UPDATES :  05-28-00
UPDATES :  01-15-01
 

The tanks are mounted along each side of the engine. They can be moved either to the front or the back to fine tune the boat balance. The tanks are Sullivan seamless 2 oz  oval and are in series. Because the tanks are along side the center of gravity balance problems are not noticeable.  As the tanks empty the boat will tend to catch more air aditional, weigth may need to be added. The battery pack is mounted in the  nose of the boat to keep the balance of 1" back of the trailing edge of the sponsons. The engine uses the stock flyweel and an octura flex-hex coupler. Running harware is mostly from octura including a .120 step down 1/8 prop shaft. A leaky carburator kept me from performing further setup.  NEW 05-28-00 I took the engine apart to see if I could find why it kept on stalling whenever I applied full throttle. I took the carburator apart and cleaned it out with WD40. I then changed all the O-rings on all the needles and put it back together. After this carb. rebuild everything seemed to work perfectly. The engine  was running well and it was reacting as expected from carb. and water cooling tuning . Now I could do some real testing. On the Pond:  The boat was running strong. but on a quick sharp turn the rudder got bent badly. I had used some thin alumium for the rudder and it appeared not be strong enough. I made another rudder out of 1/16 al. sheet. It seemed to work better than the other longer one. The boat was more stable and not as darty as it was with the other rudder. I continued to test the boat to try to find the right setup. On chopy water the sponson would rise up and the boat would blow out of the water. The rear seemed to be too low and it was causing the boat to have too much positive angle of attack. The tunnel was getting too much air. On smooth water the boat would run well. Eye-speed was in the mid 30's. I knew that the design could reach well into the mid 40's, but the setup had to be just right.  I tried 4 different props. 1.Octura  X432 the boat had good speed excellent turning. I increased negative strut angle and the boat had a more neutral attack angle. The blow over problem seemed to go away. 2. The 1732 Lifting prop didn't seem to increase performance much, the boat hopped on the corners. I didn't re-adjust the strut angle to account for the lifting from the prop. I will test more with this prop. The Y535 was faster than the X432 but the boat lost some speed on the corners. I think an X435 should fit nicely. 3. The boat "seemed" to run faster with the 1735 it had a mean rooster tail and it was going plenty fast. There was just a hint of hopping in the corners, but if I reduce some of the strut negative angle I should be right on the ballpark. I think it depends on the water conditions. I'll focus on using the Y535, X435 and 1735 now because the engine seemed to pull the props with no hint of increased head temperatures. The launch is a little harder, but a little more throttle is all it took.

 
NEW 01-15-01

Performance Update:

Well, after a long and hard battle with the .120 3/16 flex-shaft, I’m finally back. I must have had a dozen flex-shaft failures since last spring. I was ready to give up on this boat! An experienced boater took pity on me and told me how to fix it. Well, $10.00 later I had 50% silver solder. This stuff would still melt at lower temperatures of 1000F but it had a high tensile strength.  I made two(2) shafts for the boat, not really knowing if they would work.  I got the boat out with the new TRX-TURBO modified engine and a Prather stainless S210 prop. Normally this is the prop used on stock .21 outboards so I knew it would place a high level of stress on my drive train. I had just recently upgraded all the hardware and installed some added bracing on the strut and rudder assemblies. The beefed up hardware added weight to the boat, but it looked like it needed it.

On the Pond:

Got the engine fired up and prepared to launch it. Would the flex-shaft break again? I had been through many a hair pulling session, I also remembered I had left my casting reel at home – It was going to be a long day. Well thing didn’t turn out to bad. The engine was a little lean and it hesitated when I gave it full throttle. It took me a couple of runs and about 5 minutes of run-time to get things squared away in the tuning department. After that it was smooth flying… and did it fly. With the other TRX .12 stock engine the boat would slow down in the corners and it would take it a couple of seconds to get back to top speed. With the TURBO I had power on demand. It was like the engine wasn’t even sweating it. I could of cut down on the water and probably lean it out a bit more. This thing is flying! The S210 prop didn’t really have a good rooster, which meant that I wasn’t using power to throw water in the air. On the next run I tried the huge monster Prather S220 prop. Bare in mind this is a .15 small block engine. On the next run the boat pulled the S220 with authority all arround the make-shift coarse. In the conrners, on the straigth-a-way. The boat worked perfectly.

Hull tuning:

I really haven’t made a lot of changes in the trim area since last time. After adding the ¼ to the rear ski I was able to flatten the strut angle by a large degree. This prevented the rear end from hopping in the straightaway and now the boat is actually very well mannered. The S220 adds a lot of stability to the boat when compared to the Y535 that I had been using before. No doubt that the larger prop is putting more pressure on the front end. The pond was not very choppy during today’s testing but there was a good tail wind that allowed me to nail the throttle with little concerns of blowing over. The day’s only blow over occurred with the boat turning away from me with the wind head on. I really couldn’t tell from my angle that the boat was getting out of shape.

Lesson of the Day:

Well, this was really the first good run with the new TURBO motor. I had done all the testing except one –I didn’t know how much the fuel would last with this highly modified engine… Well I had enough fuel for about 10 minutes of hard running. Unfortunately the boat didn’t give me much of a sign. As soon as I noticed the engine slowing down it was too late. No reel -No tennis ball and the boat was in the middle of the pond. To make things even worst the wind was dying off. Lucky for me the pond is in an industrial park with a beautiful paved walkway that goes around the bean shaped course. I decided to take a walk with my Son Enrique. When we got back the boat was making its way back to shore. A few minutes latter I retrieved it by hand. What an awesome day!