Shaft Height

[B.Mac]

1st run yesterday. 18'Hydrostream Vector Jack plate 6" SB running 28 X 14.5 Chopper, LWP, Bobs cone, 150-200 HP 87 Merc. Cant indentify no serial #s dont wanna pull heads right now. lets assume tweaked out 150. My maiden run.......Very hard getting up & out, never felt "blowout" before but believe i'm bolwing out trying to get up & out. Also, moderate turns cause complete loss of prop bite.Stop & start over again. Running shaft heigt now even W/ pad suspect too high. Once out, this thing is a human slingshot, feels like a 2.4 strapped to my back w/ a pizza pan under my butt. 70 MPH @ 4200 RPM & alot more throttle. Any one know at what speed these things blow over? Dropped prop shaft 2" below pad goin back out for another run. Am I on the right track? never been over 70 new frontiers need some advise. Aware of impending chinewalk & need to steer slightly back & forth to keep boat guessing. Am scared silly but then again thats why I do this :) Also have fuel prob see next thread Thanks B.Mac

[Rickracer]

Sounds like the motor was too high, perhaps you need a little more negative trim for holeshot? A Bob's cavitation plate may help out of the hole too. I can get you one if you need it.

[Greg Moss]

That boat is able to turn that prop at split shaft. you not experiencing blow out that happens at high speed. What you are doing is over powering the prop. When it starts to break loose let out of the gas a little and let it bite again. The chine walking will get worse the lower the motor is set because you lower the fulcrum point. Do you have solid mounts and at least dual cable steering? you are going to need it.

[Smitty]

70 mph at 4200 rpm sounds a bit optomistic to me...can I buy your speedo? At 1.1% slip I come up with less than 60

[Greg Moss]

Do you have the exhaust relived The gases coming from the exhaust could be causing the prop to slip. If you want to run the over hub prop you may need to relieve the exhaust to cut down the flow over the prop. This will cause the slipping that you are discribing. What condition is the prop in? it could be that it needs to be worked by a pro. If some face cup is added it may help coming out of the hole letting the prop bite. When you turn are you trimming in?

[AnthonySS]

Dear B. MAC,

Here is a tech responce i just did recently for our PBCC newsletter that might have some helpful tips for for Vector Setup...Hope it Helps

If you have 150-200 (new HP, 1984 or newer) on that Vector, You definitely have the makings of a fast boat. First, before you go fast, make sure you have all the go-fast SAFETY Items are in check.

Foot throttle, Remote Trim (on wheel or floor), Dual Steering, Kill Switch, Solid Mounts a good hi-Impact life vest and wear a Helmut when doing hi-speed runs! Make sure all mechanical items are secure and fasteners are tight.

I recommend the use of an over hub Cleaver prop on your Vector. I still favor those cleavers for the optimum “go fast” and handling. If it is 1983 or older (with 2.0:1 gear reduction), you may be able to swing a 30” pitch, if you make good power around 6-6200 rpm. For newer, a 30 is also possible with strong power and optimum setup! Also try to find a 28 too!

I really like cleavers on sub 18’ Streams. This is due to the Cleavers low rake design (except 32 Cleaver). This is the angle, perpendicular to the hub, that the blade sweeps back, when looking at it straight on from the side. This angle is generally 12-15° on low rake cleavers. The low rake enhances acceleration and helps lift the stern giving your Stream a non-kiting (more friendly) effect on the bow and a more stable angle of attack into the wind.


These sub 18’ really do not need the bow lifting characteristics of hi rake round ear props like choppers. Also steering torque will be less with a low rake and the boat will be easier to drive on your own. Big Blade choppers tend to make the boat roll over on its side. Although I do not have many “hands on” experience with the OMC SST RX, They are also known to be a good all around prop. They are made in both a 27” and 29”. I prefer Cleavers from Quicksilver (Merc).


The new Lighting ET can also be designed with low Rake. I also use one of these for Drags. It has even less rake (10°) than my cleaver and therefore accelerates like a “scalded cat”. I would recommend trying one of these, if you can find someone to loan you one. However, it is NOT a budget prop. Again a 28 –30” pitch would be in order for trial.

