454 making 525-550hp
10-16-2015 | 08:35 AM
#21
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Joined: Oct 2012
Posts: 896
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From: Buffalo NY
Imo, the 250 isnt a big enough upgrade from a 177, it is a better starting point however.
Even a 250 on a 454 making 5-6lbs of boost, will be 60+ percent overdriven, where a 177 will be 100+ percent. Imo, these small blowers work great on the street, where full throttle torque from idle to 5000 is the goal. Running 5000+ for extended periods in a boat, a larger blower like 671, 871, or 420 b&m is a better fit.
Even a 250 on a 454 making 5-6lbs of boost, will be 60+ percent overdriven, where a 177 will be 100+ percent. Imo, these small blowers work great on the street, where full throttle torque from idle to 5000 is the goal. Running 5000+ for extended periods in a boat, a larger blower like 671, 871, or 420 b&m is a better fit.
10-16-2015 | 11:30 AM
#23
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Joined: Feb 2004
Posts: 2,590
Likes: 173
From: Endicott, NY
Here is an old picture of my former Top Gun when I had the Chiefs. They were 671s but they were tall.
10-16-2015 | 02:53 PM
#25
Platinum Member
Joined: Oct 2002
Posts: 481
Likes: 7
From: blue point,ny
You need this. (B&M 250)
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[ATTACH=CONFIG]546548[/ATTACH]
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And 1 of these. http://www.mrcool.us/skin/frontend/d...ct-Listing.pdf
.
[ATTACH=CONFIG]546549[/ATTACH]
.
[ATTACH=CONFIG]546548[/ATTACH]
.
And 1 of these. http://www.mrcool.us/skin/frontend/d...ct-Listing.pdf
.
[ATTACH=CONFIG]546549[/ATTACH]
10-16-2015 | 10:26 PM
#27
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Joined: Jan 2003
Posts: 6,019
Likes: 1,521
From: Grand Rapids, MI
To be honest I was running I was running 2"x4" power steering coolers on my original Merc 420's. No temperature gauges. When I re-powered to ~600HP engines I put the 3"x18" on. I have never seen temps over 180*F after the cooler delivering the oil to my bearings and I run over 5500 RPM's for miles.
10-17-2015 | 01:12 AM
#28
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Joined: Oct 2013
Posts: 2,888
Likes: 148
From: SF Bay Area
Would putting a 250 blower on a GenV block with forged internals, aluminum heads, and 9.5:1 compression be too much? I'm just conceptually asking here as I plan out my motor. Or would you pull the pistons and lower the CR ratio?
10-17-2015 | 02:01 PM
#29
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Joined: Oct 2015
Posts: 7
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From: Canada NB
Hey guys,
I'm new to the forum and this is my first post. I cant seem to start my own discussion but This one seems somewhat comparable to what I'm doing. I have a 1989 Formula 242 LS. The boat originally had the 454 magnum (365) with GIL exhaust on it. I pulled the motor this season and had it completely rebuilt. I threw a Cam in it, punched it out 30 ,,new DART heads, bigger carb ,new exhaust ,,the whole deal. It came off the dyno making 526HP with 558 ft/lb of torque.
My question for anyone out there is what I should be looking at for a prop. I had a 21 pitch Mirage plus with the original block and it ran perfect...58 mph-61mph on a good day. My motor at peak performance now turns at 5300 RPM. I have plans to change my prop but I'm wondering if a 23 mirage plus 3 blade may be a bit small. Should I be looking at a 25 pitch Mirage plus?
I'm told these old formulas like the 3 blades, but any information would be helpful.
Thanks
I'm new to the forum and this is my first post. I cant seem to start my own discussion but This one seems somewhat comparable to what I'm doing. I have a 1989 Formula 242 LS. The boat originally had the 454 magnum (365) with GIL exhaust on it. I pulled the motor this season and had it completely rebuilt. I threw a Cam in it, punched it out 30 ,,new DART heads, bigger carb ,new exhaust ,,the whole deal. It came off the dyno making 526HP with 558 ft/lb of torque.
My question for anyone out there is what I should be looking at for a prop. I had a 21 pitch Mirage plus with the original block and it ran perfect...58 mph-61mph on a good day. My motor at peak performance now turns at 5300 RPM. I have plans to change my prop but I'm wondering if a 23 mirage plus 3 blade may be a bit small. Should I be looking at a 25 pitch Mirage plus?
I'm told these old formulas like the 3 blades, but any information would be helpful.
Thanks
10-17-2015 | 02:13 PM
#30
Registered
Joined: Oct 2013
Posts: 2,888
Likes: 148
From: SF Bay Area
Hey guys,
I'm new to the forum and this is my first post. I cant seem to start my own discussion but This one seems somewhat comparable to what I'm doing. I have a 1989 Formula 242 LS. The boat originally had the 454 magnum (365) with GIL exhaust on it. I pulled the motor this season and had it completely rebuilt. I threw a Cam in it, punched it out 30 ,,new DART heads, bigger carb ,new exhaust ,,the whole deal. It came off the dyno making 526HP with 558 ft/lb of torque.
My question for anyone out there is what I should be looking at for a prop. I had a 21 pitch Mirage plus with the original block and it ran perfect...58 mph-61mph on a good day. My motor at peak performance now turns at 5300 RPM. I have plans to change my prop but I'm wondering if a 23 mirage plus 3 blade may be a bit small. Should I be looking at a 25 pitch Mirage plus?
I'm told these old formulas like the 3 blades, but any information would be helpful.
Thanks
I'm new to the forum and this is my first post. I cant seem to start my own discussion but This one seems somewhat comparable to what I'm doing. I have a 1989 Formula 242 LS. The boat originally had the 454 magnum (365) with GIL exhaust on it. I pulled the motor this season and had it completely rebuilt. I threw a Cam in it, punched it out 30 ,,new DART heads, bigger carb ,new exhaust ,,the whole deal. It came off the dyno making 526HP with 558 ft/lb of torque.
My question for anyone out there is what I should be looking at for a prop. I had a 21 pitch Mirage plus with the original block and it ran perfect...58 mph-61mph on a good day. My motor at peak performance now turns at 5300 RPM. I have plans to change my prop but I'm wondering if a 23 mirage plus 3 blade may be a bit small. Should I be looking at a 25 pitch Mirage plus?
I'm told these old formulas like the 3 blades, but any information would be helpful.
Thanks
