Glastron GT-150 Ideal Prop for Slalom Skiing

[boatless bobby]

Greetings fellow boat lovers!

I have a propulsion related question that pertains to my Glastron Gt-150.

I bought this boat a few summers ago with the sole purpose of slalom skiing behind it. This past summer was a great one with waterskiing.

However this past summer myself and my skiing partner couldn't help feeling that boat was just lacking a tiny bit of speed. Perhaps 10% faster would have been the ticket. The boat has a 1997 2-stroke 70HP Evinrude on the back. I weigh 170 lbs and my skiing partner weighs slightly less (not that info really matters I suppose).

I come here today for some suggestions as to how to potentially eek out a little more top speed. My first thought is the prop. I am no professional at all when it comes to these things. However, is there a prop you guys can suggest that would produce the fastest top speed. To my knowledge the higher the pitch the higher the top speed. The lower the pitch the greater the torque on acceleration but a slower the top speed. I am thinking I would want a high (or perhaps highest) pitch option to get the top speed up when skiing.

Additionally, I have no idea what the pitch is of my current prop. Perhaps someone could help me out here. Lastly, you can see in the photos my prop and skeg is damaged, I suppose this would have slowed the boat’s top speed somewhat. I am going to look into having a new skeg welded on in this spring.


Anyway! Any advice whatsoever would be really appreciated guys! I would love it if I could get even just a little more top speed next summer on the lake!

 

[racerone]

I would start with a compression test .-----Post your numbers here.------If you want to go faster with a skier up , then you need a 100 HP motor !

 

[QBhoy]

I think you might squeeze a little more top end with a well set up stainless prop. But ultimately a 70hp on its best day is only really going to see late 30’s…40 at best without skiing and running light. So add a skier and gear and your likely down closer to 30. Ok for normal skiing but mono skiing maybe pushing it.
Anytime I’ve had a mono skier out the back…I’m sure I’ve been up around 34/35 mph gps towing guys that really know what they are doing.
If you don’t have much power to play with…it’s a tough one to get the prop balance spot on for speed and acceleration. Especially for mono deep water start.
The above is just ideal world stuff. No doubt it’s possible. But you’ll need to get it spot on with props I’d say. Very light shallow v boat for it too perhaps. Be easily pulled about by a mono skier

 

[Chris1956]

70HP is marginal for slalom skiing. A higher pitch prop could add some speed, but will reduce power, maybe until a deep water start is real difficult.
I have done deep water slalom starts where I had to take a breath and duck under the water, as the boat built speed, due to low HP. It certainly can be done. it depends on what is important to you.

Jump starts and their variants are good to use if you get a higher pitch prop, since you do not drag your body in the water.

 

[elsaylor]

...takes deep breath..."PULL" ..tuck into ball and hope.

looool good memories thanks!

 

[flyingscott]

Are you dropping a ski or getting up on one? I had one of those with an 85 Evinrude on it and 48-50 was my top speed. It would also be my last choice for a ski boat.

 

[boatless bobby]

Hey guys, thanks for all the responses! We only do deep water starts if we fall, otherwise we take off from the beach on one ski with the jump start method. Although I should add, even with a deep water start (1 ski or 2) the boat does decently well for pulling us out. I suppose it helps everyone weights between 155-170lbs.

What kind of prop does it look like the boat has now? I feel like it is on the higher end of pitch?

 

[racerone]

Most props have diameter and pitch marked or a part #.----Look for them.

 

[Texasmark]

70 HP isn't going to get you 35 mph for a slalom.

 

[QBhoy]

70 HP isn't going to get you 35 mph for a slalom.

Try telling Roger Moore that !

 

[flyingscott]

Try telling Roger Moore that !

Didn't 007s boat have an 85 hp V4 on it?

 

[QBhoy]

Didn't 007s boat have an 85 hp V4 on it?

Think they had about 3 different 150’s posing as one !! Haha.

 

[Texasmark]

Try telling Roger Moore that !

