need xr 2002 help!!!! porpoising!!!!

[actmobmar]

had the xr out twice now, boat is a comp model, has a 260 on it w/ 8" of setback, 20" mid, has the lip(.044 in the center),bob's 200 case, propshaft is even w/ the pad, tried a mzco re3 29 p and a 28 et cut done by leading edge ,battery is installed in the back in front of the fuel tank, and boat has the drag plate installed under the jack plate. the boat gets alot of bowrise on takeoff(it does plane off fast), and once up and running (over 65 mph) is fine, but it porpoises at lo speeds(cruise , like 25 mph thru the 50's), no matter where you put the trim. i would like to be able to use this boat for cruising, but the porpoising drives you nuts!! going over waves is difficult(the bow is kitey) any suggestions???? thanks!!!! i was gonna try to go to river ranch w/ it this weekend(s&f event) but at this rate i might be taking my hydrostream

 

[actmobmar]

also, i am using a promax trim section(integral) and the boat does get full negative trim

 

[BGohr]

well here's your problem, porposing is a balance issue, on any boat, and I'll agree with others that you should have the lip on the pad, however, while that will help with your problem it will not correct it.

First of all how much do you weigh?

Second, generally unless you weigh 300lbs. the problem is too much weight in the back. Easiest thing to do is get a couple 25lb bags of shot, run the boat, put one up in front of your feet, run it again, it will get better, put another one up there see if it goes away, and it should, put the battery in the front, if not get a shorter jackplate, or take weight off the back of the boat, do it again. I really think from what you said you just have too much jackplate because you can't trim it down far enough to stop it.

If you have a real comp, that boat doesn't need alot of help to carry the nose, and the lip doesn't matter that much, and I'll agree that the lip should be there, at high speed it lifts the tail and becomes a saftey valve, I will say that my 2002 is the only VBottom that had anything but a straight bottom and all the others ran great without it? 15's didn't have it, my twin GT 20 doesn't have one, and it should, so to each his own on that.

My Comp ran 109MPH in 1000ft. at Kosh, I believe Mr. Scary was there for that one, it was a 84' 2002 Comp, the motor was set back 1", the propshaft was 1/4" below the bottom I weighed 230 and I had 25 in front of the foot rest.

 

[Mr. Scary]

Bill's absolutely right. Anytime I've seen an XR-2002 with a porpoising problem, it's been due to too much rear weight bias. Case in point, when a friend first put his XR2002 together it porpoised. He asked me to drive it....didn't porpoise at all - it drove AWESOME. I weigh about 70 pounds more than he does (he was 140 at the time and I was about 210). We threw a couple of bags under the front of his seat and that cured it.

As far as the lip goes, the more horsepower and the faster you go, the less the lip will increase your performance. It REALLY helps Allisons with 150s and 200s on them - or with heavier engines like OMCs, but if you're running a 260 or a drag, it won't help your performance much either way.

Bill's XRs have always been fast. He straps some killer HP on them and they're setup right. That's a great formula for speed.

 

[actmobmar]

well here's your problem, porposing is a balance issue, on any boat, and I'll agree with others that you should have the lip on the pad, however, while that will help with your problem it will not correct it.

First of all how much do you weigh?

Second, generally unless you weigh 300lbs. the problem is too much weight in the back. Easiest thing to do is get a couple 25lb bags of shot, run the boat, put one up in front of your feet, run it again, it will get better, put another one up there see if it goes away, and it should, put the battery in the front, if not get a shorter jackplate, or take weight off the back of the boat, do it again. I really think from what you said you just have too much jackplate because you can't trim it down far enough to stop it.

If you have a real comp, that boat doesn't need alot of help to carry the nose, and the lip doesn't matter that much, and I'll agree that the lip should be there, at high speed it lifts the tail and becomes a saftey valve, I will say that my 2002 is the only VBottom that had anything but a straight bottom and all the others ran great without it? 15's didn't have it, my twin GT 20 doesn't have one, and it should, so to each his own on that.

