Are Imco Extremes Junk ?
 

I have a baja 272 with a 540 with an 8-71 blower and supper chiller. I started out with an imco extreme 1.36 ratio and it lasted a couple months and then broke the upper shaft in it. I switched to an imco extreme with 1.50 ratio and broke it the first time out. ANY SUGGESTIONS ON WHAT TO TRY NEXT ?

How much power are you making and what prop are you trying to turn? I have the same boat and have ran big power in it for years (my blown 540 made 944hp/967 ft lbs of tq 3 years ago) and am now running over a 1000 hp in it ( haven't really started beating on it super hard yet with latest motor set-up). I usually run a 30 labbed bravo up to 6000 and run 90 mph,run a 32 labbed at 5700-5800 when running light and see 92.5 to 92.8 (gps) and plan on mid 90's to low 100's with the new power but haven't been there yet. I was chewing up lower 1.50 gear sets every 10-15 hours but have cured that,have sheared off 1 max worx billet prop shaft but it had over 200 hours and I was trying to run a 5 blade maximus prop. Sheared off a max worx billet vert shaft a few years ago driving like a retard torque loading the boat repeatedly from a slow rolling start but for the most part my Max machine worx drive has the same upper and most the same lower parts in it that I bought years ago. Give us some more info and some dyno and speed gps numbers if you have them,I can tell you I never broke a prop shaft ever even with all the tq my motor makes until I bolted on a 5 blade prop then it only took a few (about 10) passes and I sheared one right off,I stay away from 5 blade props,Smitty

Smitty every post of yours i read mentions this 5 blade phobia.Man your scaring me.I just unpacked my new Maximus.Makes my XR look like an alpha.You'd swear it has twice the surface area of my 34 Bravo.Are they really that bad?

Smitty´s right, you know. I´ve got two Maximus´s here. A labbed and an unlabbed 26", and although the midrange pull is amazing and the labbed prop comes pretty close on the 80 mile top end of the Bravo, it feels like the there is a giant octopus hanging on to the back of the boat and the motor is trying its best to break free.
Its an XR killer for sure. I´ve only run the five blade on one poker run and two test sessions, but will stick to 4 blades in future.

Coincidentally, both my XR and the Imco extreme on my buddy´s Aero Tek have died in the last tthree weeks. Both have around 120 hours on them.
The Imco has thrown a UJ out of the side, when running at 90 mph.

The XR suddenly spilled all its drive oil into the belows and on into the extension box, last weekend. We are stripping it down, this week.
Definite, lack of drive, here!:hitfan:

The 8-71 will help you make lots of torque when the hull is at it's wettest point. That load is very hard on the drive, wheater it be an XR or Imco Extreme. They use the same gears and other parts internally. That fact has to be kept in mind when operating a boat with a blower.
Anything that puts more torque or load on the drive is potentially a drive killer! Plain and simple!

Like Smitty says, give us more info. You may be able to go to differnt type of drive or modify your driving habits to help the situation. Plain fact is, you have too much torque for the Bravo style of drive, comprimises have be made in order to get any kind of servicable life out of your drive.

Hope this helps.

D*ck

...is there a difference in torque / load on the driveshaft or
vertical shaft between 1.36 and 1.50 ratio?

Bad Influence

I did my share of homework when I purchased my B-Max. If you are under 950 ft lb and hp they will warrat uo to two years. I am almost thru 1 year with no problems. Procharged and modified 280 Velocity.
Bob

I talk to alot of guys on the phone in regards to getting their gears treated,I hear time and time again where someone has a single with fairly big power and drive is semi-reliable (like mine),they bolt on a big azz maximus and next thing you know they are breaking parts they have never had a problem with before. Alot of these single engine boats run anywhere from 15-25% slip,the big 5 blades drop that to below 10%,there isn't really any top end gain,just mid range but the stress on the drive is definately higher. I have talked with alot of guys running cats and twins though with higher x-dimension's that are running labbed 5 blades without major constant problems,I think its the single engine vees that don't like it,and thats only my opinion,i'm no expert by any means,Smitty

Any more info yet?? I'm interested to hear your set-up being I have a very similar boat,Smitty
You can call me at the number on my signature too,I'd love to hear the details on your 272

Not pointing fingers here but that was going to be my question. We didn't get a lot of info on setup and driving habits. You really need to be prudent with the throttle if you want to make a Bravo-style outdrive live with big power, no matter what the brand.

