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Author Topic: GT-150 speed stats  (Read 56998 times)

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Offline thedeuceman

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GT-150 speed stats
« on: June 13, 2013, 01:01:04 PM »
so far this is what i have seen with the GT-150, 73 115hp Johnson no power trim, trim pin in second hole from transom.
Laurie and i in the boat, 9 to 12 gallons of gas in the bow.
1, unknown ss prop (with a few small nicks), 5600 RPM, 42 MPH GPS
2, 14x19P alum, 4900 RPM, 43 MPH GPS
3, 13x19P alum, 6500 RPM, 41 MPH GPS
these next 2 runs were Friday evening at rathbun, BUT... when i got home i found that the choke detent had fallen apart so that data may be skewed.
4, 13x21P alum, 4800 RPM, 44 MPH GPS
5, 12.75x21 alum, 4800 RPM, 44 MPH GPS
repeated run #5 with new plugs from Jerry same numbers. (orig BU8H, replaced with L77V)
« Last Edit: June 13, 2013, 03:41:26 PM by thedeuceman »
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Joe
75 GT150 "SeaDeuced"... Its Back !!
92 16CSS "Attitude Adjustment" is for sale
75 CV-16V8, Project
74 CV-16... its Purple !

Offline wiliermdb

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Re: speed stats
« Reply #1 on: June 13, 2013, 01:42:51 PM »
My CVX 16 with the original 1977 (115) and the original 12 3/4 x 21 SST runs 47 -  48 GPS with two adults and approx. 12 gal of fuel @ 5300 rpms.
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Offline 84carlson

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Re: GT-150 speed stats
« Reply #2 on: June 13, 2013, 04:47:26 PM »
My CVX16 with a 1998 Johnson 115 and a 19" Stainless Steel is at 49mph loaded with 2-3 people onboard...I would invest in a power trim, that way you will get the most speed out of it...

Joe

Nebraska
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Offline Rosscoe

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Re: GT-150 speed stats
« Reply #3 on: June 13, 2013, 07:40:06 PM »
6500 RPM?!  :o
Seems a bit high, just a bit. I would think doing that would be bad for any length of time but  it is an OMC and I'm less familiar with them, then Mercs.
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Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline Hyperacme

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Re: GT-150 speed stats
« Reply #4 on: June 13, 2013, 08:13:47 PM »
Leave Laurie at the dock, light load of fuel, trim pin out one more hole ... and shot for 45 mph !
T&T should be good for at least 3 mph, and is priceless for tilting at beach and loading on trailer ! ! !
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Offline David CVX-16

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Re: GT-150 speed stats
« Reply #5 on: June 13, 2013, 08:42:54 PM »
A 20" stainless steel Raker would help your top speed. Miles ahead of an aluminum prop. On a Glastron trip, you will have to try mine.
« Last Edit: June 13, 2013, 08:45:02 PM by David CVX-16 »
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David
87' CVX-16, 85' 115 HP Johnson, 58.8 MPH GPS w/ 23" SRX Prop

Offline thedeuceman

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Re: GT-150 speed stats
« Reply #6 on: June 13, 2013, 10:43:25 PM »
Gregg... It does have tilt, and 3rd hole did not appear to help any on top speed.

David... Looking forward to it :D
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Joe
75 GT150 "SeaDeuced"... Its Back !!
92 16CSS "Attitude Adjustment" is for sale
75 CV-16V8, Project
74 CV-16... its Purple !

Offline Rosscoe

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Re: GT-150 speed stats
« Reply #7 on: June 14, 2013, 09:41:09 PM »
Just to be clear, we know that "trim" and 'tilt" are 2 different animals, right?
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Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline thedeuceman

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Re: GT-150 speed stats
« Reply #8 on: June 14, 2013, 09:52:12 PM »
Quote from: Rosscoe on June 14, 2013, 09:41:09 PM
Just to be clear, we know that "trim" and 'tilt" are 2 different animals, right?
Yep...
The 73 115 I have on the GT is power tilt only, though now I'm looking for another "external trim" like the one I sold :/
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Joe
75 GT150 "SeaDeuced"... Its Back !!
92 16CSS "Attitude Adjustment" is for sale
75 CV-16V8, Project
74 CV-16... its Purple !

Offline thedeuceman

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Re: GT-150 speed stats
« Reply #9 on: August 30, 2013, 08:50:53 AM »
updates...
installed external power trim with a mercruiser pump mounted under splash well just before going to redwing.
trim tab was set full right (starboard) cuz that's where it was when i got the motor.
in redwing with just me and about 12 gal of gas i got 47 GPS @ 5800 with the stainless mystery prop, 49 GPS @ 5200 with Davids 20" raker.
when fully trimmed the torque steer was bad with Mystery prop, unbearable with the 20" raker.
moved the trim tab full left (port) torque steer way better at top speed but it pulls to right at moderate speed (30mph)
tested on the river last night with laurie, 2 dogs, gear, beer, extra props...
mystery prop, trim tab full left 43 GPS @ 5500
removed trim tab, 44GPS
tried alum OMC 14 x 19" , 44 GPS @ 4800
what i take from this is i will be running without the trim tab (will cut one off and fill the hole)
and will see where the mystery prop gets me.
may try Sean's 21" alum props again.
unfortunately Davids 20" raker is not in my budget right now :(
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Joe
75 GT150 "SeaDeuced"... Its Back !!
92 16CSS "Attitude Adjustment" is for sale
75 CV-16V8, Project
74 CV-16... its Purple !

