Based on Ben Robertson's assesment the harmonics are prop cavitation related. If you tuck the drives in it goes away. We don't believe it's the driveline itself since trimming in or out doesn't affect any of the rotating driveline between the tranny & transom / drive.

Mercury props liked pos trim but the Herings no, much more than + 1 above neutral & it feels real flighty. The props have such a bite carrying the bow already no need for trim. I can run a mile or 2 WOT trimming up & down but don't gain anything. Conditions have primarily flat & sticky since Labor Day & the lake being deserted.

Looking like a tunnel ext or tab. Soon TBD!

Would #6 style aeration tubes be of any help since its prop related at speed? Why do all race boats have them?

Don't know that answer zero exp there but I do know that I'm not spinning big enough wheels to require tubes based on what their intended for. I can get on plane w/o tabs or tucking the drives in w/ ease.

Wow

Tim,

I thought you already ran 146 w/ that boat & 35 or 36 pitch. Can't be very good getting on plane w/ fuel & people though.

You are speaking of the 38 Titanium props correct?

Look aggressive & cool but I need to run them one more time to determine whether they are worth anything. I felt as if they made the boat flighty, edgy above 100. To be cont'd...

Took advantage of what will more than likely & regretably be the last hurrah for my 2010 boating season.

The weather was great, sunny, crisp & cool, barely another boat on the lake, flat w/ a slight ripple. Bolted on the Hering 39's & posted a new personal best for me & my 30 Skater of 137mph. While I realize that I won't be able to back that up mid summer w/ 4 on board & tank of fuel I was still impressed w/ the fact that a boat that gained 250+ lbs thru the drive upgrade much of which is rotating weight including transmissions & 1.25" larger diameter propellers was able to exceed it's previous top speed of 135mph attained by me as well as documented during a 2008 PB Mag test.

While I'm still looking to minimize the hop & have a few other things left to test in the future I believe this Ilmor Indy Drive upgrade project has proven to be a successful one from both a reliability & performance standpoint.

Many questioned the 1.50 drive ratio choice (including me, several times) but in the end I've gained durability, reliability & excellent acceleration without giving up anything on top. If the opportunity presents itself to test a set of 1.39 drives I'd love to do so just to see what type of #'s I could post but in the end I don't see myself sticking w/ that setup.

I've learned alot throughout this project thanks to the time, effort & expertise of many others who have been more than willing to share their experiences. The one that has captured my attention the most is what a difference hull, driveline & prop efficiency make. If I were a betting man I would have been a losing man based on the fact that in my experience (w/ cars, boats & motorcycles) adding static weight & rotating weight to a vehicle w/ the same H.P. would never yield more speed.

I'd like to extend a specials THANKS to all that contributed to the success of this project especially...............

ILMOR High Performance
Douglas Marine / Skater
Hering Propellers
BAR Performance Marine
Performance Images
TCM
and last but not least my friends & fellow performance boaters!!!

To be continued........................

:ernaehrung004: