- Boat Type: AT Trimaran
- Length: 20'
- Beam: 88"
- Transom Height: 27"
- Recommended HP: 175 - 235
- Seating: 2 Buckets & Rear Bench
- Approximate Weight: 900 lbs
- Fuel Capacity: 24 Gallons
The HST was released in 1987. Pipkorn, looking to regain the storied racing success of HydroStream's past, took the modified air-entrapment hull design of the XT to the next level; one that would hopefully be able to compete with other strong Mod-VP designs of the day. Extensive research and development went into the bottom design with a goal towards high speeds, exceptional cornering, and stability. Note, however, that the origin of the basic hull design came from Al Stoker's SST - Pipkorn massaged the tunnels and sponsons and developed a new deck. The deck design was an aerodynamic advancement in keeping the bow down at higher speeds. The 1987 hull was a race only version while 1988 introduced the ski version. The race version had a modified cutout in the first 30 inches rearward of the front sponson tips to help aid in turning. The Mod-VP hulls were also very light (apx. 600 - 650 lbs).
If you own an HST that says "HST Skier" on the Coast Guard tag, your boat is no different than the rest. HydroStream sold some with this designation in order to make the boats more insurable and to appeal to a broader market. After all, which boat would your insurance company rather insure: an HST Skier, or an STV River Rocket?
Some of the early HST's suffered quality problems because of the intricate bottom and problems with cracking. They were also very heavy (apx. 1200 lbs) and suffered from weak structural support in the nose area. Quality was inconsistent, and fiberglass and hull layup workmanship was often poor. HST's built from mid 1989 until 1991 were much lighter and better made. This picture shows a 1989 HST with the proper nose reinforcement (picture courtesy of Colin Bodley):
HST's tend to leak in the rear sponson seams and it is a common practice for owners to seal up these seams. Inside, the HST has foam for floatation purposes (Coast Guard approvals), and as with any boat that sees water penetration, the foam will become saturated making for a much heavier and poorer performing boat, and it should be repaired. (Pictures courtesy of Colin Bodley):
The HST is a hull that requires a lot of power to make it work. It takes about 265 HP to get the hull to really start working. After that, every bit of HP produces pretty big gains in MPH. Due to its weight, acceleration is rather poor, but once it reaches speed, it can keep up with or is faster than most Mod-VP hulls. Usually, the HST will get up on pad at apx. 65 - 70 MPH. Setback will help performance - a minimum of 8" is needed. Fortunately, the construction of the HST transom area is extremely strong and will easily handle the added strain of the required setback.
The HST is a great ski boat. Cornering is outstanding for high speed runs as well as just for turning to pick up skiers. They will stay on plane at 17 MPH for knee boarding. The ski pole is usually just a simple one-piece post and is cut through the rear deck - the deck supports it very well.
The interior is not really cramped, but it also is not very spacious when compared to other 20' hulls such as the Vegas. Storage is not very good; mostly just in the sides. Access to the bilge area is very difficult. For that reason, some do not even have a bilge pump. Others do but require a little kid to get back in there to get at it. Some people have cut access hatches in the top of the deck in order to access these rear areas. Gauge setup is extremely good. All the gauges on the passenger side face directly at the driver while the gauges on the driver's side will face you with the aid of angled bezels.
High speed stability? Extremely stable. Driving an HST compared to a Vector is like night and day. The Vector requires an extremely experienced pilot to drive at high speeds while the HST can be driven 85+ MPH by almost anybody. Additional performance modifications can be made by sharpening the step and the tail as much as possible. Sanding a texture to the center pad can help as well. Another modification is to attach 3/16" thick plates angled down slightly under the pods that stick out from the air tunnels. This will not help top end, but will supposedly help acceleration and get the boat on pad at 55 MPH instead of the normal 65 to 70 MPH.
The HST is a great rough water boat and can run well on top of 16" to 20" waves. However, caution is advised with large swells and the errant big wave. Stuffing the bow and damaging the boat is a very real possibility and so the driver must slow down and keep the bow up. At low speeds, the HST rides low in the water and the driver sometimes will need to pick up speed while keeping the bow up in order not to stuff the front.
Recently (2012), Howard Pipkorn and Jeff Baker (HydroStream factory employee, designer, driver back in the day) were both asked: of all the HydroStream models, which was their favorite? The answer from both: HST.