My Comp ran 109MPH in 1000ft. at Kosh, I believe Mr. Scary was there for that one, it was a 84' 2002 Comp, the motor was set back 1", the propshaft was 1/4" below the bottom I weighed 230 and I had 25 in front of the foot rest.

i weigh 160 lbs, my friend drew (max 200 on here) drove it, he weighs (i think) 220 lbs, and it still porpoised, he even said about adding weight to the bow, so i'll give it a try in the am, one question, what about gearcases?? i have a sporty on my other boat that has an ally cut skeg and some nose mods, is there any chance of the gearcase doing this?? if there is i could take the 200/bob's case off and try it, thanks everyone for your help, it is needed!!:very happy

 

[BGohr]

don't worry about the gearcase for your balance issue, bring weight and go for a ride, but I'll guess you still have too much set back but go try it

 

[2fast4mom]

Bill is right. Years ago I made a post called "worlds fastest porpoise" about my xr2001 that would progressively leap out of the water worse and worse as speed increased. At 70+ this was a real handful.

I put 50# of shot up in front of my feet. Problem gone. Then I took out 25 lbs of it, problem still gone. I finished up by mounting the battery up front as Darris will tell you he intended.

Balance issue; that nails it.

 

[ImbadBob]

My XR 2001 had the porpoise problem when it was rigged with a 6 inch jackplate with 2 inch spacers added. I changed to an 8 inch Allison plate at the recomendation of Darris and the problem was cured.
Bob

 

[actmobmar]

took it for a ride w/ 60 lbs of sand in front of the gas pedal, what a difference!! thanks everyone!! it still bounces a little, but now i can tuck the bow in and the boat feels much safer, then i talked to darris, he advised against putting weight in, he said to try adding a wedge/lip between the first and second strakes aprox .090 to 1/8" and said that should cure it, has anyone else tried this? he also said the lip on the pad has nothing to do w/ lo speed problems, the lip effects hi speed only

 

[BGohr]

take the battery out of the back move it up front, if it still porposes move the motor closer the boat, moving the motor back will make it worse and you have just verified that. Do you have the jackplate that is able to be shortened?

 

[froggy]

Actmobmar,

Just change out your setback plate! Go from what you have now to a 4" and problem solved. Enough said.

froggy

 

[actmobmar]

not sure, it is a bob's, i'll have to look at it

 

[bruce pitts]

get you a allison foil a small one and put it on see a big change in the boat

 

[actmobmar]

installed the ally drag plate, but i installed the wedges/turndowns between the second and third strakes, problem solved!!! boat drives great, so far it went 105(on friday at river ranch on gps) at 8k rpm spinning a 28 et, then saturday afternoon using a 29 p ally chopper turned it up to 8500 rpm, but the batteries in the gps were dead!!! i guess it was over 110 mph!! gas pedal was between 1/2-3/4 throttle!!!!!!

 

[patches]

Hey Charlie pm me your number please

 

[timber1103]

8500 at 1/2 throttle?? dayamn !! tyner you better move over !!!!!!!!!!!1

 

[actmobmar]

engine doesn't feel like its under any load, kinda wild!! wish i had the gps working for that run, i didn't stay at that speed long though, got up there pretty quickly and slowed down, i have a lot more to learn about driving the boat. pretty sure that friday's run up to 8k rpm was way higher then what the gps said because i got up there quick and then slowed down, what is a good slip percentage to use in the calculator?? i used 4% and the speed was way higher then what was shown

 

[patches]

i use 6.75% for my 28 cut chopper that i river ride with

 

[actmobmar]

thanks eric, inputting your numbers put the speed closer to what the gps said, one thing i did notice is i have alot more torque steer/effort on the steering wheel w/ the ally cut chopper vs the et, and the boat drove nicer w/ the et, i have a 30 et i want to try next, along w/ a modded sportmaster, i have to go out and log the speed/rpm numbers before i switch gearcases so i can see if there is a gain/loss

 

[BGohr]

Get a good 14-26 chopper and take it for a ride, take the drag plate off and balance the boat without it it will be faster, use the drag plate for drag racing