Author Topic: GT-150 speed stats (Read 56975 times)

V153 · « **Reply #40 on:** September 08, 2013, 03:25:08 PM »

Tiny Tach:

Hyperacme · « **Reply #41 on:** September 09, 2013, 08:30:14 AM »

GCarlover ...
Thought about getting one (Tiny Tach) for my 1971 Merc 65 HP motor, years ago.
Emailed them and they responded with in an hour with model I needed ...

GCarlover · « **Reply #42 on:** September 12, 2013, 04:34:29 PM »

On the 22 High Performance 2 blade, why not hub it to a Johnson? How much is the cost of the hub? They had one on Ebay a while back for about $30. To grind the flange down, Put it on a 3/4 shaft and clamp upright on a drill press and use a mill cutter or a grindstone and rotate it by hand. According tomy measurements there is .050 difference which is .025 wall thicknes. Someone on Fiberglassics cut the flange off but he sold it. Would recommend leaving the flange to prevent blowout. I read on a site for rehubbing you need a funnel to keep the rubber from spreading. Don't know if we have any prop shops around here anymore.

David CVX-16 · « **Reply #43 on:** September 12, 2013, 04:45:13 PM »

I toyed with the idea of using either the 21" or 22" 2-blade bronze prop and rehubbing to a Johnson, but considering the smoothness and bow lift abilities of the OMC Raker 22" or SRX 23", I doubt that the 2-blade bronze prop would be better.

Someone on Fiberglassics had a 24" Hi-Performance Mercury Quicksilver 2-blade bronze for sale, but then one would have to have it repitched to a 23", whereas a 22" might be the best pitch.

thedeuceman · « **Reply #44 on:** June 19, 2014, 02:19:21 PM »

stats from rathbun last weekend
all excess gear piled up on beach, less than 1/4 tank of fuel
mystery prop (for comparison) 47.? @ 6K
banged up 20" raker 49.1 @5400
after the nick is welded up, and David thins and balances it we will test again.

David CVX-16 · « **Reply #45 on:** June 19, 2014, 02:38:49 PM »

Touching up the prop makes a big difference. Let me know when you are ready.

Jason · « **Reply #46 on:** June 19, 2014, 02:47:29 PM »

SO CLOSE TO 50!!

David CVX-16 · « **Reply #47 on:** June 19, 2014, 05:22:33 PM »

Fellow on the national Glastron site with 1987 120 HP Johnson setback jack, SRX 27" prop, etc running 64 MPH.

" Alright fellers...

I've been watching this thread for a long time and have yet to see any progress made so I thought I'd jumpstart it this year.

My GT 150 is a 1974 I rebuilt completely (minus the pretty gelcoat). The extent of the modifications was removing the ski locker and making the stringers and transom thicker.

I started with a 1978 115 Rude that would put me to 50mph wit a 19" OMC SST. I blew up the #1 cylinder on that motor. Then I got a 1987 110 Rude and was pushing 52.5mph with the same 19" prop. then I got my hands on three 23" SRXs!!!! Mounted high up and turning 6250rpms I was able to consistently hit 55mph all day with no trouble. BUT the small gearcase on the V4 Crossflows requires the use of extreme trim which results in extreme chinewalk
Stock SRX - 53.5
Spinelli Brothers SRX - 55.3
DAH SRX - 56.6
Then the 110hp blew the crankcase seal, it was still getting me 55mph but was making a mess of my splashwell and midsection so I retired that motor.

Now I have a 1987 120hp Johnson looper. the V6 gearcase is a 2.25:1 ratio and I'm turning a 27" SRX at 6200rpm and is smoothly pushing 64mph!!!!!!!!!!!!!

I have it on a Hi-Jacker with 6"setback and propshaft is set 5in below.
Converted it to tilt tube steering and I have no chine walk at 60+.... I drive it with one hand at those speeds no problem. The motor is stock except for pulling the VRO and putting a new diaphragm style pump on it from V6.

My 60MPH setup:

1987 120HP Johnson with top two holes plugged
27" OMC SRX
6in set back jackplate
Hot Foot throttle
steering wheel trim.
14 gallons of fuel in the back
battery in the back on the port side
lifejacket with kill switch
beer in my left hand and the other on the wheel

60+ Glastron GT150

Ive only had this motor on for 5days so after setup I should be able to get up to get over 65mph.... cause we all know 70mph in a GT is just stupid

here's a screenshot from a video I filmed while driving with one hand the other day, before I raised the motor higher."

MarkS · « **Reply #48 on:** June 20, 2014, 03:05:49 PM »

Very respectable Joe, I laughed when I saw Laurie post the pic on FB with the gear stashed on the beach!

Can't argue the "new guy's" stats David, it appears he has broken through the barrier with his set-up. At first I thought it was probably B.S., but who am I to question? I was told by numerous people the GT-150 hulls would not perform well with any set back, maybe they were wrong.

Hyperacme · « **Reply #49 on:** June 20, 2014, 06:16:37 PM »

" At first I thought it was probably B.S., but who am I to question? "

If it's post on the internet it has to be true .... Right ?

I read his post the other day .. I don't know, he only has one post ... Doug getting that speed with out a set back ... but he isn't sitting back drinking a beer with one hand on the wheel ...

If a 6 inch set back can get me to the high 50's with out handling issues ... I'm getting a 6 inch set back !

I don't know ...