In addition, when I suggest that bow lift is not required, I am assuming you are not 400 lb. You may need the bow lifting props if you are a BIG boy. Better yet mount a V6 and some skis on yourself .

As mentioned earlier , to swing this optimum set up, you will require safety items like…Solid Mounts, Good dual steering, Kill Switch, remote trim, foot throttle…and again lets not forget the PFD and Helmut for those WOT runs.

In order to apply all those elements, a good torque tamer on the gear case is also recommended. Then Jack the engine up to Prop shaft centerline even with pad, get the boat up on the Pad…and go for a fly.

I have mentioned the same info a number of times and it does not get more complicated then this on many Streams

SOME RULES OF THUMB…

It takes RPM and Pitch to make speed! You will not get good results until everything is optimized and mechanically fit to the max. to get top RPM and make top speed

I have seen guys get all the right stuff but have scrimped on things like mounts and steering. You will not be able to drive the boat to the max if you cannot first tame it with the aid of Solids and good steering. This also assumes you have a F/T and remote trim so you can have two hands on the wheel at all times

Optimizing your setup means you have get that motor running as perpendicular to the transom as possible. Again, this is were the mounts steering, and, now, a torque tamer comes to your rescue!

I really like the Bob’s drive for this reason. It takes a lot of guesswork out of the “below the water line” stuff. They are good drives for guys on a budget. However, we have seen some skeg failures on 100 mph+ rigs with the modified skegs from Bob’s. The Skeg Failures have generally been on boats that have been run hard, so please get in the habit of checking yours regularly. CLE’s can also get the job done on 85 mph and under streams. Of course, the Premium drive by Today’s Standards is Mercury’s SportMaster (SM) gear case. The SM has the best of everything and requires no modifications to get the job done. Of course there is also a hi-cost associated with this premium unit.

ANOTHER POINT…

When getting acquainted with your new ride, leave all buddies, girlfriends, wives, kids, mother-in-laws and pets on-shore. If you want to scare someone out of supporting your go-fast ride, this is the time it will happen, when you are trying to learn how to drive it! Furthermore, it is always good to have a buddy-boat or someone onshore spotting you in case you “go for a swim”.

ALSO….for more information, I would recommend some articles PBCC have written for reading… go to:

http://www.pbcc.on.ca

…Under the Articles page. We have written some articles on good and not so good experiences with our sport. I think you would find them interesting and entertaining!

We have just scratched the surface here…but I hope this helps some.

I hope this helps some!

Sincerely, Your Brother in Christ

Anthony SS

[Balzy]

you forgot one thing. If you're going to strap on a helmut, make sure you have a helmut restraint system. Don't ever get in a boat and put on a brain bucket without one. You are asking for a broken neck if you ever go for a swim.

Good Gawd Hairy, I gotta follow up and check on you all the time. Just kidding buddy. :D

[AnthonySS]

BALZY<

Youare correct and I don't ever mind a rebuke for the good of our sport.

Unfortuntely I have no restraint yet, I am working on it though!

Sincerely,

AnthonySS

[espen]

Thanks Anthony for a great ansver!
and Balzy for the restraint reminder....where can I get one
and does it fit all helmets?

[Balzy]

and you can send your helmet to them or just buy the kit and install it yourself. Real simple, just pop rivet the D-Rings on. http://www.securityrace.com/ but I don't see it on the website. Give them a call and they will help you out. They were very helpfull.

[Techno]

Everyone else already said the good stuff-except the chine walking steering. You don't yank it back and forth but steer it just before it's needed. Just like riding a bike. if you yanked it B&F you'd fall, same idea. and just like a bike it gets programed in without thinking about it.
And don't back off the throttle severly until you know how it's going to react(try at lower speeds and work up).

My 'used to have' boat cavitated the prop trying to get on plane. I discovered that if I held the throttle at around 2100 it would cavitate just as it was getting on plane but not lose all bite then it would go.
You probaly don't but make sure nothing is mounted in front of the prop like a water pickup. This can cause the prop to cavitate too.