Too much Exhaust steam?

[shawzy44]

Hi everyone.

I wondered if the amount of vapor my F-28 is blowing is cause for concern?

At normal cruise (1800-2200RPM) the vapor is not really visible, when we get up on plane and push it a little bit (3500RPM) the boat really pushes out a lot of vapor.

Engine details: Rebuilt in 1996, good compression and timing, new plugs, wires and caps are still good. Tuned up 3 days before this video was taken. New water impellers at the start of the season.


My temp gauges and sending units have been replaced but they don't seem to be working correctly as they read 120F... which seems WAY too low from the norm 160F running temp. (This is an on going repair issue).

Anyone with 318's pr better yet an F28 w/ 318's see this much action out of the exhaust at 3800 RPM??

Video:
1800RPM:
http://gallery.me.com/kevin_d_shaw#1000 ... olor=black

3500RPM: http://gallery.me.com/kevin_d_shaw#1000 ... olor=black

Interested in the Forums' thoughts on the last video.

Thanks,

[TADTOOMUCH]

I have twin Chrysler M360's in my F-32 and the engines are raw water cooled. Not sure if yours are raw water or fresh water cooled or not. The thermostat for each is different. Raw water cooled usually is 140 degree thermostat and the fresh water cooled is higher near 160 degrees.

My temps rarely get above 135 on the gauges in Lake Michigan with lake temps near 72 at full throttle and I produce a fair amount of steam at that speed but the steam seen is a function of outside air temperature too.

With new senders and gauges I would think you are reading correctly but your thermostat might be either the wrong type or malfunctioning. Do you see any deflection in the gauge or is it stuck at the lowest indication of 120?

[prowlersfish]

Do both engines have about the same amount of steam ? What was the outside temp at the time ?

[Capt. Z]

Shawzy44, My 76 F28 is fresh water cooled and run about 150 to 155 degrees with the current surface water temp at 70 degrees. (318s btw)

Sunday morning we left the slip at 5 am to head out fishing. The air temp was a cool 44 degrees. I was leaving with a pack of boats that had no business being out there. I came through the Superior entrance & dropped the hammers to leave the tin can brigade behind. At 4100 rpms I had a vapor trail behind me a mile long. These cooler early fall days with warmer water temps will make steam especially at high rpms.

120 degrees is low to be a operating temp, if that is the true reading?? What was the lake water temp vs the air temp in your videos? Its odd that both motors show 120? I would change out the sending units. I also would make sure I was getting a true temp reading that may tell the story on the steam?

[TADTOOMUCH]

Both engines produce the same amount of steam. I see more steam when the outside air temperature is lower but I can see a fair amount of steam while at cruising speeds of 20 to 25 knots at 80 degrees outside air temperatures all in Farenheit scale.

Go to this site for gauge trouble shooting.

http://www.cruisersforum.com/forums/f14 ... g-645.html

It will let you test if the sender or gauge is working properly. My guess is that you are fine if you have water coming out of your exhaust at a good rate and if you can touch the top of the exhaust manifolds and they are not extremely hot.

Your engine will run hotter than the water coming out of the exhaust. There are two water pumps on raw water cooled engines. One sucks water out of the lake and pumps it to the engine and through a bypass into the exhaust. The other pump circulates water through the engine just like a car and then exhausts out with the other water. When the engine gets above 140 degrees the thermostat opens up and lets more water from the lake into the system to keep it from overheating. Fresh water cooled engines have the same pump to suck water out of the lake but have antifreeze filled cooling system with a heat exchanger similar to a car but instead of a radiator they have a heat exchanger so the antifreeze can exchange heat with the lake water. If you have a fresh water cooled system they run hotter like 155 to 165 degrees as far as what the temperature sensor sees.

If you put new sensors in make sure they are for your brand of gauge and also if they are single or dual station sensors. If you have two helms you need a dual sensor unit.

[TADTOOMUCH]

If you put a single station sensing unit for temperature in your dual station boat, it won't move much until the temperature gets very hot.

You can check the to see if you have a dual or single unit with a resistance meter. It should read 300 to 400 ohms from the connector point to ground if it is a dual station sensor at room temperature and 600 to 800 if it is a single station sensor.

This may be why your gauge is not moving much but from your video it looks fairly normal.

You could also disconnect the sensor wire from either the upper or lower helm and see if the gauge moves more after that is done once if warms up. that would tell you if you have the wrong type sensor unit.

[shawzy44]

Thanks for all the comments.

The video was filmed on the weekend - outside temp 80F water temp 78F.

The steam is similar in volume from both sides, so I guess all is good.

I suspect I have the single sensor/senders and not dual -I'll look into this further on the weekend.

[ready123]

Looks OK.. here is what I got last year slightly lower rpm, temps likely similar.
http://www.flickr.com/photos/79664671@N ... 4286680574

[rossjo]

Didn't get any videos, but I'd check the heat exchanger and block temps with a IR gun (< $75) after both engines warm up and see if you have some hot spots. I wouldn't expect the block (around the heads) to be over 190deg, or the heat exchangers to be over 250deg, except the exhaust manifold might be hotter right at the head.

Anyone else with better numbers to use, please chime in ...

A friend had a new Luhrs 36 with twin 502 Mercs in it. It was slow, so we'd leave the dock at 4am to get to the ledge around day break. There was so much steam you couldn't see behind the boat most mornings - and you would be soaked if you sat on the transom for the ride. Boat is gone now - burned 300-350 gallons of gas to get to the ledge and back in a day.