V-King needs more RPM's

I have an 86' V-king YT with an 86' 175 Merc, 7" setback on a L&S plate, CLE LU running about 1.5" below the pad with 15psi water pressure at WOT.    When I bought the boat last year it had a 14x29" Hoss Triton and will run 76 GPS @ 6000rpm's.  I recently purchased a 26" Hill Chopper to try and get the RPM's up but the boat runs EXACTLY the same speed and RPM's.  How can this be?  And why can't I get this motor to turn more than 6000 rpm's?  I just had the Hoss worked by Dave and it's a true 29" he said.

The motor has 138 lb compression on all 6 and oil injection is installed and runs great.  Is this all I should expect from this setup or is there something that I'm missing.  Is this motor worth modifying, (i.e. heads and tuner, strip oil injection) or should I just "bite the bullet" and upgrade to more Cubic Inches?  I'd like to see low 80's, is it possible with this setup? 



The reason for the RPM staying at 6000 is because the 26 is really a 28 at the peak and it probably has a ton of cup. Most Hill choppers are this way. This is a good example of why the RPM x gear ratio x pitch = speed theories don't work. Unless you know the true pitch of the prop and what part of the blade is doing the work, you can't make a true calculation of prop slip. I've worked lots of Hill Choppers and they can be made to work excellent, so don't be too depressed. The Hoss is showing good numbers. Here is my recommendation: Have Bob's put a cone on the CLE. This will put you over 80 mph in itself. Just adding power will take over 10 hp to gain just 1 mph, so do the case. It will allow you to take the boat to new levels of set-up. Expect to lose RPM and gain speed.

The efficiency will be better so you can try running slightly higher to get more speed and RPM with it. I would expect around 84 mph with the set-up optimized. Try running 25' of timing at W.O.T. on the engine. Slightly retarded timing was one of the differences between the 200 and the 175. Trust me, the gearcase is where the speed is, as the CLE works only when 3" higher than you are now and that just won't work on the V-King/175.




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.

Mark C.


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