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White steam exhaust from only one twin
|Author||Topic: White steam exhaust from only one twin|
posted 10-01-2002 07:32 PM ET (US)
I notice that when I run my engines hard (above 4500 RPM) that my starboard engine makes white 'smoke' AKA steam (it's definately steam) from the exhaust ports just above the waterline, but the port engine doesn't. Stills runs fine, but I wonder where the water is getting in? Does a two stroke outboard blow a head gasket like a car?
posted 10-01-2002 07:54 PM ET (US)
What engines do you have, Morocco?
If they normally discharge cooling water through the exhaust you may simply have one engine running hotter than the other.
If you have a head gasket problem it can be identified quickly with a compression test.
Red sky at night. . .
posted 10-01-2002 09:20 PM ET (US)
Steam means hot or water intrusion. Water intrusion is easy to detect because your sparkplugs will be CLEAN.
posted 10-01-2002 09:49 PM ET (US)
Duh! Johnson 150 GTs.
The Starboard engine does run hotter than the port, or seems to. This last time it actually smelled a little 'scorched' but I just repainted the cowls a couple of weeks ago, and this was the first extended run since then -- I only notice the steam after throttle down, right after a prolonged high speed run.
posted 10-02-2002 09:04 AM ET (US)
Start with waterpump.
posted 10-02-2002 09:18 AM ET (US)
I think it's a sign of something serious: I had an experience with a 50 hp: I got into some heavy weeds, and didn't notice my intakes were blocked. As I was running toward shore, I noticed that I was blowing steam - a fair amount. I immediately shut down, and when I removed the cowling, the engine was so hot that water drops would sizzle on the cylinder heads.
It took 1.5 hours to cool down enough to restart. I believe your water pump is failing or your intakes are partially blocked, or somehow not able to get enough water. IMHO, I'd correct it before running again. I was lucky: no permanent damage, but I'm sure my pistons were scorched a bit.
posted 10-02-2002 01:42 PM ET (US)
Morroco, if you accelerate slowly up to and past 4500 rpm, does the steam start the moment you hit 4500 or a how long after. If you decelerate under 4500 rpm how long does it take for the steam to stop, i.e. if you run at 4700 rpm and it is steaming, then drop down to 3500, does it stop right away, or after some time, if so, how long? Do you have temp gauges, if so, what do they read at all the above situations? Also, I would imagine that your engines have thermostats. Though not recommended to extensive use, you may want to pull the thermostat off that engine and run without it to see if the engine is running cooler. Do not run extensively at idle without the thermostat though as this will cause excessive fouling. If you have a test basin, check the thermostat for proper operation. Remember that when you run at or near WOT, the engine gets hot fast and needs alot of water to cool, it is best to slowly come off of WOT so that the block is not super hot and then suddenly getting little cooling due to low rpms.
posted 10-02-2002 02:57 PM ET (US)
No temp gauges, but both water pressure gauges indicate hi flow that is equal at near WOT (they say '30' whatever that relative unit is supposed to mean), and both tell tales are putting out good flow that also looks pretty equal between the two engines.
The steam doesn't happen during the high speed runs, but only when I throttle down at the end of them, then it seems to go away in a minute or so, relatively quickly.
posted 10-02-2002 03:07 PM ET (US)
Water pressure is ok so I assume you may have a thermostat sticking. All engines will let out a little steam when you do that, especially when the ocean temp drops.
posted 01-31-2003 09:39 PM ET (US)
Finally getting around to an update about this problem -- Bigshot is the winner.
Apparently one of the little rubber 'dams' inside the water jacket of the steaming motor became deformed, and sort of swelled up enough so that instead of forcing the water in a stream around each of the cylinders it somehow 'short circuited' the water flow so that only one of the cylinders was being cooled. The engine heated up enought to blow the head gasket and allow water to intrude into the block.
Now get this -- the little overheat alarm horns were mounted under the floor, forward in the cuddy cabin, so even though the horn worked, I never heard it, not a chance.
Anyway, it gets better. I always had water flow out the tell-tale and good pressure on the gauge because there is apparently no relationship to either of those indicators and the fact that water is reaching the INTERIOR of the engine. And what about the SLOW circuit? My engines were the built the year before those were installed.
So, the result was two new cylinders, all new gaskets, and a rebuilt crank as well as the replacement of all those little rubber thingies in both engines. We moved the horns to the area just to the right of the helm, under the shelf to the right of the throttles.
Is there a moral to all of this? I guess so -- check the horns by grounding them once in a while. If I'd done this, I would have realized that they were in a terrible place (you could hardly hear them when the engines were OFF)
The whole engine cost a LOT of money to rebuild, all because of a little rubber part.
posted 02-04-2003 06:39 PM ET (US)
You should install cylinder head temp gauges.
They are a necessary compliment to the water pressure gauge. Now I know why they come standard on Mercs, as with the alarm horns in the ignition harness, only one foot from the ignition key, which sound every time you start the engine. This lets you know they are working.
I think steam in the exhaust flow is always an indicator of a blown head gasket or O-ring.
posted 02-07-2003 02:35 AM ET (US)
Yeah, my hindsight is perfect, now with these new, expensive glasses.
I think I'll probably install the CHT gauges at some point, although the consensis around here among the gear heads is that the horn always sounds before the indicator reading rises (which doesn't make much sense to me -- the horns go off at 203 degrees according to the manuals, and I'd be surprised at much 'lag time' for the gauge to show the same).
But the odder thing, to me, is that the horns DON'T sound when the power comes on -- as far as I know, the only way to test them is to ground the tan wire at the engine. The mechanic (who is one of the most respected, experienced outboard guys in the Los Angeles area, and has worked on the boat since it was brand new) says the horns NEVER did that test tone. But I'd sure like to figure out a way to set it up to do that.
I wonder if I got newer Johnson ignition switches, would I be able to rig that.
Does anyone know if 150s have a place to put the CHT sensor on the heads, or do they have to be drilled/tapped specially?
LHG -- I thought the same about steam from my experience with autos/head gaskets, but with the good water pressure, flow and lack of both horn warning and SLOW circuit, (which it turns out, contrary to the previous owner's belief, was not on this engine) I was able to 'disbelieve' my own eyes.
posted 02-07-2003 03:04 PM ET (US)
Iím not sure if the 150 has a pre-tapped thread in the water jacket or not. However, I just bought two Teleflex Premier Temperature gauges for my Johnson V4, one for each cylinder bank. I bought the Teleflex outboard gauge kit which comes with a sending unit that can be threaded into the water jacket. The kit also contains a sensor bracket, if you do not have a pre-tapped water jacket. The bracket can be used by removing a head bolt and reinstalling the bolt so it supports the bracket. The temperature sensor screws into the bracket and makes contact with the head. So using the head bolt as a heat sink and pressing the bottom of the sensor into the head it should get a pretty accrruete reading, without tapping into the water jacket.
I hate to tell you this, but Overtons.com had an inventory clearance sale last week. I bought these gauge kits for $10.00 a piece. I do not know if they are still selling them at that price or not.
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