jet propulsion setup

blueovalspecial

Recruit
Joined
Nov 24, 2002
Messages
1
I am trying to help out a friend of mine with his newly acquired Zodiac. He does a lot of river boating (several shallow areas), so he uses a small jet setup. It works great on the river, but when he gets into open water and opens up the throttle the rear of the boat just sinks and the front raises to the point that the drag almost overcomes the engine. So my question is, is this normal and if not, where should the suction for the jet be set up (relative to the keel) for the boat to function properly. It's approximately a 10' Zodiac and he has a 50 hp jet propulsion setup on it. He has been told that the suction should be in line with the keel, but we have our doubts. Thanks in advance for the help.
 

punt

Cadet
Joined
Nov 21, 2002
Messages
10
Re: jet propulsion setup

Are those numbers corrct, a 10 foot inflateble with a 50 horse jet¿<br />I'd thin a motor that big would sink that boat just from it's weight.
 

Terry H

Lieutenant Commander
Joined
Sep 25, 2001
Messages
1,862
Re: jet propulsion setup

Blue...if your friend wants to get on plane fast with a jet pump he first needs to start the forward motion slowly then stomp the accelerator. Standing still the intake sucks a huge amount of water from below the motor driving it downward...<br />once in motion you can feed it with water from under the hull. Sounds like a sweet setup, just need to get used to the way it handles...<br />just a Thought
 

Skinnywater

Commander
Joined
Mar 7, 2002
Messages
2,065
Re: jet propulsion setup

In addition to Thought101's points.<br /><br />The forward edge of the pump intake should be flush with the bottom of the boat.<br />If it cavitates it is to high. If you get excessive splash back or poor performance you're to low. Being to high or low is usually within 1/2 in of each other. Go as high as you can without cavitating.<br /><br />Also keep in mind that the keel and bottom design can introduce/direct air into the jet, causing inefficientcies.
 
D

DJ

Guest
Re: jet propulsion setup

blueovalspecial,<br /><br />Is the inflateable you're using a hard or soft bottom?<br /><br />If it's soft, the dynamics of the water flow change dramatically with water conditions.
 
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