Another Reversion issue with Gil Risers
 

I have a pr. of 540's built from base Merc 502's w/ Scat stroker kits. They are otherwise built out the same as 500 efi's w/ the same Crane cam, Edelbrok Alum. heads, 500 efi intake and injection system, gil exhaust. When I built them a few years ago I bought new Gil manifolds and a used set of Gil "shorty" risers that I had extended with inner and out pipes so they were dry out to the transom and added O2 bungs. Well, the risers started springing leaks- I guess galvanic corrosion form the previous owner not flushing in salt water so I bought 2 sets of almost-new current style BB Bravo wet exhaust risers. They're the exact same ones Hardin marine currently sell on their website which says "This same system is also used on Mercury hi-performance 525SC and HP500-engine packages as standard equipment from Mercury Hi-Performance." When I read that I assumed they were designed not to revert even though they were shorter and a little lower than the ones I had fabricated. As you might have guessed, I got huge dose of reversion in one engine the second time out this year. Curiously, I can't find any evidence of water in the other engine. After eliminating any other possible source of raw water leak- pressure tested the manifolds and oil cooler @ 60 lbs and the blocks are closed cooled, I called Hardin to inquire if it could be reversion. The technician acted like a total jerk and implied I was a complete idiot for running those risers on 500 hp or efi engines. So 2 questions: is he right about these risers reverting with these engines, and more importantly: if I have them extended dry to the transom again I assume this will fix the problem?

So the manifolds passed with flying colors it sounds. You shouldn't feel like an idiot or have been treated like one for using your current risers, I've seen some wicked builds with less. I know what risers your talking about and would like to know why the guy you talked to completely contradicted what their website indicates. So the risers you have are used in new condition? Also did you inspect them well for any flaws, cracks, etc? Isn't that came on a 114 lsa? I've seen several of the same risers with 500/525's. Are you using the turbulaters?

Go dry and make friends that's my opinion...

I looked on Hardins site but wanted to confirm what risers your using. If you can't post let me know and I will post a couple different ones and you can confirm. I just can't see why you'd have an issue.

Here's the link to the risers page.
http://www.hardin-marine.com/p-12815...re-system.aspx
The quote I'm referring to is at the end of the first paragraph. I sent an email to Hardin complaining about my experience and got a reply basically saying that no they would never recommend using those risers with a Hi-perf 500 or 525 but were just pointing out that Merc did! Why they would put that on their website if they as the manufacturer of the product feel it's not mechanically sound is misleading, irresponsible and beyond stupid in my opinion.

To answer your other questions, yes the oil cooler and both manifolds held 60 lbs indefinitely. The risers are in new condition. I already had O2 bungs installed- a perfect weld. In fact I managed to get a little pressure in them by stuffing a deflated ball in the exhaust end, inflating it against where the water dump holes are and pressurizing the water jacket with a compressor- it was't a perfect seal but I was able to keep enough positive pressure to spray soapy water all over the weld areas to confirm there were no leaks. I'm gonna take these risers to my mig welder and have him extend the inner pipes 15". If Hardin's website hadn't misled me I probably would have just purchased dry pipes to begin with.
As to why it's happening severely on 1 engine and not at all or at least not noticeably on the other is a mystery.

If you scroll down you'll see the HP500 replacement.

Here's the deal:
Merc had reversion issues with the Gil's with standard risers. Years later, and multi TSB's later, they came out with the taller riser. It worked a lot better, but some still got a little reversion. The HP500 was the last Blue Motor to get Gill's.

Link: http://www.hardin-marine.com/p-15730...st-system.aspx

Pic of the later HP500 tall risers
: http://www.hardin-marine.com/images/...420-901019.jpg

I saw those risers but they would never fit under my hatch. I know Merc had reversion issues with Gils several years ago but assumed (incorrectly I guess) that that was with the old style "shorties". Because it referenced the HP500 and 525sc in the description I thought that it was the new design they came up with to address the reversion issue. Now I'm wondering what BB engine WOULD be safe with the Bravo style?? Seems like they'd be marginal even in a standard black motor if they reverted that bad in mine-

What is the most practical thing for you to do at the moment. I understand your frustration however we all have at one point or another in this wonderful world of offshore. It's a riot so we somehow manage to get through it. Can you find some dry tails reasonable? Other option would be to call bob m and have him design and build a set of cams that would compliment your exhaust however I'm afraid he'd be very much on the conservative side considering your current situation. Go dry or get high and sleep on on it. Just know we all feel your frustration.

http://www.ebay.com/itm/4-Stainless-...UAAOSwz2lXCsdX he has others also

Perfect

Those tails on ebay wouldn't fit under my hatch. I'm gonna take mine this morning to a mig welder and have him extend the inner pipes 15". Thanks for the suggestions and yeah, I know, this kind of stuff is part of the charm of performance boating. I still think Hardin needs to take that description off their website if they don't stand behind what it says.