Swapping Drives to Improve Porpoise
 

I installed new 350EFIs with new counterrotating Alpa drives in my '87 Stinger 260 a few years back. The reliability of this settup has been outstanding! Top speed is 59mph GPS with full fuel! Like most (all) other Stingers, the porpoise is still very much there if I try to bring out the drives more than a couple of bumps of trim. I read somewhere that owners of Baja's and other hulls with the porpoise tendency have been able to solve their problems back rigging the drives to turn the props in towards each other instead of the conventional outward rotation. Has anyone tried running the drives turning inward? Did it help the problem? How much of a hit did it have on top speed?

Re: Swapping Drives to Improve Porpoise
 

Good idea! I would be interested to see if that works. I have SBC with OMC Cobras that counter rotate outwards and I too have the same problem. Someone on here was saying though that it depends on where the reverse gearing is done. I'll wait and see what the experts say.

Re: Swapping Drives to Improve Porpoise
 

Exactly. Some boats (my guess is not high performance mostly) have reverse direction mills. Most have one drive that rotates in the opposite direction as the other. Lucky Volvo owners can switch the directions of the drives without taking them off and switch props.

I'm no expert. But the in vs. out rotation would effect the stern lift differently. I think that spinning in creates more lift. Somebody correct me if I am wrong.

Since the stern vs. bow balance relationship is the actual culprit in porpoising, theoretically it MUST change the balance relationship between the stern and the bow, and therefore MUST change the behavior of the hull when you trim out.

You have tried them spinning out. Maybe spinning in is the way to go.

Damn I wish I had new drives and power. :D

People who drive Stinger 260s are the coolest people in the world. Especially 1987. :D

I would love to hear about it if you try it.
Good luck.

Re: Swapping Drives to Improve Porpoise
 

actually its the "85" guys that are the coolest :drink:


and so far the fastest too :D


by the way Jon ya gonna be out this weekend. :cool:

Re: Swapping Drives to Improve Porpoise
 

oh . . .i may be the coolest an the fastest but im definetly not the brightest . . thats Packinair driving MY boat :eek: :rolleyes:.



not the one with her top off :rolleyes:

Re: Swapping Drives to Improve Porpoise
 

I have the telethon on Sunday.

I don't have my boat back.

But I thought about driving (yes, I know) the truck up to Clamdiggers to see who I could see.

Re: Swapping Drives to Improve Porpoise
 

I will give you fastest.

But coolest?
I don't know. You might not have enough purple on your boat.
:D

Re: Swapping Drives to Improve Porpoise
 

With alpha drives you'll have to switch drives,then you'll have to switch the way the cables to your shifters are mounted.you could just switch the drives,leave the cables as is but they will work backwards,forward will be reverse,etc.As for the cobra drives,I thought I read on this board that they are like bravo drives.That is that they are a cone clutch type drive and will hold up in either direction.In that case you would just have to switch props and change the shift cables at the helm.I'd check on that before trying though[legal disclaimer].By the way,does anyone know the weight of a 260 stinger with smallblocks and alpha's.I have an 87 I'm building motors for,hope to be in water soon.

Re: Swapping Drives to Improve Porpoise
 

cool . . .grab me a tote bag :D

Re: Swapping Drives to Improve Porpoise
 

magnum, i was wondering the weight of these things as well. i thought i heard #6500 but that seems kinda high, course this thing is a tank though :rolleyes: :D

what are you building for motors? any pics?

Re: Swapping Drives to Improve Porpoise
 

I heard 6000 plus, too.

That would explain my WOT speed. :D

Re: Swapping Drives to Improve Porpoise
 

I don't have a tote bag, but I have a tote board. :D

Re: Swapping Drives to Improve Porpoise
 

jeezsus . . .i took my boat down to the local river front friday night with a full fuel load and 6 people on board and my tabs decided to stop working. water was fairly smooth and my frikn boat just porpoised like crazy, worse than ever with that load.. anybody got a spare pump for a bennett system? would swiching to a 280 K plane help? :rolleyes:

Re: Swapping Drives to Improve Porpoise
 

I have some pics of my boat when I bought it,I need to scan them then figure out how to post them.The engines I built are 355's with hydraulic roller cams,sr torquer heads,performer rpm intakes with quadrajet carbs.Motors are in the boat,one's running the other should be soon,just to many other projects that are more important.I ran a desktop dyno program on them and it came up with 375hp but I think 350 is more realistic since I have stock exhaust manifolds.As for the 280 k-planes are concerned I can't answer but I'm planning on using them.Ihave a set that needs alot of work,no rams or thru hull fittings just the plates if you're interested.

