Stu

Oct 122014
 

If you know me or my blog, you know I watch Lake Powell. Most of my posts are about the water level increase expected each spring and early summer. But many boaters have reported weather problems at the lake that weren’t related to dust storms, thunderstorms or wind storms. Triple digit temperatures are a common occurrence on Lake Powell. The high temperatures can cause engine problems.

Waterskiing at Lake Powell

Waterskiing at Lake Powell

On of the intended benefits of fuel injection was to prevent vapor lock. The gut reaction of most “gear-heads” and marine mechanics is that a fuel injected engine can not suffer vapor lock. I’m now a believer that there is a mechanism for vapor lock in a marine engine.

Marine engines run in a tough environment. The stern drive motors are typically inside a small engine compartment with limited ventilation and exceptional noise insulation. It’s a great environment for containing heat. The lower unit of the stern drive takes up fresh water and pumps it to the engine and support systems. It’s a great way to cool a motor while it’s running. But when you shut down a boat’s engine, there isn’t a natural heat release path. You can run the engine compartment bilge blowers to provide air flow. But there is no radiator like in a car. In the Lake Powell’s summer temperatures, blowing 110 degree air over a 155 degree engine has little effect.

To protect the fuel, a fuel cooler is a part of the cooling system. The fuel cooler’s intent is prevention of fuel vaporization due to high engine compartment temperatures. The water comes in from the outdrive, flows through the power steering cooler, then the fuel cooler, before going to the engine’s thermostat housing. This doesn’t work after the engine is shutdown, either.

Over the last few years our boat driving habits at the lake have changed. We used to spend lots of time on the beach with brief runs for water-skiing or wake boarding, or sightseeing. Now, we tend to do longer runs with plenty of canyon exploring and trips to Rainbow Bridge with friends. This means we run our engine longer and the compartment and engine gets thoroughly hot. Here is a temperature profile of the engine during a summer weekend trip. I measured the temperature on the top of the thermostat housing lifting eye. So, it wasn’t in direct contact with the housing or engine.

Engine compartment temperature profile, July 18-19, 2014.

Engine compartment temperature profile, July 18-19, 2014.

The heat build up is fairly quick. Idling the engine after a run provides a fair amount of cooling. But after shutting down the engine, the cool-down is much slower. Opening the engine hatch provides a better cool down of the top of the engine. Shorter runs result in a much faster cool down. We had to open the hatch because the engine wouldn’t start; we hypothesized vapor lock. But the engine compartment temperature had cooled much at this point. Shouldn’t it have started?

There is a theory about some marine engines. The theory is that some of the engine cooling water flows backwards after engine shutdown. This takes very hot water out of the engine and back the way it came. The first stop on the way out is the fuel cooler.

My son and I tried to replicate the outcome. We took our boat on a long, roughly 40 mile round trip. We went straight back to our slip at Wahweap Marina and shut down the engine as quick as possible. We watched the temperature on top of the thermostat housing lifting eye, and the air temperature inside the fuel cooler box, just an inch or so away from the real heat exchanger.

Thermostat housing and fuel cooler temperature

We watched the fuel cooler temperature quickly move from 101.5 degrees F to 121F at 15 minutes, and hit a top temperature of 124F by 30 minutes. At 45 minutes, we thought the temperature had stabilized and attempted to start the engine. It turned over, but didn’t start. We took a video the fuel being injected at the throttle body when cool, and again when it failed to start.


The fuel spray in the hot video is quite different with spurts, drips and gaps in the flow. The cool fuel spray is well atomized. What a difference!

On other trips, I tried to measure the temperature of the cooling hose that allows back-flow to the fuel cooler. Since the data logger I used had a self-protection turn off at 140F degrees, it only produced a few minutes of data as the temperatures climbed above 140F. Back-flow was the likely issue.

Mercruiser is the manufacturer of my engine. They have provided a tech bulletin about this vapor locking issue on their V-8 engines.

Mercruiser Vapor Lock Tech Bulletin

One of the solutions Mercruiser gives is to insert a check valve in the cooling system to prevent back-flow. I opted for this option. I installed the check valve in the cooling line between the fuel cooler and the thermostat housing. When I removed the existing hose, I found that it was mostly empty. To me, this validated the back flow problem as an issue. The top part of the engine coolant drained out via the fuel cooler. With the included instructions, the valve was remarkably easy to install. An experienced mechanic could do it in probably five minutes. I invested 45 minutes. Here’s a picture of the installed valve.

