Tarheel

Racerngr1,

I agree with Unsane. Our 98 29 Single ran right at 75 with a 25" QIV Hydro (4 Bladed), HP 500 Carb power, 1.5 Bravo Performance Drive (drilled low water pick-ups by Fountain).

4600 RPM doesn't make any sense unless your gear ratio is different. One thing to consider, Fountain went solely with Bravo props somewhere in there, and they had to mount the drive deeper to get the props to work. That would have given up performance and put you back to 23" or 24" prop.

If you figure it out, I've got a tuned left handed 25" QIV Hydro that was my primary prop for that boat, that's been sitting in its box after being balanced and polished. Let me know if you want it, but it sounds like you may need a different prop.

Racerngr1

How much of a difference is there trimming between numbers. Yesterday when I was running the boat with the Hydromotive prop with 2 people I had 70.1 at 4800 RPM and was trimmed at a 3.5 or so. I just got a performance report from fountain that says that reggie drove my boat trimmed at a #5 with 50 gallons of fuel on board at 75. How much of a difference is there between 1 number on the trim?
James

UNSANE

Fountain raised the drive on a 29 in 02 I believe and that necessitated the change to the Bravo props (so I was told), which provided a little more bow lift. I was testing a 30" Hydro when it was cold that was labbed a bit to calm down the stern lift and it was a pain to plane. Had to be very careful and pull up the tabs to sink the stern as the boat started to get over 15-20 mph and as the prop blew out, it blew out big time! (wish I video'd it) The prop didn't bite until the mid to high 50's. And on 7 cylinders, she ran 80! A Hydro in your case might be the right way to go unless you put a shorty on it.

As far as confirming your gear set, it's in the lower unit I believe. The only way to 100% confirm the gears is to open up the outdrive and count teeth. Know it's a minor pain, but you need to be sure. I'm fairly confident because it's highly improbable you're having only 3% slip. that just doesn't happen.

5 is a lot of trim for a Fountain, even an 01, but those props had a lot of stern lift.

My suggestions are as follows:

1. Confirm your gear set and if they aren't 1.5, change them to there.

2. Also think about if you might want to make any major changes to the powertrain, such as a shorty outdrive or even Procharging the motor, or both. (I know of some that are, should get you 600+hp)

3. Once you have that stuff figured out, get with BBlades for prop testing. Test each wheel at cruise and WOT. Do one setup for summertime "real" use (maybe a 5 blade wheel) that planes better under heavy loads and runs higher cruise speeds. And set up a top speed wheel for hawlinbawlz under light loads. Maybe tack on a smaller wheel for rough water/spare. It will take time and some labbing on the props (maybe.....more so for the WOT wheel).

GOOD LUCK!!! (all it takes is money)

Racerngr1

I just replaced all of the valves and springs in that boat as well as did a MAJOR service. I am replacing the prop shaft tomorrow because the shaft is getting worn/corroded. This is a new to me boat and I have alot to figure out on it yet. My mechanic told me I don't have a Merc prop shaft. I don't plan on doing anything to the engine and/or drive except for making it as turn key as possible. Since I'm replacing the prop shaft I will make sure they verify how many teeth are in the drive. Last and most question is that is this "Prop blow out" that everybody keeps telling me about? Is it like the boat shooting a rooster tail? If it is I'm wondering why my boat running the 24 Hydro doesn't shoot anything out as far as a "rooster tail"

bob_t

Usually prop "blowout" is when the prop loses its bite and rpm's go to the rev limiter and boat speed goes to "zero". When trying to get on plane and the prop blows out, you will think you broke the propshaft! Revs go to the moon, and the boat just "squats" back into the water, at least that is what I have seen with single engine boats. Another time I have seen Hydromotive Q-IV's blow out is when cornering, with a single engine boat. Again, they sort of "fall off plane". Bravo 1 props don't seem to lose their bite when cornering like the Hydro Q-IV's do, from my experience. If I remember correctly, the Hydromotive "X" series props are more like a Bravo 1 prop design.

UNSANE

Listen to my boat as I'm planing out.
http://youtube.com/watch?v=gKbP1jyh-Ak

I'm on a 26 B1 prop here. The more aggressive setup causes the prop to blow out around 20-25 mph, so I'm already going. It's not a big blowout, but I do back off the throttle. Sorry it takes so long, I never floor it and in this instance, and I forgot to hook up my lanyard, so I was fiddling with that.

Yes, Hydro 'X's are more of a round-ear, bow-lifting prop.

Also, based upon your last response, you might want to put 2" shorty on your boat.