drive spacers
 

Today I launched my cobra cat for the first time Engines running great and ready to go.I tried to put it up on plane and no good. Props just blowout. I tried everything to get them to grab.I know my X is high [prop shaft center about a 1/2" heigher than bottom of boat], but I thought it would roll over onto plane with a little work but I guess not.I would imagine that I have to get a pair of drive spacers but what size would do the job well? I tell ya between trying to get this boat out of the driveway [can't when neighbors are parked across street] and knowing it's going to be hard on fuel I'm ready to go back to single 26' to 28' boat Would still like it to be a tunnel though. can anybody tell me what size drive spacers I should use? any suggestions. how come my friends cobra with outboards goes on plane and his props are about the same hight? :( :confused: :mad:

What props are you running?
The reason the outboard boat gets on plane is simple. LESS WEIGHT in the ass end.

Thanks for input Tinkerboater, The props are mach sterndrivers 26p Jbrauer is running a twin setup like mine and his drives prop shafts are even with the bottom mine are slightly higher and I don't think he is having any problem getting on plane It does make sense about the weight of the outboards on my friends cobra .I just don't know if I should go for 3" spacers or buy shorter ones. Thanks Keith

Try different props before you start adding spacers, maybe some Bravo 1's.

Which way are the props turning? Try turning them the other way. I was amazed at the difference on my 31' Chris Cat.
Gary

If I have to add spacers do they become a weak link in the drive? I'm also picking up a lot of seaweed in the low water pickups. the holes on the nose cone are even with the bottom so I think their skimming from top of the water. Thanks again for input.

I couldn't get on plane with hydromotive or mirage props. Get bravo props, you'll love the boat then.

Hey Marty, Was hoping you or Jbrauer would respond. Hows your cobra doing? Mine is getting there I still have some finishing to do like the cabin, hatch lift and canvas. I figured I would run it before winter and work out any bugs. I'm going back to the ramp this weekend with a couple sets of props to try. thought I had a set of bravos to try but couldn't get them so I'm trying others But I'm still trying to dig up one more bravo before weekend. I think Jeff is running bravos on his cobra with very good results But I think when we compared drive measurements mine was one inch higher. Wanted to call him but lost his number. I heard that Pete C. of cobraboats thinks that they work well with cleavers. I don't think it will plane but I'll try them [borrowed a pair from my friends cobra . I'll post results. I think that a 2" spacer would make it a trouble free ride. A 3"with out question should do it and if I want I could mill them shorter. Thanks guys

Hey Kieth! Glad to hear you're getting your Cobra wet.

I've tried a lot of different things and think I've got my boat pretty close now. Unfortunately I lost a motor during a poker run in July. I spun a couple rod bearings. It should be back in in a couple weeks.

Definitely get some Bravo 1 props. I've tried 29" Hydromotive Q-IV's, 30" cleavers, 28" Bravos and 31" labbed Bravos. Only the Bravos get on plane relatively easily. The Q-IV's and cleavers sucked out of the hole and weren't as efficient in cruise or top end for me. Want to buy some cleavers??

Plus the labbed 31 Bravo's are the fastest so far at 100 GPS, bouncing on the rev limiters and in the heat of summer. I want to try some labbed 32's next year in cool weather. Maybe 105????

How many HP are your motors?? Try to get a set of Bravos to try. I'll bet 28's or 30's will work. If they're labbed probably 32 or 34's. There are a pair of 34's on eBay right now for $325 for the pair!!! If you're running enough HP per side, they may be the ticket.

After trying to get enough water pressure, I ended up installing 1/2" spacers in my outdrives and using Bob's Machine Shop LWP nose cones. The center of my propshafts are now 1/2" below the tip of the sponsons and it appears to have solved the problems. This process took months of testing different intakes and I'm still not sure if I need the 1/2" spacers. I may take them out next year and try again.

Also, if the water is calm the boat wants to "stick" to the water above 90. Add some chop and it frees right up. I'm going to take ALL of the weight I can out of the bow and see if that helps.

Finally, keep your boat!!! It took me a while to work it out, but I love the results. I'm sure I've got another few MPH to find yet and it runs great as slow as 30 MPH with my wife aboard. The only bad thing is that you and I are on our own with twin I/O Cobra's so it's trial and error.

