What's a picture worth?
06-26-2010, 01:25 PM
#1
Chris
Gold MemberThread Starter
What's a picture worth?
I am continuing to test with the new motor.
The digital GPS on my Garmin Chart Plotter said 100.2 mph.
The digital GPS on my Garmin Chart Plotter said 100.2 mph.
Last edited by CB-BLR; 06-26-2010 at 01:52 PM.
06-26-2010, 01:50 PM
#2
Chris
Gold MemberThread Starter
This was done with a 31 pitch hydromotive Q4x, and a 1 inch spacer. The motor was running a 1/4 inch smaller pulley, on 100 octane unleaded. We were at the Nordic Regatta in Havasu.
The boat was a handful over 93 mph, and was rocking from side to side as the prop torque rolled the boat to the left, and then the hull corrected itself. Definately not for the faint of heart.
Since then, I have decided to concentrate on boat handeling.
To this end, I purchased a new 1" shorter IMCO lower unit with 1.34 gears. The theory was that by using smaller pitched props, the blades would be more verticle to the water, causing less prop torque. Also, by experimenting with shorter outdrive lengths, the prop would have less leverage to roll the boat, and that the shorter lower unit would cause less drag. While working on Jim's 700 Ilmor boat, I discovered that it was the fastest with a 3" propshaft depth, and that at 2.5" , it lost speed, and would not hook up coming on plane even with a P5x. The smaller raked props also have the advantage in that they usually have lower slip numbers than their bigger brothers
I have discovered that over about 93 mph, that the four blades work better on my boat than the P5x does. The four blades have less blade area, lift the rear of the boat less, and don't have as much surface area to prop load the boat.
I removed the 1/4 inch smaller pulley, and filled the boat with 92 octane unleaded pump gas.
My first run was done using a 1/2 inch spacer (3" propshaft depth), and a 27 P5x. The boat still hooks up great on the bottom end, had a 43 mph cruise at 3000 rpm and topped out at 95.2 mph. Over about 91, the boat became a handfull to drive as it started doing the prop torque dance, rocking the boat from side to side at over 90 is no fun.
Next I installed a friends stock 28 merc prop. Cruise speed was down some to 40 mph at 3000 rpm, and I could cavitate the prop coming on plane.... but... top end was 98.8 at 5980 rpm. The boat was so stable, that I was able to look over my shoulder to see how the innercooler water was shooting out of the side of the boat, played with the trim to see what it did to the GPS speed, and gave my son a "high five". We were at over 97.5 mph for over 2 minutes. Wowser! this thing is finally driving like I thought it should... it felt like it was effortless, and on rails!
I am going to try a Merc Lab 28 next to see if I can get some more speed. My peak horsepower is at 6200 rpm. I am looking to break the century mark on pump gas, with an extremely stable boat.
I will still be using a P5x for my daily driver, and when taking the kids out wakeboarding... except for going over 90mph.
I will also be trying the boat with the 1/2 spacer removed to see how it works with both 4 and 5 bladed props on my boat.
Chris
The boat was a handful over 93 mph, and was rocking from side to side as the prop torque rolled the boat to the left, and then the hull corrected itself. Definately not for the faint of heart.
Since then, I have decided to concentrate on boat handeling.
To this end, I purchased a new 1" shorter IMCO lower unit with 1.34 gears. The theory was that by using smaller pitched props, the blades would be more verticle to the water, causing less prop torque. Also, by experimenting with shorter outdrive lengths, the prop would have less leverage to roll the boat, and that the shorter lower unit would cause less drag. While working on Jim's 700 Ilmor boat, I discovered that it was the fastest with a 3" propshaft depth, and that at 2.5" , it lost speed, and would not hook up coming on plane even with a P5x. The smaller raked props also have the advantage in that they usually have lower slip numbers than their bigger brothers
I have discovered that over about 93 mph, that the four blades work better on my boat than the P5x does. The four blades have less blade area, lift the rear of the boat less, and don't have as much surface area to prop load the boat.
I removed the 1/4 inch smaller pulley, and filled the boat with 92 octane unleaded pump gas.
My first run was done using a 1/2 inch spacer (3" propshaft depth), and a 27 P5x. The boat still hooks up great on the bottom end, had a 43 mph cruise at 3000 rpm and topped out at 95.2 mph. Over about 91, the boat became a handfull to drive as it started doing the prop torque dance, rocking the boat from side to side at over 90 is no fun.
Next I installed a friends stock 28 merc prop. Cruise speed was down some to 40 mph at 3000 rpm, and I could cavitate the prop coming on plane.... but... top end was 98.8 at 5980 rpm. The boat was so stable, that I was able to look over my shoulder to see how the innercooler water was shooting out of the side of the boat, played with the trim to see what it did to the GPS speed, and gave my son a "high five". We were at over 97.5 mph for over 2 minutes. Wowser! this thing is finally driving like I thought it should... it felt like it was effortless, and on rails!
I am going to try a Merc Lab 28 next to see if I can get some more speed. My peak horsepower is at 6200 rpm. I am looking to break the century mark on pump gas, with an extremely stable boat.
I will still be using a P5x for my daily driver, and when taking the kids out wakeboarding... except for going over 90mph.
I will also be trying the boat with the 1/2 spacer removed to see how it works with both 4 and 5 bladed props on my boat.
Chris
Last edited by CB-BLR; 06-26-2010 at 06:22 PM.
VIP Member
06-26-2010, 02:25 PM
#5
Chris
Gold MemberThread Starter
The boat looses a full 3mph + with the bow cover off.
Robert would probably love a 100mph ride in the bow, with the cover off... doing the Titanic movie thing....but Gina (mom) would kill me!
Chris
Last edited by CB-BLR; 06-26-2010 at 03:34 PM.
06-26-2010, 04:45 PM
#7
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It sounds like an expensive disease that you have. You should consider therapy. OH wait... This is therapy.
All kidding aside, great numbers and good luck and be careful.
I'm not nearly as fast as that, but I get the same feeling with the P5X as you do. It just makes the boat a little crazy at higher speeds. It feels like the P5X gives the boat stern lift. The 4 blade bravos seem to work best for me.
All kidding aside, great numbers and good luck and be careful.
I'm not nearly as fast as that, but I get the same feeling with the P5X as you do. It just makes the boat a little crazy at higher speeds. It feels like the P5X gives the boat stern lift. The 4 blade bravos seem to work best for me.
06-26-2010, 06:43 PM
#9
Chris
Gold MemberThread Starter
"Therapy"
defined as the treatment of a physical or mental desease by means other than surgery. .. My wife is a Nurse Practitioner.
Chris
06-27-2010, 09:25 AM
#10
Registered
Way to go Chris. I think you are the first and only OB Heat to 100. Not easy to do on any big single engine hull, open or hard deck.
Congratulations,
Steve
Congratulations,
Steve
Last edited by Steve Zuckerman; 06-27-2010 at 06:37 PM.
