Merc 225 ProMax Question .... 26 cc heads

[JohnR225]

I am running a 1996 225 ProMax with the following:
Oil injection removed
260 stator and lightened 260 flywheel
ECU adjusted by Rapair ... midrange/ 7500 Rpm's
screens pulled from the injectors
Brucato SVS
35 cc heads on premium pump gas

My question is have any of you guys experimented with 26 cc heads on a 225 ProMax?

I was looking to run the 26 cc heads for a day of drag racin fun ... just with friends.

Will this destroy my 225 ProMax with the two bolt mains?

What octane would I need to run?

I'm looking for low-end PUNCH to leave out of the hole faster on an Allison XB-2002

Thanks for your experience and ideas.

[O/B Dude]

As long as you have adequate fuel quality and delivery, it won't hurt it for weekend race duty. I have heard people talk about spinning Pro Maxes too high or running too much compression, and grenading the motor. Before the rebuild, my motor was a stock 225 PM with carbs, 245 stator and flywheel, and land and sea exhaust adaptor/tuner. My heads are cut for 150 psi with the thin gaskets. I regularly ran the motor to 8000+ rpm with cast pistons, and hit the low 100's. No problemo. I took the motor apart for porting and rebuild and there was virtually no wear. Everything looked great. 26 cc's is pretty tight on a 2.5L. You'll need to run race gas. My 2 cents.

[JohnR225]

If I decide to run 26 cc heads what octane and is my stock timing okay?

[steve]

Stock initial and 24-26 on the top. 100 octane . You should add 92 pump gas to the race fuel to achieve close to 100 if you have higher octane race fuel. If you have cast pistons then 8,000 is really about it or they like to fold the skirts over. Also the newer 1999 and 2000 models seemed to lose the locator pins more easily then the older pistons. At least thats been my experience.
You WILL need to richen the ECU a bit over stock or 34cc heads. Easiest way to do that is an adjustable fuel pressure regulator like a Mallory or Bosch. Get a guage and see what you have with the stocker and then add a few pounds. Check your piston color and plug color. Also you might want to try a set of Platinum or Iridium plugs. I believe the NGK is a BP8HVX or a colder one is the BP9HVX. Here's a link.

http://www.clubplug.net/retail_vx_ngk.html

They do help keep your little 2 stroke from fouling. What props do you plan on running? How do you have the bleeder hoses that come off your intake just below each reed cage hooked up? More info on your boat setup would help as well. Do you have a launch plate on the gearcase? That hull likes a some plates on both the boat and the gearcase to launch straight and quick. You will die at the line without them. There are other things you can do I'm sure.

[pirogue]

i've seen Jay Smith post octane level of 4gal race(110) and 1 gal (93) for 180#'s of compr. and that's probably what you'll have.

your stock timming should be 25* if so yes you will be fine.

the motor should have no problems with those heads and fuel, a friend of mines ran dsra with stock 225 and 26cc heads, had the rev limiter removed.

if your running a small wheel, just keep it at a 1/4 mile and you should be ok.

post back here and let us know how you make out.

steve said exactly what you need.

[steve]

to achieve 100 octane with 110 race fuel, you would mix approx 1/2 and 1/2. Here is the formula----110+110+93+93=406 . Then 406 divided by 4 =101.5 octane. If you run 91 octane pump gas then its right at 100.5. Also you will probably want to at least try a 26 Yamaha. It may hit the limiter at 3/4 track but it will be the fastest prop. A 27 SRX will be good as will a 26 small ear chopper.
Tell us more about the boat setup. Thats where its really at. :cool:

[JohnR225]

As for the XB-2002 (center steer) I am set up pretty light. I have the foil and a homemade skid/drag plate bolted 3" below the jackplate.

I have an arsenal of props from Yamaha drags to Lightning ET's.

Every year in May we have an Allison Owners get-together in California, we call it W. A. R. (Western Allison Rally) this May will be our third WAR. There will be more 280s on XB-2003's and a lighter comp Super Sport. We also have a 300 Bullet and 300 Stroker. We're a small group of friends that are competitive on the water and enjoy steak and beers together in the evening. Every year we all get a little faster ~( :

One of these years there maybe a JSRE 260 under the 225 cowling, but until then don't count me out...

Lets Drag baby!

[RB in NM]

You jus' need a lil' bottle to feed that pup ! LOL !

See ya at the Rally !


RB

[steve]

Get an Aerostar Switchblade prop, 20 / 26 or 21/27 and you will really be smiling! The Aerostar would be perfect for your setup. It will net the big end and and be at least 3 boats faster then your best Yamaha in the 1/4 . Plus you won't need to be spinning the rpm to get the ET. Since you aren't running a santioned event and can run whatever you have, this is by far the best prop to run. We have run them up to 9000rpm and over 100 easily on our 2002. You can surface them and you want to run about even with the pad ( a little higher then you'd run a Yamaha) . That prop will need a hi rpm kit if you spin it past 8000. Call Aerostar and see what you need. I'd consider renting you one of ours if you are interested. The photo in our avitar is with an 18 / 24 Aerostar on. :cool:

[JohnR225]

Russ it is going to be a lot of fun... I know those guys think I have NOS but they cruise this Scream and Fly too and now they will be rest assured I don't have the bottle.