Offline Hyperacme

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Re: GT-150 speed stats
« Reply #10 on: August 30, 2013, 09:13:53 AM »
Your best "Speed secret" is leavening Laurie at the dock ... LOL
Don't tell her I said that ...
At 49 mph are things getting a little light/loose ?
Maybe lift your motor ...


Have you read through this thread ?
http://www.classicglastron.com/phpbb/viewtopic.php?f=103&t=4613
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Offline thedeuceman

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Re: GT-150 speed stats
« Reply #11 on: August 30, 2013, 09:26:17 AM »
Quote from: Hyperacme on August 30, 2013, 09:13:53 AM
Your best "Speed secret" is leavening Laurie at the dock ... LOL
Don't tell her I said that ...
At 49 mph are things getting a little light/loose ?
Maybe lift your motor ...


Have you read through this thread ?
http://www.classicglastron.com/phpbb/viewtopic.php?f=103&t=4613
Yes... i will be doing lightened up solo runs
it was light but not as bad as i expected, the torque steer was too much but i think i have that fixed (trim tab removal)
need more time to know for sure.
i don't think i can go to 3rd hole with stock steering arrangement.
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Joe
75 GT150 "SeaDeuced"... Its Back !!
92 16CSS "Attitude Adjustment" is for sale
75 CV-16V8, Project
74 CV-16... its Purple !

Offline thedeuceman

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Re: GT-150 speed stats
« Reply #12 on: August 30, 2013, 09:38:58 AM »
Thinking about it, it seems odd that I would lose 4 miles an hour just loading the boat down.
The river was like peas soup, maybe that was slowing me down ;)
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Joe
75 GT150 "SeaDeuced"... Its Back !!
92 16CSS "Attitude Adjustment" is for sale
75 CV-16V8, Project
74 CV-16... its Purple !

Offline Hyperacme

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Re: GT-150 speed stats
« Reply #13 on: August 30, 2013, 10:07:00 AM »
Your best speed will be on the day the lake/river has a light chop, wind at your back of 30 mph and going down stream with strong currant ...
It will only happen once or twice a year ... So take a picture of your GPS when it does ... LOL

I get a 1 or 2 mph difference just from full tank to 1/4 tank ... 18 gal. tank ...
Outboards HATE weight !

EDIT ...

Bay Star will solve your toque steer problem but will run ya $500 plus ...
« Last Edit: August 30, 2013, 10:43:43 AM by Hyperacme »
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Offline Rosscoe

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Re: GT-150 speed stats
« Reply #14 on: August 30, 2013, 07:45:00 PM »
49 is impressive! I would think it would get a bit squirrely.
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Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline V153

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Re: GT-150 speed stats
« Reply #15 on: August 30, 2013, 10:25:47 PM »
Ya 49 ain't bad Joe, considering ...  When you run these shorter hulls it's amazing how any additional weight will affect yer top end?

Terry Currans scrawny a** slowed me down 2 - 3 mph ...
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'81 Baja 15SS_140 Frankenrude_66.7 mph
'70 something SpeedCraft_(Allison 16R Clone)_69.0 mph
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'71 V153_54.8 mph_wrecked


WALK TALL AND CARRY A BIG BILGE PUMP

Offline David CVX-16

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Re: GT-150 speed stats
« Reply #16 on: August 30, 2013, 11:58:31 PM »
I would not remove the trim tab. Streamline it instead. I plan on doing this soon. My trim tab is fully to portside. Plan to remove the end curl on the starboard side and make the front of the fin sharper. Maybe even take some metal off the inside pivital point so that it turns more portside. Have given up on the huge trim tab - slows the motor down too much.

Joe, you will not find a faster prop than a Raker.
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David
87' CVX-16, 85' 115 HP Johnson, 58.8 MPH GPS w/ 23" SRX Prop

Offline MarkS

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Re: GT-150 speed stats
« Reply #17 on: August 31, 2013, 05:17:16 AM »
Quote from: Rosscoe on August 30, 2013, 07:45:00 PM
49 is impressive! I would think it would get a bit squirrely.
Each hull is probably a little different, and Joe's weight distribution is more forward than mine, but mine doesn't get really unstable until about 52 or 53 mph, Ross.  (Different props make the boat act differently at WOT as well!)  The one run I got to 54 mph was "riding the ragged edge".  :o

Great to see you're getting her sorted out Joe, they're a small boat but A LOT of fun!
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Mark
1978 SSV-176

Offline thedeuceman

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Re: GT-150 speed stats
« Reply #18 on: August 31, 2013, 08:16:37 AM »
This is a really fun boat, I really like how it handles an assume that is due to the weight in the front which also slows me down some.
I'm trying not to fixate on top speed, but...
David, I do "want" that prop, just top much other stuff to spend on now, like gas & oil.
In the end I would like to be able to say "it'll do 50"
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Joe
75 GT150 "SeaDeuced"... Its Back !!
92 16CSS "Attitude Adjustment" is for sale
75 CV-16V8, Project
74 CV-16... its Purple !

Offline David CVX-16

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Re: GT-150 speed stats
« Reply #19 on: August 31, 2013, 03:33:44 PM »
Joe, I sent you an e-mail.

David
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David
87' CVX-16, 85' 115 HP Johnson, 58.8 MPH GPS w/ 23" SRX Prop
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