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TheAutoBuilder
HTM On The Water
Deck/Running the Paul Pfaff-Powered Cat
Author
Bob Carpenter
WORDS AND PHOTOGRAPHY
We chronicled the building of the Challenger 600 EFI engine over the course of two months and now the boat is ready to get out on the water for testing. We headed out to Lake Elsinore in Southern California (one of the few lakes without a speed limit) and gave the boat a whirl. With the help of Paul Pfaff Racing Engine’s Gordon Jennings we had a good day on the water.
Gordon hooked up his laptop computer to the EFI engine and proceeded with the tune-up. Compared to a carbureted engine the EFI is a breeze to adjust. A few keystrokes here and there and the fuel curve is adjusted, the idle speed is tweaked, and the engine is ready to go.
With everything tuned we were able to hit 77 mph at 5700 rpm and then watch the boat idle at a very conservative 800 rpm. Our best 0-30 mph time was 8.9 seconds. We pushed the HTM from 0-40 in 10.8 seconds and managed to go from 0-50 mph in 12.7 seconds. Going from 0-60 mph was accomplished in a thrilling 14.9 seconds. The throttle response on the boat is extremely quick and acceleration is more than impressive. Grab a handful of throttle and you will be forced back into the seat, that’s for sure. Cruising speeds are efficient with 43 mph being seen at 3500 rpm and 55 mph achieved at 4500 rpm.
Rest assured, we will continue to test the HTM and see how much more we can get out of it. Stay tuned.
1. Getting the HTM back on the water with a new powerplant was an exciting day. 2. After installing the Paul Pfaff Racing Engines Challenger 600 EFI engine into our 24-foot HTM cat the boat was taken to the lake for an initial test. 3. Who’s that backing our HTM test boat back into the water at Lake Elsinore? It’s none other than Fred Inman, Sr. of IMCO fame. He just happened to be at the lake doing a little testing and helped us out. 4. After getting the boat on the water a quick hook-up was required. 5. Test equipment was hooked up to the engine prior to running it. 6. With a modern EFI engine the tune-up is conducted with a laptop computer. 7. Gordon Jennings of Paul Pfaff Racing Engines warms up the engine and checks the idle rpm. 8. Gordon drives the boat and tunes it at the same time. He’s a multi-talented guy. 9. After initial tests it was determined that a different prop would be best. 10. A 22-inch four-blade prop was installed on the BMax drive. 11. After switching hubs, the Mercury prop nut was screwed on. 12. The nut was tightened and the boat was ready to go back into the water. 13. The Challenger 600 engine from Paul Pfaff Racing Engines is both a looker and a runner. 14. After all was tuned, the boat accelerated extra hard and tapped out at 77 mph at 5700 rpm. Executive Editor Bob Carpenter takes his turn at the helm.