Xtb21 question

[bc's xtb21]

My boat is an '89 xtb21 with a 2.4 efi on it. When i'm running in real calm water the boat seems to do kind of a porpoiseing thing about mid sixties, no chine walk just slight up and down of the bow. But when the water has light to moderate chop to it the boat really loosens up and it's a whole lot easier to drive and and rides 100 percent better, it will easily get on up into the eighties. My question is, is this driver error/ inexperience or is this a trait of this hull. Is there something wrong with my setup? When running with chop on the water you could not ask for a boat to drive or handle better but when calm it is a different story. I know a lot of you guys have run a lot more of these hulls than I have so any info wou
D be appreciated. Oh and btw i'm running a a half inch below the pad with a 26p hydromotive tx4 with a JC coned 200 case with 1.87 gears and 10 inches of set back. Thanks guys!

 

[silverbullet02]

I've had the same issue lately with my 2003. I recently brought the motor up just a little and that porpoising seems to have mostly gone away. I had an XTB-21 with 14" setback, and it's set even with the pad. You being 4 inches less, I'm not sure how that would calculate. Might wanna go up a little bit and see what that does for you.

 

[bc's xtb21]

Thanks, silver bullet, what kind of prop wer you running on your xtb and how much hp? Mine seems pretty close to being dialed in but the porpoiseing thing drives me crazy!

 

[K-DAWG XB 2003]

The only time my 2003 does that at around 60 is when it wants some trim.

 

[Dave Hensley]

I had a 1989 XTB and it did the same thing at 55mph. Took it to Darris and he had me add a small lip on I think it was the second strake up on the port side from the pad. He said it was just a speed that the boat needed some hydrodyynamic help to stay on the pad. Thevsmoother the water the worse it was. Fixed mine right up.

 

[JOEALLY]

Mine has a porpoise until I give it more trim (not excessive trim, just a little)

 

[allisonpilot]

My 89 XTB-21 with 8-1/2" of setback 225 PM with SM lower unit realy likes l4-1/2" to 14-5/8" od props.

 

[bc's xtb21]

Thanks for the help guys, I guess the tx4 is a smaller diameter prop. I was originally running a big ear chopper and I don't remember it having that prob. But I sure can drive it easier with a four blade than I could with the chopper. May pull it up to Darris and let him look at the lip and see what he thinks

 

[K-DAWG XB 2003]

Try giving her alittle more trim when it starts porposing before you go drop a lot of cash having Darris look at the bottom. Some props make this worse than other to.

 

[silverbullet02]

Thanks, silver bullet, what kind of prop wer you running on your xtb and how much hp? Mine seems pretty close to being dialed in but the porpoiseing thing drives me crazy!

Stock 150 promax and I was usually running a trophy. Every now and then I had a cut chopper to play with, but mostly a trophy.

 

[suicidealli]

Simple fix just push the pedal down a little further..lol
Most ally's act like that when the motor is really high. My 2002 does it bad 50, when have it high, and ready to run..
The lip on the port/star side is to eliminate the porpoising. When they are gone they really suck to cruise in. Che kit it to see if someone has removed the lips. He put some back on a drag boat for 450.00. I couldnt believe how cheap he did it. It was imbadbob xr. A little less trim might work too...
Just keep messing with it.


Rou

 

[bc's xtb21]

Thanks Roy for the info I'll check on that lip. Also do you know what diameter the quad 4 o/t is? I would still like to try a 28p but I don't know that it wouldn't lug my 2.4 coming out of the hole.