LAKE EFFECT

Its been awhile since I posted anything, but I stumbled across an issue this past season that I didn't think I had.

My combo is a pair of Gen6 509cid, GM aluminum bowtie heads with Manley severe duty intake/iconel exhaust valves, Merc HP525 cams, Gil HP500 exhaust, Procharger M1 blowers. I have approx. 250hrs in 10years with this combo.

My problem is I'm apparently getting a lot of reversion after extended idle times. The reason it never seemed to broadcast itself was, under my normal boating routine I don't idle a whole bunch. But after an extended time idling at the end of last season, right before I put the boat away and another extended time idling in Mentor at the SBI races this year I noticed some pretty milky looking oil.

Both motors are doing it. After 15 to 20 mins of run time at full temps, the oil looks like new again. In the past I did have a Procharger intercooler start to fail, which milked up the oil. Luckily I found it before a major issue, and replaced it. Both intercoolers have been replaced and I verified neither is leaking (plus if they were the oil wouldn't clean up).

I know Merc supposedly had reversion issues with the HP500's, and went to a different riser shortly before putting the kabash on the Gils altogether. I'm also still running the Gil turbulators.

With all that being said, here's my questions:

1) Does water fatigue Iconel valves faster than normal wear and tear would?

I mean, the reason Iconel is used in the first place is for water ingestion. I did some research on Iconel valves during my last rebuild session in 2013, and got mixed answers. Some people like to replace them during a rebuild as maintenance, but in general they don't go bad. Mine are from 1998, been in two sets of engines and have around 550hrs on them(250hrs with boost). They were all inspected and mic'ed in 2013 and deemed good. And apparently been reverted on for the past 10 years.

2) Will the taller Gil risers(Hardin Marine sells them) eliminate all reversion?

I plan on pulling the exhaust this winter and pressure checking it. The risers do have O2 bungs welded in, and could possibly started to crack around the welds.

3) Has anyone ever had a lower Gil manifold go bad?

Mine have always been used in fresh water.


LE

Black Baja

iTrader: (2)

Water is hard on the valve seats as well as rings. Things u can do that will help fight reversion... Turn up the idle, advance the cam a few degrees, less initial ignition timing (if it's locked unlock).

LAKE EFFECT

I did turn up the idle a bit. My timing is locked in at 28*. Leaning toward buying new risers, just want to make sure they will help.

Black Baja

iTrader: (2)

Just an FYI Stainless Marine sells an adapter to go from Gil to there tails. You could go dry all the way out the transom...

indysupra

iTrader: (3)

28 deg of timing on and engine that is on the edge of reversion is too much timing at idle. I run mine at 10 for that very reason.

J-Bonz

iTrader: (3)

Hey Scott,
I have seen instances in the past it's been placement of the exhaust outlets in reference to the water. I know you haul a lot. I suggest you drop all the sausage and Bud Light you haul...... just kidding bro. Hope all is well and u get this figured out.

Jr.

14 apache

iTrader: (1)

More timing the less cylinder pressure you will have at idle and it will run smother will act like a smaller camshaft.

You might be able to put a Daytona sensors cdi with a boost retard.

24* head hunter 598 at 10to1 I would run 45* at idle and engine would smooth out. And you can close the trotted plates down a bunch lowering cylinder pressure..

mike tkach

iTrader: (3)

imo the 525 cam&gills will be a problem and all the mentioned bandaids won,t do a lot of good if you have long idle times.had a similar issue with a hp500efi cam on long idle times.

mike tkach

iTrader: (3)

i do believe that will work.

jeff32

to the question '' how much reversion is too much'', I will simply answer : any reversion is too much!

and to the long idling zone, I never had any problem at all and I did like 240 miles distance at idle in vacation this year, stock cam, and no water reversion whatsoever!