No problem with Maximus
 

Talk to the prop experts ,Julie told me to get rid of them but BBlades I think it was,said they are great .I love the Maximus on my Top Gun,I tried everything else,nothing was even close,including Herrings.But my boat is twins,maybe thats not any help to the guys with big singles,although I have 750lbs torque on each side,no broken parts last year with new set of XRs,none this year with new set of Max Worx Billet,upper and lower.I dont beat on the boat,and no air time,cant afford the down time.Just ease into the throttle boys....................

272 Info
 

My boat puts out 960 hp with 940 lbs of torque, I run a 4 blade 28 and turn it about 5800 rpm max. with the 1.50 set up. With the 1.36 set up I could only turn the boat about 5000 max it wouldnt turn up.

We stripped my XR down today, and it looks pretty grim!
As the drive came off and the driveshaft stayed firmly planted in the gimbal housing, we knew that things looked bad. The nut holding the driveshaft in the upper gearset spline had unthreaded itself. There was metal everywhere. The forward gear has lost a tooth, and there is damage on every piece we took out.
The first sign of a problem was when the oil disappeared into the belows, as the driveshaft slid forwards and didn`t seal up against the oilseal any more.

I didn´t see this coming, but I have to admit that there were so so many high speed runs on nasty water, where i thought to myself, isn´t it amazing what these XR´s can stand........

1 season, four poker runs and 120 hours.

Sure I pull back the throttle when the boat gets airborn, but there are so many short and messy wave combinations where the best technique seems to be staying on the throttle, dropping a tad of tab and a click of the drive and cutting smoothly through at 75 mph.
I shall be at least 5 mph slower in future, slower out of the hole!

So what parts should I use to build an upgraded XR, keeping in mind that I´m ONLY putting 525 hp through it?

Oh, and, as Marcus asked about the Extreme - is there a difference between 1.50 and 1.36 ratio from the point of view of handling torque? Is one or the other better for a high hp (900) motor?

uh, does it get any better with a Bravo? You must be a better throttle man than you admit to:D

If you put a Maximus on and lower your slip to less than 10% it's going to put more strain on the drive. IT'S NOT THE PROPS FAULT, its just a bad setup for bravos. I went to a 2" shorty Bmax with a maximus. The slip is now at 16% and I run well over 100MPH in a single engine Checkmate with a full diameter labbed Maximus 28". Previously I couldn't get past 98mph. Heck, I can break just about any drive with the power I run, but the maximus didn't make the issues any worse and I run several mph faster. Good Luck :drink:

BMAX i tried everyone else don`t waste your money like i did. Single engine cat high X 940hp 5blade max. 6100rpm 114mph no problem:cool-smiley-027:

Oh! Thanks!!!! I guess I missed that paragraph in the my 525/XR package users manual where it says "100 hour/one year service - remove XR and discard, fit new unit" :blaster: :blaster: :blaster: . Can I re-use the propeller, or is it like a sail, that loses its shape after a season?:cool-smiley-011:

I think the procharger & lack of low end torque helps save the outdrive. I can not just pop up on plane, even if I try hard. I have see other cats with roots blower & big props just hit the throttle and are up and gone.

not in the manual but basically the truth, no?

That may be, but I could not get a Bravo to live more than a few hours in glass like conditions and being nice to it. I kept spares. Could swap in less than an hour, I'm sorry to say got good at it.

I still don't think you can go wrong with the B-Max as a direct bolt on.
Bob