SoCal Jet Boats

Tech Talk => Jet Pumps => Topic started by: 79charger on May 08, 2011, 06:24:27 PM

Title: Is my impeller to conservative ???
Post by: 79charger on May 08, 2011, 06:24:27 PM
Had my jet rebuilt this winter and decided to stay with a "A" impeller . I figured my BBF around 450-500 Hp .....Well after all the little bugs were worked out I run at 4300 RPM at full throttle around 65-68 MPH . That RPM seems bit high . But it runs so great with no cavitation issues and has a great holeshot . I just dont want to trash the motor ,because I love to mash it . Thanks
Title: Re: Is my impeller to conservative ???
Post by: gregb on May 08, 2011, 06:34:21 PM
Is your tach accurate and working properly?  Have to ask, that RPM seems kinda low for the HP you are claiming. 
Title: Re: Is my impeller to conservative ???
Post by: Ralph Brunt on May 08, 2011, 06:41:31 PM
Is your tach accurate and working properly?  Have to ask, that RPM seems kinda low for the HP you are claiming.
x2
Title: Re: Is my impeller to conservative ???
Post by: Dirty Air on May 08, 2011, 06:43:05 PM
Sounds to me like its set up perfectly. My tunnel at 4300rpm was right at 71mph, so mid 60's out of what I guessing is a v-hull sounds really good. As for 4300rpm if the motor is build descent (good rod bolts,proper clearances, balanced properly....ect.) I think your in good shape. But with a larger Imp. A+ or AA will pull RPM down and probably lose top speed.
Title: Re: Is my impeller to conservative ???
Post by: 79charger on May 08, 2011, 06:54:06 PM
I believe my tach is fine .....  Let me give you some more info . The boat is a 22 Mini Day cruiser , Has 460 with, 10.5.1 compression, Roller rockers , Comp Cam XM296HR , Weiand Stealth Intake , Holley 750 double pumper Vaccuum secondary .And runs Harmann long bolt logs ...... I thought 450 was pretty conservative guess for that build . Well I wont screw with success ...So I will run it . Thanks


Title: Re: Is my impeller to conservative ???
Post by: Ralph Brunt on May 08, 2011, 06:59:34 PM
charger, that makes even less sense since it is a 22foot boat, that speed and rpm dont match for that size boat.

that motor should pull an A impellor 5k
Title: Re: Is my impeller to conservative ???
Post by: 79charger on May 08, 2011, 07:10:18 PM
Well I will check my tach first and then check my jetting again ......
Title: Re: Is my impeller to conservative ???
Post by: jet boat performance on May 08, 2011, 07:11:55 PM
Is your tach accurate and working properly?  Have to ask, that RPM seems kinda low for the HP you are claiming.

Xs 3 450 to 500 HP=4900 rpms =an "A' Impeller ....
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