Aerostar Switchblade prop... I don't mean to be rude (but I am) are you ****tin me? Better than a Yamaha drag? I have not ran anything better then a Yamaha Drag or ET but his prop would be three boat lengths better and you would rent one out huh? this sounds like a too good to be true thing... If its for real I would have to see it to believe it. Like they say you can never try too many props.

[RB in NM]

I've heard of some guys running those Areostars on HP rigs with good results. I have not tried it, yet... I have seen one of them blade slingin',spring loaded, don't-run-it-by-me land and sea auto swicthing props in action. I waz impressed, actually a lot !
But it waz on a crusier rig that was limited on the prop height, so it was buried. The durability of those L&S things just ain't there.I have heard this other one is purdy sturdy.


I can see it now John,,,,you'll have one of them prop covers over that Areostar soon.....the sleeper prop !

Russ

[TB21]

Steve where do you buy one of these props at? TB

[O/B Dude]

Steve, I have never run a switchblade or L&S prop. I know people who have run the L&S and said that surfacing WILL grenade the prop. I assumed the Areostar would have similar issues but also heard the Aerostar was much stronger and better made. My question is, how tough are these props? Can the Aerostar be run surfacing, on a hot lake boat, say an STV with a 280, and not grenade? I always wanted to try one but figured it would come apart if I surfaced it. How long will they last? Whats the real deal? Thanks!

[O/B Dude]

I got this from a brochure mailed to me a few years back:

Aerostar Marine
3608 S Davison Blvd
Spokane WA 99224

509-455-6577
1-800-442-4245
www.soar.com

I havent called Aerostar, but I did try the web address in the brochure and it says page can not be found.

[steve]

The L&S is junk. Needs a lot of tweaking and will throw blades.

Again, my avitar is a photo of the Aerostar run surfacing on a stock 260 / XB2002 combo at about 100.
The Aerostar is a solid pc. They DO have a website and they also make airplane props.
The blades will be within 1/4 P of dead on . They don't slip much either. They have excellent top end and of course bottom end. On a 2002XB you will need some practice driving. It will come off the line like you have 500hp and will shift about 100ft out. Feels like a powerglide with a shift kit. The boat will want to twist a bit when it shifts. Now this is with a 260 and a 24 so figure on a little less spectacular but strong performance. Marv J. at Chopper City and I both did a lot of R&D on this prop for Frank at Aerostar when he was working with them.
If you spin the higher rpm then you will need them to install the hi rpm kit that has the lighter weights and a few other things or it will lock in high pitch after a few strong runs. It will without a doubt beat a Yamaha , especially short track. The yamaha will run a few more mph, but the Aerostar will air the boat out better all the way down the track. You'll like it with a load as well. They run about $1000 plus the kit so they are not cheap. I have 3 of them. You can still buy them as they started making them again. I am in the process of getting a titanium hub made. Blade sets are $150 if I recall correctly and there are 2 styles . I think we ran the SRX style blades on the 225 on Lees boat. It ran 98mph with that prop and a stock 1995 225 ProMax.
If you can find one, buy it. And yes I will rent one. Full purchase price up front and returned minus the rental fee. That way if you go stump jumpin we don't get screwed. I believe the 25 is my largest right now. That would put you around 94-95 mph at 8,000. Call me and I will tell you a few more tweaks for your boat.

[O/B Dude]

Steve, thanks for some really great info. I had no idea the Aerostar was so strong, or that the blade design was sufficient for high speed. I'd really like to try one out. If I rent one from you for a weekend, how much is the fee, and I don't suppose you take a credit card for the fee and deposit? I wold love to have one set at 20/28 or 18/26. I don't know if they are available in those combo's. Anyway, very informitive reading. Thanks again!

[JohnR225]

It looks like these props go up (shift) six pitches...20-26, 22-28 etc. I am just a few hours from Spokane, WA. If they came with a year or better warranty I may be interested.

[steve]

815-626-6738

[O/B Dude]

Steve, I'll call you after I get my motor broken in. I would seriously like to try one of these props. Thanks!

JohnR225, according to the Brochure I have (Its a few years old) they offer a warrantee for 2 years on motors up to 420 hp! AND have a 30 day, no questions asked moneyback if not satisfied guarrantee. My brochure is from '97, so I don't know if they still offer that or not. Sounds too good to be true, (Like the L&S prop was) but Steve has a lot of credibility in my book. If he says they work, I'm interested.