Here's my office number again 800-645-6083. I'll be out today, but back in on Friday. I have a meeting at 10:30 your time for about an hour, but should be available otherwise. Also, I might have to go to a customer site, but not sure. Either way, give me a call. If I'm out leave you number on my voicemail and I'll call you back when I get in.

Again, glad to hear you boat floats - now we just got to get it to fly!!!!!

Here's a pic from a run we went on to keep you motivated!

Jeff

Hey Jeff, Thanks for info I'll give you a call after the week end. Friday I'm going to english town race track for a swapmeet [looking for vette stuff] Sorry to hear about your engine Hope alls well soon.I had problems with mercs high perf module on one engine not sparking all the time They wanted 1100.00 for a new one and if any coils went bad I wouldn't be able to get them any more so I bought two new style ign systems and engines run great After seeing your exhaust system from pictures you sent I was able to make pipes similar and they work good too. I'll talk to you next week, Thanks again Jeff

Well, this weekend I went to the ramp again with two sets of prop's, One set of cleavers 15x30 and one set of chopper's 14 1/2x28 Couldn't get any bravos to try. The boat still wouldn't plane with the cleavers or even come close to plane, they would brake lose at about 3,000 rpm. I put on the choppers thinking it was a waste of time but did it any way and with a lot of work it finally went on plane I didn't full throttel it but at about 4400rpm's it was moving. It's my first time riding and driving a cat and it's different.I'll have to get some seat time before feeling comfortable with the boat and really getting on it. I marked a center line across my lower unit at the prop shaft and than leveled the boat and leveled the drive and the prop shaft center is1/2" above the bottom of the boat bottom using a straigt edge. do you guys think a 2" spacer would do the trick to get this boat on plane pretty easy? or should I go for a 3" I don't know too much about cats but the ones I've seen are even with the bottom so is a 1 1/2 inch below bottom good enough? need input and thanks, Keith p.s anybody have any spacers that they want to sell 2" to 3"?

You BETTER KEEP that boat!!!,you are so close,just a little more tweekin,and you'll have it right!! Dont give up the CAT!!!,Like they say,If it ain't a cat,its a dog,once you go cat ,you'll never go back,or was that black???:D :D :D sea ya tripps

These props on eBay are probably pretty close to what you'll need. I'm running standard 28's on mine, unless I'm serious and then on go the labbed Bravo's!. ;)

eBay Item #: 2435235525 - Pair of 28" Bravo Props

Keep me posted on your progress.

Jeff

As you go lower with the "X" the slower the boat will be on top end. I know, you need to get on plane first. I have no problems getting on plane with the bravo 30 or 32. When I tried the 34 bravo I would blow out just before breakover. Have friend that has to have his props labed before it will not blow out on takeoff.

I would try 5 blades before I lowered the x

As far as what spacer to use I would not go more that 1" max. The 3" will get you on plane but at what cost in top speed?

Kieth:

1" spacers should put your props in the same location as mine.

Jeff

Hey Tripps, Thanks for the use of your props. All our friends didn't think your wheels would work including myself. but your choppers did the job.I'm going to try to take it to the ramp again this week as long as I can get it out of the drivway. My neighbors are away this week and their cars are off the street so it should be easy. If I do I'll call you. Thanks again Eric. Thanks guys for all the input I was on the phone with Jeff this week and his boat is the same as mine with basically the same. setup. My drives are 1" higher than his so I think I will lower mine 1" and that will stop my nose cones from touching the boat at full down trim than I'll try bravos. Jeff's cobra is working fine with this combo so I think mine should too. Thanks for the help on the phone the other day Jeff. Turbojack, is that your boat in the picture? Nice boat what make is it? and thanks for input . I'll keep you guys posted.

Yes, It's my boat. 2001 26' eliminator daytona w/ walk thru bowrider. My son took picture when he was parasailing.

The reason I said do not go to low is I got off phone last week with guy in San Antonio with same boat as mine & he went from 90 to 103 by raising the x 2". I think he is now 1/2 below the sponsons.

turbojack Wow, That's a big difference in speed. Thanks for info. If I use a 1" spacer thats where my prop shaft center would be, about 1/2" below sponsons. Sound like you have a nice boat. I like bowrider cats. Must be nice to be able to take family and friends out at the same time in a cat. My wife wishes mine was a bowrider or a 4 seater across the back so we could bring friends. My Kids don't care as long as it's fast