Cooling line check valve installed. Blue with yellow in the lower right.

Cooling line check valve installed. Blue with yellow in the lower right.

To test the repair, we did a high-speed run to Rainbow Bridge. When we shut down the engine, I watched the fuel cooler temperature. At 15 minutes, the temperature had dropped by 0.3 degrees. In other trips since then, it has occasionally increased, but never above 103F.

Every pump has a low pressure intake, and high pressure discharge. The fuel pump takes it suction on the outlet of the fuel cooler. The pump’s suction can vaporize the heated fuel, even if it is below boiling point. I wanted to record this some place because many boaters at Lake Powell to get hit by this phenomena.

 Posted by at 6:35 pm
Oct 062014
 

The remnants of Hurricane Simon are on their way to Arizona. The big question is still around which path he will take. The Navy NoGAPs computer model has the bulk of the storm going to the west and north of Flagstaff. The GFS model has the storm going to the south and east of Flagstaff. Which way will he go?

You can see the subtle differences in the two models below. The National Weather Service’s chances of rain peak at 50% right. Wunderground peaks at 80%. Accuweather is forecasting rain and thunderstorms. I think we are going to get wet. I think we need to keep an eye on this storm because it can bring heavy rain and flooding…again.

6 hour precipitation outlook at 48 hours from the US Navy's NoGaps model.

6 hour precipitation outlook at 48 hours from the US Navy’s NoGAPs model.

6 hour precipitation outlook at 48 hours from the National Weather Service's GFS model.

6 hour precipitation outlook at 48 hours from the National Weather Service’s GFS model.

 Posted by at 5:27 pm
Oct 042014
 

Something new for my blog readers. I’m going to occasionally add reviews for product that are weather related to my blog. First up is the new WR-299 Weather Radio. Please watch the video for details.

This is a great compact emergency weather radio that offers AM/FM and Weather bands. It also have an Alert Mode to let you know when severe weather is on the way. The WR-299 has multiple power options:

*Solar Charger
*Hand Crank Charger
*USB Charger
*AAA batteries

It can also be used to charge your iPhone or other smart device. The speaker is clean and crisp. I can’t believe how good the sound is coming out for such an inexpensive radio.

The flash light is bright and will easily guide you through the dark.

This is an excellent addition to my Lake Powell kit.

 Posted by at 2:19 pm
Sep 302014
 

I’ve struggled the last few days with a broken internet connection, malfunctioning iPhone and a rainy weekend. The weekend struggle was the wonderful malaise that can hit Arizonans when it rains all day. Nonetheless, the Climate Prediction Center issued new outlooks for October and the 3-month period October to December.

The outlooks point to El Nino developing. I’m still not sure this is a reasonable expectation. Last spring and early summer, the sea surface temperatures in the Pacific Ocean near the equator appeared headed for a strong El Nino. Unfortunately, the trade-winds did not shift to support it and the sea surface temperatures fell. There is another burst of warm water headed towards Peru now. If the winds shift, we will have El Nino conditions and a high likelihood of a wet winter. If they don’t shift, we will see La Nada neutral conditions(I think this is what will happen). Here is NOAA’s narrative about the outlooks:

CURRENT ATMOSPHERIC AND OCEANIC OBSERVATIONS ARE CONSISTENT WITH ENSO-NEUTRAL 
CONDITIONS WITH THE LIKELY TRANSITION TO EL NINO CONDITIONS IN AUTUMN AND 
WINTER. A WEAK EL NINO EVENT IS MOST PROBABLE, HOWEVER THERE IS A CHANCE OF 
EITHER A MODERATE EVENT OR CONTINUED ENSO-NEUTRAL CONDITIONS INTO WINTER. A 
STRONG EL NINO EVENT IS NOT LIKELY TO OCCUR THIS YEAR. MOST DYNAMICAL AND 
STATISTICAL MODEL FORECASTS OF EAST-CENTRAL EQUATORIAL PACIFIC SEA SURFACE 
TEMPERATURES (SSTS) IN THE NINO 3.4 REGION (170W TO 120W LONGITUDE AND 5S TO 5N 
LATITUDE) INDICATE A WEAK EL NINO (+0.5C TO +0.9C) WITH PEAK ANOMALIES IN THE 
EARLY WINTER.