Re: Swapping Drives to Improve Porpoise
 

It probably always porpoised like that.... except that you have never seen smooth water before. :D

Re: Swapping Drives to Improve Porpoise
 

I think I read in a brochure for the '87 that the basic hull is somewhere around 3800lbs. Using that for the basis, 900 lbs apiece for each engine/drive package, and 750 lbs for the 126 gallons on gas, and I drop into the water at about 6100 lbs, which sounds like what y'all are saying.

Re: Swapping Drives to Improve Porpoise
 

Mine just became a huge freaking project so I am considering Volvo drives.

Re: Swapping Drives to Improve Porpoise
 

Magnum,


You should be lookin' at almost 80mph with 375 h/p ea eh......Those sound like great engines....do you have pics? Also who's thru transom exh. are you using?


D-

Re: Swapping Drives to Improve Porpoise
 

Boosted,the exhaust has been the biggest pain of this project so far.Originally the boat had thru the drive stock exhaust.I bought some corsa transom mount mufflers and wanted to install them below the swim platform,after measuring everything out I started drilling the 4" holes in the transom when I discoverd on the last hole that the steering ram inside the boat was in the way.Now I have 6" risers added between the manifold and elbows wich puts the outlets in the swim platform.Had to cut 8" holes in the transom and 4" holes in the platform.Right now I'm making some trim rings to clean up the install then I just have to wire and plumb the port motor then hopefully we'll get it wet.If it does'nt rain this weekend Ill try to get some pics,have another project that's more important right now though.80 would be sweet but I think I'll be closer to GlassDave's speeds.


Thanks for the interest,Magnum

Re: Swapping Drives to Improve Porpoise
 

magnum i had the same problem. i started with the one at the steering ram and mounted it as low as i could had to do all my drilling from the inside and careful measurments. i used straight cut tips and salsbury external flappers. the top of exhaust tips are just barely above the line of the platform deck but there is enough room so that ist not a problem with the exhaust flow. with everything exiting under the platform this thing sounds like it has 1000 Sterlings in it (Fund can back me up on that :D ) has a VERY deep rumble. sounds great and i also have silent choice on it for those late nites get'n back to the boat club :drink: :drink:

with a pair of 375's an the right props you should see mid 60's pretty easy. :cool:

Re: Swapping Drives to Improve Porpoise
 

I'm one of the baja guys that tried the props turning in. On my 320 it made it porpoise much worse. IT Definately lifts the bow more but I couldn't hardly trim it up at all without th boat getting real squirrely. Supposedly turning in will give you a little more speed but in my case it didn't cause I never could use any trim. It seems that it depends on the boat though I have heard some guys that like the props turning in.

Re: Swapping Drives to Improve Porpoise
 

I thought about dropping the one hole down also but the mufflers are almost 8" in diameter,would of hit the gimble housing.I wish that would of worked,I'd probably be on the water now!I have to fix my truck first,boke the timing chain and apparently bent some valves also.tearing it down the rest of the way tommorw.0 lbs compression on #3 cylinder hope the piston doesn't have a hole also.

Hi, fyi - I've got a Stinger 260 and new counter rotating Alpha 1's with 4 blade Mer Rev4 props. Have swapped to turn inwards and it certainly lifts the stern up and does appear so far to improve porposing. I have noticed in rougher conditions with legs trimmed up slight cavitation and chine walk at higher speeds (I think that's what it's called when stern feels like it's jumping a bit across the water?). But everything down solves this, just loses speed slightly. Overall my top speed may have dropped by a few mph from 59 down to 56 but that's not really a concern for me (it did actually go up initially when I added counter rotating and 4 blade props from around 55mph). I've got the standard 260HP mercs. It also gets up on plane faster and handles rougher weather better. I think it's getting used to how i best trim everything with this newconfiguration - I've fouind that tabs down and drives trimmed up gets best results at higher speeds