what is your top speed, prop setup for 272 owners
01-13-2013, 11:36 AM
#21
Registered
iTrader: (1)
Join Date: Jan 2012
Location: Sunny Isles Beach,Fl.
Posts: 499
Likes: 0
Received 0 Likes
on
0 Posts
Diego...as a matter of comparison, my '86 272 LS with twin 320 EFI SBC's thru Alpha SS drives would run 74~75 with 23" Cleaver props. The RPM was pushing 6000 depending on the drive trim. The swim platform on mine was teak on brackets with thru hull exhaust. The 320's were stock except for the addition of a larger Lingenfelder throttle body..they made solid power past 5500 RPM. There was another OSO member that had a boat like mine that was the '86 272 LS Miami Boat Show "Demo" boat. He changed the engines in the early '90's to LT-1 350 SBC's and reported 754 MPH top speeds. http://www.offshoreonly.com/forums/f...-vs-272ls.html If I recall the SS drives had a short lower unit which may have helped the top speed due to a shorter "X" dimension. Shorter lower units on Bravo I's may be a quicker ticket to more top end for you than more power. B-I's do run a deep "X" on our boats due to the hull configuration.
The EFI was revolutionary for the times...but "Cave Man" compared to today's MPI systems. The thing I truly enjoyed about the boat was being able to start the engines after sitting idle for a month with a simple twist of the keys. No throttle pumping was required...they started first time...every time.
The EFI was revolutionary for the times...but "Cave Man" compared to today's MPI systems. The thing I truly enjoyed about the boat was being able to start the engines after sitting idle for a month with a simple twist of the keys. No throttle pumping was required...they started first time...every time.
You were probably pushing over 400 hp a side to get those numbers, I agree on the shorties, They could add more speed , Ian , the guy with the fastest 272 I have heard of , gain lots of speed with shorties and ditching the swim platform .
Ps : I am getting you measurements today.yesterday boat was on the water when I got there.
01-13-2013, 12:57 PM
#22
Registered
iTrader: (2)
Diego...as a matter of comparison, my '86 272 LS with twin 320 EFI SBC's thru Alpha SS drives would run 74~75 with 23" Cleaver props. The RPM was pushing 6000 depending on the drive trim. The swim platform on mine was teak on brackets with thru hull exhaust. The 320's were stock except for the addition of a larger Lingenfelder throttle body..they made solid power past 5500 RPM.
If I recall the SS drives had a short lower unit which may have helped the top speed due to a shorter "X" dimension. Shorter lower units on Bravo I's may be a quicker ticket to more top end for you than more power. B-I's do run a deep "X" on our boats due to the hull configuration.
If I recall the SS drives had a short lower unit which may have helped the top speed due to a shorter "X" dimension. Shorter lower units on Bravo I's may be a quicker ticket to more top end for you than more power. B-I's do run a deep "X" on our boats due to the hull configuration.
OK, 6k rpm through 1.5 drives pushing 23 cleavers with 15% slip is 74 mph, numbers seem reasonable. and yet a 272 with standard alpha's and 300 hp per side will be maybe a 65 mph boat from what I hear. That is a heck of a difference.
I am surprised as the boat manufacturers love bragging rights and the cost of more HP is very high in new boats. It seems like they would have caught onto this and put it in newer boats also. I mean the new 292 is close to the old 272, has a stepped hull and only runs as fast as your old 272 with the bravo's and 6.2's. I just don't get it.
People pay big money for HP to go 5 mph faster. If you could do it with a set of new alpha lowers without having to mod your motors or stress them more, seems like a market that is untapped for a new product. Any plans for SEI to make a shorty lower alpha?
[/IMG]
[/IMG]
[/IMG]
[/IMG]
01-24-2013, 07:17 PM
#24
Registered
iTrader: (1)
Join Date: Jan 2012
Location: Sunny Isles Beach,Fl.
Posts: 499
Likes: 0
Received 0 Likes
on
0 Posts
I put back a set of mirage 25's and got 63 mph at 4200 rpm , but with 23's I am over 5000 rpm which I don't like it on my 330's . Does this sound right? Full throttle I would pass 5000 rpm with the 23's and with 25's won't go over 4200 rpm. Anybody?
01-24-2013, 08:07 PM
#25
With the 23's, 65mph at a little over 5000 is about 12% slip which is probably accurate for a twin engine boat.
With the 25's, 63mph at 4200 is 4.8% slip. Sorry but old convential hulls arent that good so somethings is off.
Are they worked to 27s or something?? 27s at that speed and rpm would put you back in the 12% slip range.
With the 25's, 63mph at 4200 is 4.8% slip. Sorry but old convential hulls arent that good so somethings is off.
Are they worked to 27s or something?? 27s at that speed and rpm would put you back in the 12% slip range.
01-24-2013, 08:52 PM
#26
Registered
Join Date: Mar 2011
Location: Dover DE
Posts: 192
Likes: 0
Received 0 Likes
on
0 Posts
1988 272 SR-1
25 mirage props
54 MPH
454 peanut port heads with rectangular port intake
4000 rpm on the starboard motor and 3600 rpm on the port
Was told 300 hours buy the seller, but found a hourmeter in the cabin with 900 hours showing.
25 mirage props
54 MPH
454 peanut port heads with rectangular port intake
4000 rpm on the starboard motor and 3600 rpm on the port
Was told 300 hours buy the seller, but found a hourmeter in the cabin with 900 hours showing.
01-26-2013, 01:39 AM
#27
Registered
iTrader: (1)
Join Date: Jan 2012
Location: Sunny Isles Beach,Fl.
Posts: 499
Likes: 0
Received 0 Likes
on
0 Posts
With the 23's, 65mph at a little over 5000 is about 12% slip which is probably accurate for a twin engine boat.
With the 25's, 63mph at 4200 is 4.8% slip. Sorry but old convential hulls arent that good so somethings is off.
Are they worked to 27s or something?? 27s at that speed and rpm would put you back in the 12% slip range.
With the 25's, 63mph at 4200 is 4.8% slip. Sorry but old convential hulls arent that good so somethings is off.
Are they worked to 27s or something?? 27s at that speed and rpm would put you back in the 12% slip range.
Of course speeds were all gps'ed
I will test this again tomorrow with the 25's just to double check the rpm
01-26-2013, 01:56 AM
#28
Registered
iTrader: (2)
Join Date: Aug 2005
Location: Between A Womans Leggs in IL
Posts: 6,306
Likes: 0
Received 1 Like
on
1 Post
fixx
put the 25's on,when on plane trim the drives up just until the props start to slip then ease into the throttle,,my old ls when it had twins that would be how it ran the fastest with the 27's and a little slip .....
01-26-2013, 08:33 AM
#29
Registered
I'll ask Tommy who is go to guy is down here for dialing in props...we'll get you fixed up eventually!!