V153 · « **Reply #50 on:** June 20, 2014, 07:19:52 PM »

I don't believe he's going anywhere near that fast in the vid.

V153 · « **Reply #51 on:** June 20, 2014, 07:26:52 PM »

Quote from: Hyperacme on June 20, 2014, 06:16:37 PM

... but he isn't sitting back drinking a beer with one hand on the wheel ...

Well ... sometimes ...

Hyperacme · « **Reply #52 on:** June 20, 2014, 07:59:28 PM »

" Well ... sometimes ... "

OK .. I was wrong ...

David CVX-16 · « **Reply #53 on:** June 20, 2014, 09:38:28 PM »

Yes, something does not seem right. But even if it is, it is not a boat that can go fast in rough water - too short of a boat. Notice how smooth the water is.

The tests of my 23" SRX's on White Bear Lake were in choppy water, yet the boat felt safe at all times, no chine walk, no yanking, no porposing at 55 to 56 MPH. The NFB steering means I can take my hands off the steering wheel and it will not turn. Feeling and being safe mean alot.

Hyperacme · « **Reply #54 on:** June 20, 2014, 09:51:04 PM »

OK Joe ...
Ya need a 6 inch set back and more HP ...
Maybe a 150 HP ETEC or something like that, so ya can hit 70 mph and put this guy to shame ...

Dave ...
Did the guy you met at Lions levee with the fancy black CVX16 have a Jack plate on it ?
Remember you posted pictures a short time ago ...

V153 · « **Reply #55 on:** June 20, 2014, 10:23:27 PM »

More HP cain't hurt. But in the meantime have David rework that Raker for you Joe. You need to be spinnin that prop, or one just like it, closer to 58-5900 @ wot. Then y'oughta easily crack the 50 mph mark.

V153 · « **Reply #56 on:** June 20, 2014, 10:45:09 PM »

Quote from: David CVX-16 on June 20, 2014, 09:38:28 PM

it is not a boat that can go fast in rough water - too short of a boat. Notice how smooth the water is.

Zacly! Too short. (And wide.) The GT 150 is unlike the "V" series hulls. Including the GT 160. The 150's more of an "air slot" kinda hull. It's only gonna go so fast, then something bad's gonna happen ...

edit. Plus you can smoke one in a V153 with comparable power. Chop or not.

David CVX-16 · « **Reply #57 on:** June 21, 2014, 04:24:43 AM »

The fellow at Lions Levee was a perfectionist and one who tried everything to make his CVX-16 go fast - blueprinting the hull, jackplate (see attached picture, it appears to be less than 6"), raising the motor a bit at a time, and experimenting with Laser II props. When we met him, he was running a 22" Laser, then switched to a 24" Laser and went about 60 MPH (a 26" Laser was too steep). He tried to design a low water pickup system to raise the motor even higher, but that did not work.

In my opinion, he could have gone faster by usiing a Mercury 24" Chopper prop and using a jackplate with more setback.

Remember Conrad Schmidt was raising his Mercury 1500 XS to the extreme by usiing a defecter system to feed water into the inlets, and hit 80 MPH in his Glastron Contender using a 28" Chopper, I believe.

Carlson Contender 1500 XS 1975

In this video he is going 70 MPH but constantly improved his speed and reached his goal of 80 MPH. Sold the boat and is now working on another project.

MarkS · « **Reply #58 on:** June 21, 2014, 05:26:05 AM »

Quote

Sold the boat and is now working on another project.

Yup, but KEPT the Merc 1500 XS!

Milkdud (Conrad) has been way too quiet lately, wonder what he's up to? How about running over there and finding out Doran?

Glad I wasn't the only one skeptical about the speed report of 60+, but I hate to "call somebody out" without proof! (I agree the video does NOT look like anything over about 50 mph IMHO.) The prop size and measurements don't make sense to me either, but I'm just a rookie at the speed game. A 120hp swinging a 27" pitch at 6200 rpm sounds unlikely, and the

Quote

propshaft is set 5in below

sounds awfully high to me. (Mine is 6 1/2" below the keel, without a jack plate.) That's in the second hole up, it's the exact distance from the anti-cavitation or anti-ventilation plate which is level with the keel on my boat? I guess the set-back would allow you to run higher, but without a low water pickup???

IF it's true, more power to him. BUT I don't want to be on the same water if he's driving around with a beer in his hand!!! Nothing wrong with a cold libation, but wait until you're OFF the water or not behind the helm, PLEASE.

Dougie, I'm going to ignore your V-153 smokin' the GT-150 comment (again), 'cause I love you brother!

Gregg, I can't imagine hanging a 400+ pound outboard off the back of a GT-150, I'd be afraid a ripple would swamp the boat! The 300+ pound V4 is plenty, for me anyway.

Thanks for allowing my incessant ramblings, up too early as usual....

PS - Joe I am sorry for trashing your thread. You and I might not be the fastest GT-150's on the water, but we look good! Ha ha

Hyperacme · « **Reply #59 on:** June 21, 2014, 06:42:57 AM »

Mark ...
" The prop size and measurements don't make sense to me either "

Me either !
He has the GPS shot though ...

I was J/K about the 150 HP motor.
I've though a 90 HP Yamaha (about 250 lbs. 3 cyl.) would be cool to try.
Mark (catchaedge) is getting 48 mph out of his 85 HP Merc w/o T&T, bet the Yamie would get over 50 mph pretty easily ...

Dave ...
The black CVX could be a 6 inch, maybe 4 inch ?