Best Lower Unit for Vector & HST

Randy,
Our family now has 2 Hydrostreams : a 1990 HST with 2.4 Merc bridgeport ( my brothers) and a 1981 Vector with 1981 Merc 225 ( My boat).
I have two questions.
1. What would be the best gearcase for both boats? : At the moment they both have CLE's on them. My brothers CLE needs to be replaced (broken skeg) so we were thinking of putting my CLE with torque tab on his HST and getting a Bobs coned unit for my Vector. Does this sound like a good idea?
2. The HST is new to us. Do you have any tips on proper setup? ie propshaft height, setback and best all around prop? Currently has 9 inches of setback, running an old 28" chopper. Only ran it one weekend so far and saw 80+ at around 6700 rpm.

Thanks for the help
Brent

 

Brent,

Answer to question 1:  Both boats would run better with a Bobs coned gearcase.  I have tried CLE and Sportmaster cases, but none are as fast as the Bobs coned.  I would suggest sending the CLE out and have it converted.  You will be happy with the results.   

Answer to question 2:  The HST seems to like about 12 inches of setback.  Less and it will not carry weight.  More and you compromise the top end.  I have run the engine at 1/2 inch below the bottom with the most success.  We have run in excess of 100 mph at this height.  The 28 chopper is a good choice as is any good round ear overhub.  You should shoot for 7,000+ rpm to get into the 90's.  If your motor is a bridgeport EFI, and has the A7 ECU, it will be limited at 6900 - 7000 rpm.  You will need the A13 to turn over 7000.   

Try a few of these and you should get into the 90's.  You may need a 30 inch prop if you chose to keep the A7 box.  Good luck on your setup. 

Randy

 

 

Please submit whatever questions you have to IHRTechTalk@yahoo.com.  All questions and answers selected will be displayed on this page as they come in.  Note: though all boaters are welcome, priority may be given to I.H.R. members.  Randy can not be held responsible for any advice given.  Though his information and expertise is second to none, he has no control over what you do with your boat.  It is up to you to boat safely and act responsibly, and his advice is only to be used as a guidance for your high performance boat/motor of which you are the one responsible for the risks involved.

Thanks,
Mark C.

 

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