To me the motor doesn't sound right. I would go back to basics and make sure you are firing on all eight and do a leak down to make sure your not holding a valve open. In my opinion your cam should not be reverting with that exhaust setup.

Bingo, just listened to the video, it doesn't sound right, sounds flat and lazy, firing order off, valve lash

An exhaust leak at the head or elbow can mess up your world too.....

I have done a leak down as well as compression test. all cylinders within a 7 psi window. all plugs look the same, burning a bit rich at idle.

its all jacketed up to the end. the last elbow is my current standard height elbow simply turned 90 degrees. the main elbow with curved extension is two of my +6" elbows cut apart and welded back together

I did not draw the nipples yet, as most will be left in their current position on the elbows / pipes. as I have to cut the existing welds and do some sectioning prior to welding together


https://forums.iboats.com/filedata/f...8&d=1516492126
https://forums.iboats.com/filedata/f...otoid=10534891

Absolutely. When I put O2 bungs on my headers I ran them without a cap and water was squirting everywhere. I put the cap back on and pulled it off after running and it was dry as a bone and sooty. An exhaust leak can wreak havoc.

I agree with Kvogt and F2, I'd be going back and looking at the valvetrain after hearing you rev it at :35 seconds here...and if you have water pizzing out of that flange as the video shows, I wouldnt rule out a leaking manifold or tailpipe weld.

I have already pressure tested the manifold and tail pipe. they held 15 psi for over an hour prior to me looking into reversion

the water coming out the joint is what was being pulled back into the cylinder and pooling in the maifold. also note in the video above, I idled the motor down to 650 RPM and the motor is sitting at 5 degrees tilted forward. I am back up to 950 currently and it doesnt mater where the motor sits as it still pulls water vapor back up.

it does it with brand new (never run before) +6" elbows too

sealing the flange gaskets with permatex #3 took care of the water leaking from the joint, however still did nothing for the inside of the pipe getting wet as the water was pulled back in. still have water with the +6" manifolds. not a lot, however still have it being drawn into the exhaust

If i put a rubber sheet over the end of the elbow so the water is deflected away from the inner pipe, i can run it for 20 minutes without water in the pipe.

Yeah, when the engine is in the boat at idle and it will be 3 to 5 degrees leaning to the back, pointing the pipes furthur down.

I had a similar problem when I ran mine on stands. Be VERY careful with the hose/water pressure. Its getting way more water then when its at rest pulling it up through the pickup.

Moisture is different than reversion. Do you have standing water or moisture? Most of these cams still revert a little moisture. For example, O2 sensors dont last long and calcify from moisture. There is an article on here somewhere on OSO that discusses Moisture vs Reversion. For that reason, you have to get the engine good and hot up to temperature to truly validate.

Agreed on the angle, however doesnt seem to matter if the motor is 10 degrees backwards, flat, or straight up.

it is pooling water in the bottom of the manifold with the motor at temperature. you can see each exhaust pulse at idle and each reversion wave between the pulses. Will fire up the go-pro again, will post a slowed down video this weekend. you can see each cylinder fire, then draw back.

it could be the 114 degree LSA with the carb as most cams for carbs are closer to 110 or 112

I hear something tapping pretty hard on the rev up, sounds like a rocker