Teague On Tech: Q & A with Bob Teague July 2022

Speedboat July Issue

As seen in Speedboat Magazine’s
JULY 2022 Issue.

29 FEVER Props

Dear Bob:

Q. I have a 2004 29′ Fountain Fever with twin 377 Mercury Racing Blue Scorpion engines. I am currently running Bravo 1 propellers that I had “lab finished.” The result is that I now have too much prop slip. At the peak rpm of 5,200, my boat can achieve 79 mph. I was considering the Bravo 1 FS 32″ pitch propeller. Is that a good option?

Justin Moscato
Minooka, IL

The Mercury Racing Lab Finished Bravo 1 props are best at full speed and not as efficient in the midrange speeds. Many times, if you take a pair of stock propellers and have them “lab finished” by a shop that is less than qualified, you end up with propellers that are not as good as they were before they were modified. Your efficiency is not great at about 18-percent slip. A more realistic slip percentage for your boat would be between 12 and 14 percent. If you were running stock Bravo 1 propellers with a slip percentage of 14 percent, you boat would be going about 84 mph at 5,200 rpm.

Above: Mercury Racing Max5 and Bravo 1 propellers.

The Mercury Racing Bravo 1 FS props are slightly lab finished and have some diffuser removed to help the outboard applications achieve higher rpm to get on plane. This might be an advantage for you with the lower torque available with the small block engines. It would be interesting to know how a pair of stock Bravo 1 props worked to get a comparison. The Bravo 1 FS propellers are gaining popularity for many stern drive applications. They are also available in odd and even numbered pitches. This would give you the ability to go to a 31″ or 32″ pitch. Based on the information you have provided, I would select the pitch that results in the best overall performance. If you are only interested in top speed, then selecting a 32″ pitch Bravo FS 1 or might be the way to go but you might sacrifice midrange acceleration and increase the time to get on plane. I think a good compromise would be the Bravo 1 FS 31″ pitch.

The Mercury Racing full lab-finished propellers would likely result in the maximum top speed. They are available in “Pro Finish” which are precision media polished, or hand finished satin for an extra charge.

If mid-range efficiency and lower rpm at cruise speeds is your goal, your boat might also work well with the Max5 propellers, but I think you would need to go down in pitch to a 28″ or 29″.

HOT OIL Problems

Dear Bob:

Q. I have a non-marinized Chevy Gen VI ZZ-502 in a Sanger Mini Daycruiser. It has a 10-quart oil pan. The engine water temperature stays right at 160 degrees all the time. On long runs, I’ve had the oil temperature reach 280 degrees so I’m thinking an oil cooler is needed. I’m also under the impression it’s wise to have the oil reach a temp of 212 degrees to burn off moisture, etc. My plan is to use a remote mounted oil cooler I have and use the drilled and tapped oil passages adjacent to the filter pad to run lines to and from the cooler.

Do you think I need to include an oil thermostat in the system? What do I need to do regarding the two bypass valves located on the block near the filter pad?

Kurt Kuester
Meridian, ID

Remote oil cooler adapter kit (top) and
Generation V block oil passage block-off.

You definitely need an oil cooler in your boat. Being that your engine was not designed for marine use, you should try to keep it running on the cooler side as opposed to warmer. Accordingly, it is probably not necessary to include an oil thermostat unless you are somehow getting water in your oil. If so, that problem should be addressed separately which normally indicates an issue with the cam profile in combination with an exhaust system that has the tendency to revert exhaust water. Without the thermostat, if you let the engine warm up properly before you run it hard, you should be fine.

Do not use the factory oil cooler ports that are located in the block. These are for use in automotive and truck applications and require the installation of two check valves. Both of the check valves are located in the filter location. One is visible in the flat area under the filter and the other in in the center under the screw-in adapter. These bypass valves are designed to let oil by if the filter is clogged and will route unfiltered oil back to the engine. They need to be removed and a plug placed in the one in the filter pad. We use a press-in aluminum plug that we make. Mercury Racing also uses something similar. Then, a remote filter adapter must be used to connect the oil line that routes the oil through the cooler and filter in series. This way, all of the oil must pass through the filter and cooler.

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