STV "hopping" problem,HELP!!

[Desperado]

Just got my STV River Racer rigged and in the water today for the first time(2003 15" 280 Race Offshore) and it runs like a "Scalded Cat"!,But,it hops badly between 6-7k and could not get it to stop by trimming in or out.If I backed out and started over and pushed it hard,it didn't happen.So,is this a STV trait or am I doing something wrong?Thanks guys!

[tunnelboat17]

:rolleyes: What is the heightof the motor, any setback? Prop type? Which gearcase? Gas tank full+in back against transom? Unusual for STVs???:confused:

[ProComp]

What kind of prop are you running?
Also, what height?
There are RR owners you can better help you out but
usually you trim up through the bounce to air out the boat and then trim back down for your speed run. If the prop has too much lift, it can be difficult to get the boat to settle down.

ProComp

[Desperado]

Propshaft is half inch above bottom,8" setback,26 Yam,stock gearcase,15 gals of gas in the tank against transom.I was just told by 2 other STV owners via email that this is normal for this boat as air is packing and lifting back end and to just power through it.Yours does not do this?Thanks

[tunnelboat17]

I had an 89 MOD-VP with driver capsule that was a tame as a kitten!! STVHelm, the boat in S+F video gave me a ride the day the video was shot+not a hop out of it!!!! But maybe the RR is little different bottom,center of balance,aerodynamics-the air travelling over the deck +into the cockpit and out over the transom + motor at 6-7k, which is when the aerodynamics begin to have effect on the boat? I've always had the best results with a Lab cleaver- but the Yammi has gotten raves from people I know. A little bit of hop can be fun! A BIG NASTY HOP is handful sometimes. 24 Skater hopping is fixed with a tunneltab- mixed reviews on this forum. Keep gathering info+try little changes 1 at a time and you'll probably get it settled down to a nice passenger comfortable ride! Good Luck . :cool:

[stvhelm]

Somewhere around 80 is a sensitive spot. Keep a little positve trim before you get there and it should hang. If it dont its probably cause your prop has too much bite and it's holding the back off the boat down. Try running a cleaver and it should stop. I had the same problem when I first got mine but I quiclky figured out how to avoid it. just practice and play with different trim settings while slowly approaching 80. If you blow past it you'll never have a problem.:cool:

[W. Tripp]

The Porpoising happens when the air in the tunnels is on the verge of lifting the outside sponsons free from the water. Getting the setup right on the boat will reduce this dramatically. The transom of the boat will lift as water pressure builds, if the bow is too low, the nose will hop trying to lift, and dump the air pressure each time it hops. The STV wants to run at 10-15 degrees above the surface of the water. Your setup and driving style need to compliment this angle.

If you don't have a good mechanical trim guage, get one. set the guage up so that the propshaft is at neutral trim at about 3/4 of the range of the guage. The boat will run best top speeds with just a touch of positive trim. When the boat starts to porpoise, give the boat a touch of trim to help lift it.

The propshaft sounds a bit too low for 8 inches of setback. I would try moving it up in 1/8 inch increments. You SHOULD find that best acceleration and driving happen with the propshaft 3/4 to 7/8 inch above pad, with very little or no loss of top speed compared to higher settings, but many run their STV's higher than this.

The 26 Yamaha is a good prop, but the River Rocket generally likes a Mazco RE3 best. The Merc Lightning ET is also a good choice, but tends to make the bow "hunt around" a bit at high speed on a light RR. AN "ET cut" Chopper also works well. Cleavers drive great (especially at high speeds), but don't accelerate well. It takes a bit for the boat to catch up with the prop speed.

My .02, but I hope it helps,

[Desperado]

Thanks guys! I am now headed for the river to put in some more seat time and work on getting the kinks out.I d plan on trying some of your tips(props,height,etc)Its good to know now what this is all about and that it is a characteristic of the boat,notjust the driver(Me!) Thanks ro all!

[stvneil]

i have a 95 rr with a 260,4" setback about 1" above the bottom of the hull. my pin is in the third hole from the transom. when hitting it from a dead stop, i give the up trim two little bumps. no problems at all. i run a 26 yamaha, 27 hoss triton, both at 9000+ rpm's. when running at cruising speeds and run thru 6-7000 rpm's i do get some hop, but i trim thru it and then trim back down. don't underestimate the mazco re. very little steering torque and very smooth.
neil

[Raceman]

I've run several different configurations on my STV's and the mid range "STV hop" becomes worse with setback. I've only got 5 inches plus 15" midsections on both my boats now and it's drastically more than it was with 20 inch mids mounted directly to the transom. The reason that I mention the 15" mids is that they have 2" of extra setback built into the swivel bracket over their 20" counterparts, so you're essentially adding 10" to what you would've had with a longshaft engine bolted directly to the transom.

In any case, it can be overcome with seat time and set up, but I wouldn't want that much setback.

[Desperado]

JUST SOLD IT!Now I need to sell the 2003 280 15" "race version",first 13k take s it,less than 5 hrs!!

[Raceman]

Why don't you list it in the Engines For Sale Forum? It'll get more exposure there.