Reversion ?

[eightsecmopar]

Last year I installed Stainless Marine wet exhaust, water doesn't exit till the very end of thr pipes. Risers go through the transom and also have a very large radius up by the manifold. These are like the merc 525 set up. I had some other none related problems where I had to remove one of the heads, after I removed the intake I noticed that there looks like there is some water getting into the intake and exhaust ports. It appears only the rear cylinders are having this problem. I really never got alot of run time last year, did do alot of idling and running on the trailer. I have small Hydraulic flat tappet cams which is what was in there when I bought the boat. I did install Dart Iron Eagle heads because the heads that where on the engines were leaking. I just can't see how the water can get sucked all the way up this riser. I've talked to a few people and really can't get a definete answer on why or how this is happening. I'm not sure if I'm making more out of this than it is or not. It doesn't appear that there is any water in the cumbustion chamber, just the port areas. Head gaskets look like they are sealing well, didn't see any problems there. I'm wishing I went with the dry exhaust now but I didn't want to have to spend another $3000 on mufflers. If anyone has any ideas I would appreciate it.

[Ratickle]

DO you know the specs on your cam overlap?

[old377guy]

have your manifolds and tailpipes been tested for leaks?

[eightsecmopar]

I have the specs at work I will post tomorrow. The manifolds and risers are new.

[OBNOXUS]

. I really never got alot of run time last year, did do alot of idling and running on the trailer. :

getting water in the oil,,,,milkshake???

can get alot of condensation just running on the trailer,,,,,need to get the oil temp up to burn it off

[eightsecmopar]

No milkshake, oil looks fine. Someone told me that running on the trailer you tend to have a better chance of sucking water up because of the angle that the boat sits on the trailer.

[eightsecmopar]

107 degrees at .050 tappet lift

[MILD THUNDER]

Hey Clyde. Post up a pic of your tailpipes. Also, If you can find it, post the cam specs. Like Duration @.050, LSA. Should be 110, 112, 114. With a 110LSA angle combined with a good amount of duration, they can Revert water. If its the rear cylinders, than i'd say its coming in from the exhaust. The water gets drawn back up towards the elbow, than drains down the riser joint, where the exhaust runner goes to the back cylinders.

How low do your engines idle in gear? If your borderline reverting water, i'd try to keep them up around 750RPM in gear, that can help.

Most of merc's stock cams were ground on 114 or 115LSA. Except the HP500 cam. I believe those were 110LSA, and they had reversion issues if i recall.

[Ratickle]

How hard to pull a valve cover?

If you are milking up the valve covers the water is being pulled in thru the exhaust up the exhaust valve and in to the valve cover.

[Ratickle]

And what Joe is talking about:

The reason there is pull in the exhaust at idle; It is caused by 'cam overlap'. Cam overlap is the period of time the intake and exhaust valves are open at the same time. It creates a scavenging effect in the cylinder to help rid it of outgoing exhaust gases. This is why you cannot put wild automotive cams in marine engines. That 'whump thump whump' rough idle you hear on wild cammed engines WILL suck water in your engine at idle. The reason roller cam engines need more static line (Measurement of riser height) is because they have a longer overlap period than a flat tappet cam.

The static line numbers I've heard is 9" for flat tappet and 14" for rollers.......

[Ratickle]

Here is a link to Lightning. I use their headers on two of my boats.....

http://www.boatheaders.com/reversion.htm

[eightsecmopar]

Crane Cams Part # 134241 Grind # H-286-2
Lift: Intake @ cam 314 @ valve 534
Exhaust @ cam 325 @ valave 553 This is with 1.70 rockers which I'm using 1.8's
Cam Timing @ .050 Intake opens 6 BTDC close 40 ABDC Max Lift 107 degrees Duration 226
Exhaust opens 55 BBDC close 1 ATDC Max Lift 117 degrees Duration 236
I usally idle the engines around 850-900 rpm in gear drops down to around 800
No milkshake in the valve cover but like I said I really haven't had much run time on them in the water
Thanks appreciate the help

[ROGUE]

Really need those timing numbers at .005 or .006 to determine overlap. Heres a flat tappet with 75 degrees of overlap and although its close, real close to getting water to the valves, it doesnt make it even with the short elbow gil manifolds.

[eightsecmopar]

[Ratickle]

Need a little help here.... (A Lot, cause I don't have a clue)



What difference is there on the 1.8 rocker vs. the 1.7 rocker it is spec'd with on overlap?

[MILD THUNDER]

The 1.8 rockers will add lift, and a couple degrees of added duration. If he's at 236* on the exhaust side with 1.7 rockers, he may be 238-239* with the 1.8 rockers. Me personally, I wouldn't run the 1.8 rockers, unless you really took the time setting the valvetrain up for them. They can change the geometry, wear valve guides, etc. Imo, better off changing the cam to get the lift you want. I'm no engine builder though.

[eightsecmopar]

That's the set up that was in there when I bought the boat. MRD out of New York did the engines. I didn't get any paper work though. Previous owner ran it that way for the 10 years he owned it.

[ROGUE]

You have less overlap (67 degrees) than I do (75 degrees) with much longer risers. The 1.8 rockers wont effect the overlap much. I doubt your problem is reversion. But, there are other factors. The moisture you saw could have been condensation with cold water etc. I see that when running on the hose with real cold water and not actual conditions. Did you actually see drops or rusting? Guides can leak, even on new heads. Ive even seen some seats that were cut to deep and leaked. I wouldnt ignore it though. Perhaps getting the heads water chambers pressure tested. Intake manifold water passages are prone to leakage too. I always use a good sealer around the water ports when installing the intake manifold.

Contrary to what was said earlier, roller cams typically have less overlap as the ramps can be much steeper and dont have to open the valves so early. Engines I am working on now have much bigger roller cams and much less overlap which will make me much happier as I have no room for higher risers. I keep my idle at 850 out, which ends up 725 in gear. 950 an 800 when hot. After a hard run I let the engine cool down before I drop to full idle. Real close like I said.

I also noticed you said your risers and manifolds were new. Dont assume they are not leaking. Get them checked.

[eightsecmopar]

I'm actually thinking of dynoing the engine just to rule out the reversion theory and I would also like to see what kind of hp and torque the engine is making. I'm seeing rust in the ports after running on the trailer I looked up the riser with a flashlight and seen dropplets of water up in the riser, but I was thinking that was condensation.

[SC288]

Hey Clyde. Post up a pic of your tailpipes. Also, If you can find it, post the cam specs. Like Duration @.050, LSA. Should be 110, 112, 114. With a 110LSA angle combined with a good amount of duration, they can Revert water. If its the rear cylinders, than i'd say its coming in from the exhaust. The water gets drawn back up towards the elbow, than drains down the riser joint, where the exhaust runner goes to the back cylinders.

How low do your engines idle in gear? If your borderline reverting water, i'd try to keep them up around 750RPM in gear, that can help.

Joe you are right on with the idling....it was suggested with the HP500 and the older style short riser tailpipes that they idle no less than 1,000 in gear. If I have to idle for a long distance I just shut one engine down etc. and that allows me to run the one at 1,000 or so and not throw to big of a wake.