Roger Moore of James Bond fame bouncing Glastrons over land between waterways was running 135 HP Evinrude V4s. On the subject I forget how many Glastron (Austin, Texas mfgr.) the producer bought but it took more than one to get the shot.....correction 26 were purchased per the article:

Glastron GT-150

In the movie Live and Let Die (1974), James Bond uses a Glastron GT150 speedboat in a thrilling chase through the Louisiana marches. The boat made a record braking 120ft jump.The Live and Let Die GT150 used for the famous jump was built in 1972 and had an Evinrude Starflite 135hp engine.Two...

www.jamesbondlifestyle.com

Also you can bet Roger was sitting in his Austin Martin having martinis with his co-star probably while a stunt man was filming the scene. I liked Roger. Made one the better actors. Daniel Craig of current fame is doing a fine job also.

 

[QBhoy]

Roger Moore of James Bond fame bouncing Glastrons over land between waterways was running 135 HP Evinrude V4s. On the subject I forget how many Glastron (Austin, Texas mfgr.) the producer bought but it took more than one to get the shot.....correction 26 were purchased per the article:

Glastron GT-150

In the movie Live and Let Die (1974), James Bond uses a Glastron GT150 speedboat in a thrilling chase through the Louisiana marches. The boat made a record braking 120ft jump.The Live and Let Die GT150 used for the famous jump was built in 1972 and had an Evinrude Starflite 135hp engine.Two...

www.jamesbondlifestyle.com

Also you can bet Roger was sitting in his Austin Martin having martinis with his co-star probably while a stunt man was filming the scene. I liked Roger. Made one the better actors. Daniel Craig of current fame is doing a fine job also.

The 150 he was driving, I think was actually a few different boats. One had an 85 I’m sure. One defo was an inboard and another was a jet drive version too. The magic of film

 

[Sea Rider]

Everybody is talking about HP, speed, props, James Bond but don't see any wot rpm numbers achieved and posted with current prop pitch which is ? and it's imperative to know along the min-max wot rpm range factory stated for that motor. Surely that combo doesn't count with an installed tach to check that out, right ? If wanting top skiing with current combo, must install one yes or yes.

For top skiing need a light boat propped right for the motor to run towards its max wot rpm range for a fast hole shot or a prop that revs around its middle wot rpm range to achieve a slight more top end speed. Will depend entirely on what the skier wants...

Happy Boating​

 

[Tail_Gunner]

I now have a GT, great little ride. With that being said I can't imagine trying to ski behind it. I believe the boats only weights about 700lbs dry. But to your question a 4 blade will give the best bite, with a 70 hp engine...maybe 30ish mph. 18 pitch 17 if there still made. A skeg guard and perhaps some black while your there.

 

[Texasmark]

The 150 he was driving, I think was actually a few different boats. One had an 85 I’m sure. One defo was an inboard and another was a jet drive version too. The magic of film

For the jump, not for all the boats used in the movie!!!!!!!!!

 

[Texasmark]

I now have a GT, great little ride. With that being said I can't imagine trying to ski behind it. I believe the boats only weights about 700lbs dry. But to your question a 4 blade will give the best bite, with a 70 hp engine...maybe 30ish mph. 18 pitch 17 if there still made. A skeg guard and perhaps some black while your there.

More like 15 Pitch, 3 blade if anybody is in the boat besides the driver, Just remember, the prop provides the thrust to push the water astern. The HP provides the torque-RPMs to twist the prop shaft. If you can't twist the prop shaft the prop dimensions are ludicrous.

 

[Tail_Gunner]

More like 15 Pitch, 3 blade if anybody is in the boat besides the driver, Just remember, the prop provides the thrust to push the water astern. The HP provides the torque-RPMs to twist the prop shaft. If you can't twist the prop shaft the prop dimensions are ludicrous.

Your probably right on pitch...perhaps lower trying to pull a skier. Now as to blades.. 4 always win the day...lmao age has a tendency to cement opinions..

 

[Texasmark]

Your probably right on pitch...perhaps lower trying to pull a skier. Now as to blades.. 4 always win the day...lmao age has a tendency to cement opinions..

Ok 4. More surface area to apply thrust.