QUESTION:

Many people query as to whether it is possible to switch their boat from a prop to a jet.

QUESTION:

A lot of people who are interested in buying jet boats frequently ask me questions about the bottom degrees on river boats. Often they are under the impression that the shallower the bottom degree the less water you need to travel in.

This may be true in some cases, however, the shallower the degree the more the boat will slide causing less control. It also has the disadvantage of bouncing your chiclets (teeth) out in rough water. If you are interested in buying a boat you have to first ask yourself what you will be using the boat for and where you will be using it. For example,

A 6 degree bottom will not give you a comfortable ride if you are going to be spending much time cruising through lakes. An 18 degree bottom allows the boat to cut through the waves instead of bouncing off the top of them. But if you are intending to run either lakes or rivers or both, then the most common choices are between 8 and 14 degrees.

QUESTION:

Recently we were approached by a guy who owns a 23' welded aluminum jet boat with a 10 degree bottom. He has a 383 Chevrolet engine with a 3 stage Kodiak jet. He was running 3 coarse impellers with a posi-flow nozzle. He complained that the jet would spin out from a dead stop and from a running start.. After doing some digging we discovered that quite simply he had exceeded the horse power range of the jet. According to the Kodiak specifications for these jets, they work at optimum on boats that are 21' or less. So the length of the boat + the horsepower of that engine = a situation that exceeded the intended use of that particular jet drive. It spins out because it can't get enough water into the intake.

QUESTION:

Here's another common question. What is the difference between the Kodiak 3-stage and the American Turbine single-stage. Well this is a fully loaded question. There are those who swear by the Kodiak 3-stage and although we would never knock it, lets not forget about the American Turbine. Here's why...

This is the performance data for the American Turbine Jet. In tests done by American Turbine here's what they found according to American Turbine Performance Test Data:

• More efficient impeller design that flows more water with higher pressure
• New, improved suction-to-impeller flow line which helps feed water to the impeller with a more balanced flow.
• Shouldered wear ring for reduced cavitation.
• More precise tolerances on parts achieved with computerized machining.
• Enhanced bowl flow characteristics.
• Optional Hi-Performance intake with shoe and rideplate fitted for maximum performance.

The Kodiak 3-stage Jet features:

• Stainless steel impellers
• Strong one-piece reverse deflector
• Posi-flow nozzle

(Kodiak publication)

• The multiple impeller units move a greater volume of water under increased pressure. This means more weight can be carried in the boat or the boat can be larger
• True axial flow jet design for instant acceleration and maximum fuel economy.

(Marine Jet Drive published by Seloc publications)

Here's what we've found:

We've worked with boats with both types of jets. We've found that the performance and fuel efficiency in the American Turbine is outstanding. The low speed maneuvering on the American Turbine is not as good as the Kodiak. Both styles will push water back into the intake while in reverse. The American Turbine has a larger horsepower rating and it's simple design makes it easier and cheaper to repair. The 3-stage pump has more parts to it and is a lot more expensive to fix. Here's why: The 3-stage has three stainless steel impellers in it. Each impeller costs $700 to replace whereas an impeller for a single stage is only $300 and you only need 1.

QUESTION:

What's the difference between axial flow(ie.) and mixed flow(ie.)?

Taken form Seloc Publications "Marine Jet Drive" Manual.

Water in an axial pump moves on a single axis, thus the word "axial". In simple terms, water is ingested and discharged in roughly a straight line. The mixed flow pump produces the greatest amount of actual water pressure. A mixed flow system utilizes the best features of both the axial flow and centrifugal pumps, namely a great amount of water discharged at a higher velocity. Therefore, many consider it to be the most efficient for boat drive application. The water flow is not in a definite straight line, however it could be considered close. Also, the impeller is rotating, as in a centrifugal pump, but the water is discharged out the rear instead of on the perimeter of the pump body. The vanes in the pump bowl have much to do with redirecting the flow in the desired direction.