent choice or not, unless you try to run wide open with it. Having it either open or closed at idle doesn't really matter. The water is still introduced too early. The dam typically runs from about 4 o'clock to about 8 o'clock. It's actually a small section of pipe and forms a pocket to catch the water. It gets welded near the flange and extends into the tail about 3" or so and is elevated off the floor of the pipe about 1/4" or so. As the water tries to climb back up the floor of the tail, it goes under that dam and stops where it is welded. That's why you will have some reversion if that weld breaks as there is nothing left to stop the water.
Eddie

Eddie do you happen to have a picture of the "dam"
Thanks!
Steve

I was thinking about it when I posted earlier. I will have to look through my pics and see. I just repaired one last week. It had completely broken loose and got wedged in the silent choice flapper and got all bent up. I had to do quite a bit of straightening to get it to go in place before I could weld it back in. I don't think I took any pics of that particular one. I'll see what I can find.
Eddie

Mine is getting new springs, retainers and keepers now. The headers are off. When I get the boat home I will look for those dams. Eddie, it's not getting the Isky springs I don't think. They are from Teague and supposed to be stock replacements.

I half ass drew this up. I hope it makes sense. I call it a dam for simplicity. I'm not really sure what else to call it.
It is welded only right near the end of the tail closest to the header. The rest of it sits only about 1/4" or so above the floor of the pipe so that any water that does climb back up the pipe will hit the end where it's welded and won't be able to go any further. The water would have to be deeper than 1/4" for it to get past the dam.
Eddie

Gotcha. When you mentioned ISKY's in your post, I assumed that you were using them. I remember you saying that you were going with the Merc stuff in earlier posts, so I was a little confused.

Hi, I am a first time 525 owner and reading all this makes me nervous! 2007 Baja 35 Outlaw, bought in Aug with 97 freshwater hours, most below 3000 rpm. Boat was surveyed and passed compression test. Had new plugs installedd since old ones were out. Anyone able to brag about 500 trouble free hours or anything like that? With the thousands of 525s in use, there has to be an equal number of great stories to horror stories. Right?

The 525 is a great motor and there are plenty of guys out there that have run them for 100's of hours. But there are weaknesses and if you are educated and aware of them, you can prevent the major issues from occurring. My reversion issues are a combination of the silent choice exhaust setup and the 525's cam characteristics. My center engine is just fine..

I'm not sure why you say the compression test passed with new plugs... the plugs should be out of the engine when a compression test is being done. If the buyer replaced the plugs just before the survey, that would be a red flag to me... As a new 525 owner, you MUST, MUST, MUST pressure test those headers... aside from that, read these threads; they will tell you what you need to know about the other weaknesses..

Thanks, I just clarified my post. Plugs pulled, comp test performed and passed, new plugs installed....

Eddie, isn't that "dam" a complete circle and a little longer than in your sketch? This is my set-up and it has been trouble free. The top of the downspout is nowhere near the water line. Since my headers never get hot I did not remove the restricters. Wouldn't removing those increase the volume of water being dumped into the tail?

http://i763.photobucket.com/albums/x...s312Medium.jpg

Carl the dam Eddie is talking about is made into the diverter itself, yours are there and in good shape. I have serviced several 525 EFI's and Carl is right about his being in excellent condition with perfect bleed down #'s and zero sign of reversion or any type of abnormal wear to valve train. I discussed doing the Isky conversion from the start with Carl but as they say "its his boat" and I have to agree with him that for him it has worked and held up very well. By the way Carl we were shorted 1 keeper that might show up today.I always lay out and count parts before I start.....thank god this time or there would have been an engine teardown looking for the missing keeper.

First, the "dam" Eddie is referring to is an anti-reversion cone. If you look down the tailpipe from inside the boat, you will see what looks like the end of a trumpet. It is a tapered cone that has a hole at the end. This is designed to prevent the water from creeping up the pipe into the collector.

Second, I don't think you are understanding the reversion problem correctly.. The issue has nothing to do with the water line. The exhaust water enters the tailpipe through the bung on the tailpipe end of the jumper hose. Inside the tail, there is an inner assembly (a "swedge") that is pressed up against the inner wall of the tailpipe and it carries that water down the tailpipe and it exits at the end of that swedge. Because of the Silent Choice, the tail has a hole where the water and exhaust go down the "Z" pipe to the "Y" pipe on the transom. Because of that hole, the swedge ends very close to the collector. Look at your picture.. the water is entering the exhaust stream only a few inches from the collector... this is where it gets sucked back in.. Without silent choice, that swedge can end much closer to the transom putting it far away from the collector.

Third, with respect to the restrictor. You need to leave the restrictor in the top bung connected to the jumper hose from the header. This is important to maintain good water pressure in the header. What you need to do is remove the bypass hose that is running from the end of the header to the underside of your tailpipe. Plug the tailpipe bung with a SS 3/8" NPT plug and plug the header with a SS 3/4" NPT plug. This is the Mercury Service Bulletin to maintain better pressure in the header. The bypass hose allows too much water to escape too fast. Maintaining strong water pressure is ABSOLUTELY essential with these headers. Keeping them cool is the most important thing you can do.

I have never seen a dam that is a full circle. They have all been just less than half a circle. They are also about 4" long or so. The dam ends before the point at which the water enters.

You will increase water volume by removing the restrictors, but you may drop the pressure too low. The PCM has a window programmed into it that dictates what the water pressure must be. If it's not in that window, it will send it into power reduction. There is really only one way to find out and that's by removing them. Another thing to consider before removing them. That additional water would be great to keep the headers cool, but it may also be too much for the tails and could potentially cause some reversion. If it's worked fine for this long, I think I would leave it be.
Eddie

I just noticed the bypass hose is still there on the rear of the header distribution tube. You want to remove that and plug the hole in the end of the tube and tail. That allows too much water to bypass the header, which can cause them to get hot and crack. Mercury put out a TSB on that a few years ago.

Thanks for all the info. I feel my headers often and they never get too hot to hold my hands on them and that's why I've left it the way it is. I understand about the longer tails and water being introduced further back but I paid a lot of money to keep the silent choice. It was either buy those new diverters or have CMI make custom tails. Anyway it's been trouble free so I'm hesitant to change anything. I'll discuss removing the by-pass hoses with my mechanic, Brian.

Thanks for the update, Brian. No hurry on the boat. I'm enjoying the extra garage space! Will you put on a new fuel filter while it's there? I'll call you. Carl.