hoping one of you guys has an idea, my 73 Tahiti with a 455 has steam out the exhaust both sides, first only under load, now at 1000 rpm and up no load, oil is clean, has to be the exhaust but I can't see both manifolds failing at the same time. what do you think?

they are logs with through transom snails and the steam is not what is considered normal. its very heavy smoke-steam under load and steady smoke-steam over 1000rpm

What does your water temperature gauge tell you?

Sounds normal, if you were driving the boat on a very cold, or very humid day, the steam amounts will increase.

i even get steam from time to time on my exhaust in the right wind/temp.  the worst is when its blowing over the back and gets everyone wet... and i have a shitton of water going thru it.

If logs even get too warm. .. something is restricted.

from my phone

Logs get clogged easy.  I run in pretty shallow water and always suck sand and pebbles.  I installed shut off valves on block so i can drain water and debris every trip.  I always remove the hoses that go from thermostat los and run water backwards the sand and crap will pour out the back. My log system never created pressure like ot headers do.

from my phone

Good point....my beer goggles keep me tracking in one direction. Check all the possible factors first!

from my phone

Are we talking smoke-screen amounts of steam?  How do the spark plugs look?  If they look new, you have a little water-injection action going on with some water sneaking back in through the exhaust valve.

Honestly, I have moved beyond logs a long time ago and never looked back.  I run through-transom headers with every drop of water that goes through the engine dumping into the headers.  There is a little steam while underway and I don’t notice any steam while idling.

As far as smoke, I run mechanical injection that is tuned a bit fat at idle.  I don’t see any smoke at idle, but its presence is apparent from the sooting on the transom and swim steps.  While underway, I don’t see clouds of billowing smoke pissing off the environmentalists, but there is some caught in the turbulent air trapped between the transom and wake.  Though I don’t see huge clouds of smoke, I do know that it is tuned a bit on the rich side to prevent lean-out.

Idling 5-10 seconds with no load or even a quick rap of the throttle may not be enough to get a mechanical problem to rear its ugly head.  While idling on a trailer or in a marina, you will probably never see any issue until you get out on open water and under load.  It is hard to diagnose online with limited information.  I don’t really see too much water through the exhaust being the cause of too much steam.  I have seen water pouring out of the exhaust in situations like mine where all water exits the exhaust, just not in the form of excessive steam.  I believe that your exhaust dumps under water until speed increases.  Again, I don’t see a bunch of steam/smoke here as the water will actually filter out particulates and condense steam.  Your old carb was “temperamental”, if it went lean under load, it could have overheated the logs and caused cracks in both sides at the same time.  I don’t see cracks in the logs causing excessive steam, especially if you are not getting reversion.

The reason I ask about a mechanical problem is because once-upon-a-time, my baby’s momma bought (against my wishes) a ’92 Lumina.  Under normal driving conditions, it ran great.  During WOT acceleration (passing) it would blow a huge smoke-screen.  I was so over that car by then that I didn’t even want to try to look into the cause, but I think that high-RPM caused the rings to flutter and lose seal and oil control.  Shortly after, sis and bro-in-law blew it up and I didn’t have to look at that POS any longer.

I am sorry brotherman, if it is not a mechanical issue, I am stumped.