99 271 fastech trying reach 80mph please help
05-31-2018 | 08:51 PM
#12
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Basically I walked in to shop said I had to spin a 30 at 5500 to get at least 80 mph he said oh I can do that for ya so I payed the guy and he removed installed the new motor and I trailered it home to test it by myself because he said he no way of putting it in the water so after buying 2000 dollars in props and a bunch of time the best I got was 73 w a 4 blade 28 and I have oil leaking all over builder that we still don’t have. A date to correct maybe next week he said in writing I just have a few notes and the prices for all the additional work like paint job rand r and on the heading it says 700 hp there is no way it’s 700 hp any advice on my next move would be greatly appreciated the motor sounds good but it doesn’t push the boat to the speed I payed for I told him I want an 80 mph. BOat didn’t haggle the price I payed an enormous amount of money for 5 mph at best I feel like I’m stuck ina position
05-31-2018 | 09:23 PM
#13
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Well... The motor Im finishing should make about 625...Im praying to kiss 80 and that is a 22 foot boat thats a LOT lighter than yours.....
Dry weight best I can find is about 5750,,,given the fact that every mfg's dry weight number is more optimistic than it pitot speedo, with gear people fuel, beer cooler etc your probably looking at 7000 pounds. so when we plug 7000 pounds.+ a constant of 240 ( resonabley good shape single step bottom), 675 hp and an optimistic 8-9% slip. into the bam speed calculator (which is pretty good when given realistic infornation) you get a top speed of 75 mph, per the calculator to hit 80 you need at least 778 hp. blueprint the bottom, put the boat on a diet, you can get close with 675 hp Also when doing the math with your max 71 speed, your motor (if everything else is good) is making about 100 hp less than claimed....
Dry weight best I can find is about 5750,,,given the fact that every mfg's dry weight number is more optimistic than it pitot speedo, with gear people fuel, beer cooler etc your probably looking at 7000 pounds. so when we plug 7000 pounds.+ a constant of 240 ( resonabley good shape single step bottom), 675 hp and an optimistic 8-9% slip. into the bam speed calculator (which is pretty good when given realistic infornation) you get a top speed of 75 mph, per the calculator to hit 80 you need at least 778 hp. blueprint the bottom, put the boat on a diet, you can get close with 675 hp Also when doing the math with your max 71 speed, your motor (if everything else is good) is making about 100 hp less than claimed....
05-31-2018 | 09:39 PM
#14
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From: Toledo Oh
05-31-2018 | 10:25 PM
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From: Toledo Oh
That helps..since any input can be the variable, if we put in 5900# 600 hp and 72 mph we get a constant of 225, no remove the hp and plug in 80 mph he is going to need 739 hp and if he is puching a 6000 single with 740 hp, he is going to need a new bravo real soon....
06-01-2018 | 06:48 AM
#18
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From: Toledo Oh
Whats the compression of your motor?? whats the valve train/cam? Do you have someone that can tune it? Thats a decent size boat with a bravo. are you ready to upgrade the drive and or replace it? Do you have the knowledge to properly setup the fuel system? is the oil system up to the task? Is your bank account comfortable with it??
06-01-2018 | 08:38 AM
#20
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You guys are great Comp is 9.8:1 has brodex Heads 360 cc dart block eagle crank I have a aero 1000 pump w a return line already plumbed also I have upgraded to Xr drive no my bank account is not happy so I’m trying to sell my 509 that ran great and the bravo drive all fresh water stuff w low hrs so that may help not sure what oil system has to do w it but everything u guys say I value greatly don’t want hurt the engine builder name but he sure missed the mark maybe a long winter had his intentions twisted