 

Here are the outlooks:

One-month precipitation outlook for October 2014 from the Climate Prediction Center

One-month precipitation outlook for October 2014 from the Climate Prediction Center

Three-month precipitation outlook for October- December 2014  from the Climate Predicction Center.

Three-month precipitation outlook for October- December 2014 from the Climate Prediction Center.

 Posted by at 7:10 am
Sep 272014
 

A strong cold front is crossing Arizona from west to east today. While the moisture is coming from the south, the cold front is a winter weather phenomenon for Arizona. We are expecting fast-moving thunderstorms with heavy rain and other severe weather. This is reminiscent of the storms on October 6, 2010.

The National Weather Service isn’t taking any chances. They have posted severe weather watches and warnings. Check their website for updates.

 

Weather Story from the National Weather Service (Septemer 27, 2014)

Weather Story from the National Weather Service (Septemer 27, 2014)

 Posted by at 7:02 am
Sep 162014
 

I have zoomed in and cropped the image below. There is still a pronounced boundary to the heavy precipitation area. The precipitation scale is the same as in the earlier image in my last post. This is from a shorter range, high-resolution model. I think Flagstaff ends up in the 3/4 to 1 inch range. Notice that another boundary is forming along I-40 to the east. Stay tuned! There will be areas of Arizona receiving large amounts of precipitation over the next few days.

Cropped 72-hour total precipitation forecast from the North American Mesoscale computer model by the National Centers for Environmental Prediction. 16 September, 2014.

Cropped 72-hour total precipitation forecast from the North American Mesoscale computer model by the National Centers for Environmental Prediction. 16 September, 2014.

 Posted by at 6:49 am
Sep 152014
 

Watching the GFS animation for the next 7 days this morning, I noticed a curious flow in the precipitation pattern. This flow reminded me of our last interaction with the remnants of a hurricane. Hurricane Norbert’s moisture missed us by traveling barely south of us. Next up for us are the remnants of Hurricane Odile. Currently, Odile is hitting Baja Mexico. Model predictions call for Odile’s moisture to move across most of Arizona. But, this morning’s GFS model for NOAA shows that a thin line might separate seriously wet areas from damp areas. We will have to keep watching to see where the water goes.

In the image below, I have added a yellow arrow to show the movement of precipitation. There is a large difference in the amounts to the southeast of the line and to the northwest of the line.

5-day total precipitation from the GFS model. Yellow arrow added for emphasis.

5-day total precipitation from the GFS model. Yellow arrow added for emphasis.

 Posted by at 6:34 am
Sep 112014
 

The newest 6-10 and 8-14 day precipitation outlooks show wet conditions continuing. We should be dry today and Friday. There is a chance for showers over the weekend and into early next week. Sometime in the second half of next week, tropical storm, soon hurricane, Odile will deliver more moisture to Arizona.

8-14 day precipitation outlook form the Climate Prediction Center, September 10, 2014.

8-14 day precipitation outlook from the Climate Prediction Center, September 10, 2014.

5-day outlook for Tropical Storm Odile. From wunderground.com, September 11, 2014.

5-day outlook for Tropical Storm Odile. From wunderground.com, September 11, 2014.

 Posted by at 6:28 am
Sep 092014
 

Mother nature decided to blow the forecast away. There was a ton of moisture in Arizona’s atmosphere. Below is an image from Intellicast.com that shows an estimate of daily precipitation based on radar imagery. If you compare this image to from the National Weather Service, you can see that things didn’t turn out to forecast. The bulk of the moisture hit to the south of Flagstaff. The dry area shifted much farther to the west from the forecast in that image. Still for the summer we are way ahead on precipitation. Also, it doesn’t look like the monsoon season is quite finished, yet.

Estimated daily precipitation based on radar. From Intellicast.com.

Estimated daily precipitation based on radar. From Intellicast.com.

Weather Story from the National Weather Service in Flagstaff

Weather Story from the National Weather Service in Flagstaff

 Posted by at 6:51 am
Sep 062014
 

Norbert comes to town! 2.7 inches of possible rain for Flagstaff through Tuesday.

Hot off the presses from the National Weather Service in Flagstaff:

Weather Story from the National Weather Service in Flagstaff

Weather Story from the National Weather Service in Flagstaff

 Posted by at 1:10 pm
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