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New 21 Pulsare setup! 93-94 mph!

The only thing I have seen out of the simon motors are that they are a bit quicker. It takes a lot of cash to gain top end. One of our members(docked wages) had a 225 efi on a 21 Liberator that ran 83 stock. After a bunch of work and 7 1/2 truck loads of money, he managed 104. Some of his parts and ideas came from Eric Simon. That was 1 mph faster than his friends identical Lib with a 300! With the 225 and 300x being the same cubic inch, it can be done. But it's cheaper to just buy a 300! My $.02
 
WILDMAN,those are very respectable numbers for the 21 and the 24 to come from a go fast ski/family boat with stock motors.Keep up the good work.
PS----you did a good job on Dixons boat.
JB in Sav
 
I'll try a 30" prop this week to keep it off the limiter and bring the rpm's back down into the power range
 
Randy, I'm curious. . . are you saying the modified motors don't make more power than stock, or the setups aren't taking advantage of the power?
 
engineermike said:
Randy, I'm curious. . . are you saying the modified motors don't make more power than stock, or the setups aren't taking advantage of the power?
Click to expand...

Gotta be setups.... more HP = more speed in any application, up to a certain point. No way that 390HP simonized X spinning a ridiculously expensive custom made 34P prop ain't gonna move a 21' faster than 300hp. Just sayin.
 
I'm just saying that I have not heard from anyone that the modded 300 motors have run bigger numbers than the stockers. I believe anything that can be proved to be true. Just never seen it yet.
I know a boat builder that ran 107 with a stock 300x. He sold the boat minus motor and the new guy put a -----335 on it. The boat builder set it up for him and even drove it to a best of 96 mph!
I had stock 260's on my twin 21 Liberator. It ran 116. I had them mildly modded and ran 127.8.
 
300HP vs 390 hp

I am with Randy on this one. It takes torque to twist the prop. I am sure the stock 300 will have more torque tan the built motor which needs high rpm to make hp.

Lets just say the built motor has 390 hp @ 8000 rpm. Using the equation to find torque, (390 x 5252 divided by 8000) your built motor has 256 lbs of torque at 8000 rpm.

At 6000 rpm the built motor will only have 292 hp (hp = torque x rpm divided by 5252). This assumes that the torque curve is flat at these rpm.

The stock motor has 300 hp at 6000 rpm with 263 lbs of torque. In the real world the 300 is probably about 10% more than 300 hp, which makes it about 330 hp and 289 lbs of torque at 6000 rpm.

Another problem is that if you put a larger prop on the built motor, it will not have the power at lower rpm to get it up into the power band.

The built motor would probably be faster on a very lightweight tunnel that could take advantage of the high rpm.

For a 21 ft Checkmate, the stock 300 is a better way to go most of the time. I know that there are exceptions, but lets don't go to outer space about this.

Remember more hp is just torque at a higher rpm. What you gain on the top end, you usually lose on the bottom end.

I hope that I explained this right and that it makes sense...............Skip
 
Any way you slice it, Randy has a bada$$ boat with bada$$ #'s plain and simple. :thumbs: Just wish the price tag wasn't so high!
 
The best setup secret is to run the boat at sea level. The rest anyone can do; mess with setback, height and prop.
 
Last time I heard, the "Simonized" powerhead was $8995 exchange. That's alot of money for 1 mph and taking the weight out of the boat! I guarantee that it will use more than double the gas too. At 4000 rpm, a stock 300x gets 3 mpg on a 21 Checkmate. The 300xs gets 6 mpg at the same rpm with the same prop.
 
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