Different answer to V-Drive tech

[V-Drive Tom]

Please reference Hot Boat magazine, V-Drive TECH April 2002
First the man has a Sanger runnerbottom hull.(Most are heavy All are Large) a 427 chevy engine and 1.22 gears with an 11x16 2-blade.
The 427 is overloaded with gear overdrive. The second you go past the power capability of your engine even by 3 to 5% the boat will become Lazy...(this holds true with a good steel prop not brass. Rule changes a little if you have a Blower.)
More prop dia. and blade area are effective mostly for take-off. It does not translate into more speed.....
The reason he feels the "set" is nice at speed is probably because the boat is glued in the water,not hopping or doing anything to scar him.
AGAIN the combiation is overloaded!
Running the numbers with a 15% gear in the v-drive. The RPM will increase by at least 500. 7000 rpm with 20% slip WILL see about 96 mph.
NOW the boat will be more responsive quicker and faster.
Yes the wing should come off for a try.If its adjusted wrong it can only hurt.Its not going to help the boat for anything but to look Moo Bitchin... This adresses only the motor to gear and prop combination. Cav plate adjustment and how he is driving the boat would be next.This only touches the surfice because I can go only by the info given to Mr.Wilkes in the magazine. THANK YOU FOR YOUR SUPPORT V-DRIVE HEADS! TOM BENTLEY MENKENS V-DRIVES (530-885-0531) MOO answers on other questions soon! Lets talk about it because this v-drive forum needs more ACTION..!

[Jetboatguru]

Tom, I agree with you that the motor and boat are way overgeared. A 427 motor making 800 hp is overgeared with 22's if he is running the propeller you described. The wing on a boat with that kind of performance is just as you say, to look way cool. 15's in the box is a good call.
I have a question V-drive Tom, I just put a set of 18's in my V-drive and it seemed that there was very little backlash in the gears but there was some.
At idle and low rpm in gear, there is some chattering going on. I know there is plenty of oil and when I get on the gas a little it goes away. Is this normal?
Thanks.

[Costello]

Hey Tom,
I did not get my issue yet, but reading what you posted here, if the guy changed pitch to say 15 would that not be the same net result as a gear change? How does dropping pitch equate to dropping gear? For example does a 1.22 and 16 pitch equate to a 1.18 and 15 pitch? Thanks for insights, Gary

[V-Drive Tom]

GURU..even 7or8 thousandths (that would be a minimum)is ok if the spacers are holding the gears properly. the rattling in the 5 mph zone is going to happen. one thing to watch out for is excessive wear on the top shaft spline. the shaft is shofter than the gear and the weight of the gear pushes into the spline,making for more rattle. I did not see anything about 800hp coming out of the guys 427. It would about that much to pull a 15 or 18 gear with a good prop,and be a stronge runner. GURU..WATCHTHELIGHTS!!

[V-Drive Tom]

COSTELLO..Some would say that 1# in pitch is worth 9% in gear. I dont think thats realistic. Raising or lowering gear ratio by 6 to 9% is a more affective than one in pitch. BUT because ten props laying on a table, all stamped 11 1/4 x 16 can act so differently(because of pitch progression,blade area,and blade rake)you need to adjust gear to that prop. A lot of the 16 pitch props can be more than low horsepower want to pull. If the prop is mean, lower the gear. If your pulling it to easily, put more gear in it...I have to go take a gearbox apart...talk to you LATER!

[Costello]

That makes sense, tune your gear ratio to a prop that makes the boat happy as far as bite on the leave, lift etc. instead of trying to find a prop to match a gear set. Obviously that's the more economical solution too! Thanks for the 6-9% rule of thumb too as that's what I was actually thinking of initially.

[Thunderbutt]

Tom, I have a Spectra-20, it has 9 persent over in a Champion v-drive. I talked to you abouy 7 years ago about putting in taller gears. At that time you didn't know anybody that made gears for the champion. I have found somebody that does. Am I waisting my time and money on this heavy boat? The motor is a 468. With a 12.5X15 prop it pulls 6200 RPM, with a 13X15 it pulls 5900.

[Jetboatguru]

Thanks for the info on the gear lash Tom

[shirkey4750]

While this topic is going,I have a 18' Sanger drag hydro. running a 454 .030 over 10 1/2:1 forged pistons 119 cc oval port heads,tunnelram with 600 holleys, cam is a comp .244 .254-.570 .575 110 deg. centerline. 1:22 gears, 11 1/2 x 17 cleaver at 5700rpm. What would be the ideal set up for this application? Runs 83 on rader. Would rather change gearing than prop.

[V-Drive Tom]

Shirkey4750--You should try the 15 or 18 gears because you need to increase your rpm. Your engine set up the way it is with mild compression and mild cam will still make power up to about 6300 in my opinion. You'll be much happier with how the boat leaves.
Need more compression, need more cam, bigger heads, more carb, more everything! I know $$$!! Tom

[V-Drive Tom]

Thunderbutt--Yes sir I know who has the Champion v-drive parts also. But, 15% ratio is not available to my knowledge, or even 12's. The Spectra 20 that you have is a great boat!! If you really feel you want to go faster in that boat, then a new v-drive or a custom-made gear set and blower or turbo would give it that kick. I think you are referring to three-blade props. A large two-blade would give you about 5 to 7 mph and more rpm. But, if the boat is being used for hauling people and pulling kids on water toys, then you wouldn't like that because of the slight vibration, and it won't pull as hard from low speeds. Tom