Is 100MPH within reach

[Dave's ZT260]

I ordered a blank 2003 ZT 260 last year and started to build it for triple digits. I seemed to be in uncharted water so I powered it with the best I could afford. Mercury 502ci with AL heads, solid lifters, Whipple 3.3L super charger, and a Sportmaster XR outdrive 1.35 ratio. The dyno says 850+HP 6100rpm. GPS is at 92MPH but 100 seems a ways off. So I am trying to see if anyone has suggestions. I plan to swap blocks to a 558ci and change cams.

 

[SCT]

ZT260,

Call Harold or Jason Kunkel at Kunkel's Marine in Mansfield, OH. They are a long time Checkmate dealer and have set up several 100+ mph Checkmates. They just had a 270 running in the 108 mph (gps) range. Plus they have lots of Prochargher experience and they are great people.
Good Luck.

 

[JW]

Just curious, did you have the factory blueprint your bottom? If not, that's good for a couple mph..............

Checkmates owned: 1995 Pulsare 2100BR/1995 Mercury Promax 225 2.5 EFI. 1995 Persuader 183/4.3 LX V6. 1992 Pulse 171/1992 Mercury XR6 150 hp 2.5 liter.

 

[Dave's ZT260]

No I didn't have them blueprint it. I was not as determined at the time. Can it be done now? Seems like alot of work.

 

[Chris]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by SCT:
ZT260,

Call Harold or Jason Kunkel at Kunkel's Marine in Mansfield, OH. They are a long time Checkmate dealer and have set up several 100+ mph Checkmates. They just had a 270 running in the 108 mph (gps) range. Plus they have lots of Prochargher experience and they are great people.
Good Luck.<HR></BLOCKQUOTE>There is also a link Kip put up to the site where that fellow posts. It's a thread that says "Shoot Out".

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Webmaster
Checkmate-Boats.com-The Fanatics Home!

 

[Chris]

Here ya go...try the links in this thread.

Shoot Out! thread

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Webmaster
Checkmate-Boats.com-The Fanatics Home!

 

[vinny p.]

Welcome to the board !! That is one serious boat. I should have done like you did and order a blank boat. I ended up changing over so many things and waisting money, you have the right idea.. I do not have much knowledge with superchargers, but if you were to up the cubic inch by 56, would that charger you have be able to pump enough air? Maybe just a pulley change would be required? What r.p.m and prop are you running? My next years project will be to add power. I am looking to add a Whipple to my exixting 454 magnum. But, then I think about how much more complicated that makes things. Sometimes I feel the smarter choice is to keep my existing motor, and just build a big inch N.A. mill. That will keep it nice and simple. I just hate to go back in time to carbs. again.

 

[Eriktheviking]

Now Thats the way to build a boat!!! Nice Work

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87 ENFORCER CUSTOM EDITION,454 MAGNUM SS ALPHA W/CUPPED 22 PROTESTOR PROP

 

[175checkmate]

Great looking boat. Seems to be a killer set-up. Well thought out. Good luck in your quest for 100+. Keep us posted.

1975 Checkmate Tri-mate 2, 2.4 200+ / Sky jacker 6" plate / 25p Laser 2 prop, Currently the boat is undergoing overhaul.

 

[Eriktheviking]

How much difference was there with prop changes?What do you run for fuel? I'm not an expert but here are my thoughts.If money is no object I'd go with more carburation, Larger blower or overdrive the one you have more.I know Merc. ran twin 700 carbs on their SC engines in the early ninties.Is that a Dominator on there now? Are the heads ported and polished? CMI exhaust might flow more than the gils that are on there now. Most offshore guys run them.Obviously,a large diameter custom prop.Now that you've done that,can I please your have your old engine.That is one BAD looking piece!! Great Boat!I'll see ya on the Hudson!

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87 ENFORCER CUSTOM EDITION,454 MAGNUM SS ALPHA W/CUPPED 22 PROTESTOR PROP

 

[Dave's ZT260]

To run over 80MPH I switch tanks to 110 octane race fuel and pump 12Ibs of boost in. The only Prop I've seen to work well on big block checkmates over 80MPH is a mirage plus (I've tried almost everthing else). I'm running a lab finished Mirage Plus 24 at 6000rpm. When I did the math, the dominator I have should supply more than enough CFM. The heads are full race setup. I'd love to put a bigger blower, block, exhaust and cam in, but I not sure I want to put 20K in it right now. Speaking of which I should have a complete motor leftover when I'm done. If so I'll post it sometime over the winter.

 

[jrumon]

Nice rig!!! Wondering what your "X" dimension is like...If factory cut the hole, it may be too deep for big numbers...Since raising a hole is a major B*tch, I would seek an Imco shorter lower to try...It might free you up that extra 5 or so MPH...

Also, You need more pitch on your prop...you have the right ratio if your motor is making that much "dyno" power (was that HP with your marine manifolds, and silent choice set up on it). Keep in mind the rake on the bigger pitch props work much more efficiently at higher speeds. (bigger pitch at lower RPM is less percentage of slip) than a lower pitch prop spinning faster...

I just sold my 23' Warlock offshore (V-bottom)with a 532HP (dyno) motor...and saw 85MPH on GPS with a 1.5 ratio, 3" raised X, and a labbed Mirage prop.

Also, those maniflds your running are less than ideal if you plan on more cubes or boost...way too restrictive!!! Look into a set of big tube Lightnings or CMI's...They flow like monsters compared to performance "manifold style" set-ups. I also noticed you have the silent choice still on it which is also a restriction compaired to a clean un-interupted 4" stainless pipe. I think your choking the motor's potential...

Good luck, Jim.

 

[Dave's ZT260]

X dimension is 17 1/2. I wanted it high. I spaced the drive down at one point and didn't lose any speed but gained alot of handling. Going up on the X really hasn't helped me.

I have thought about going to 1.5 gears but mercury racing said it wouldn't help. I need help from someone who has done this already, and the list is very short.

I plan to change exhaust this winter. But the Silent choice has to stay or I'll be divorced.

 

[jrumon]

You are the ONLY one with that set-up as far as I know. The X seams right...and I would run that gear ratio with your motor combo, but you should be able to swing more prop than a just a 24... What RPM are you getting with that prop??? How much trim is needed to get the hull light??? Maybe the drive needs an extension box or just a lot of better prop testing??? I have NEVER heard of any bravo driven 100+ boats swinging less than a 28p (bravo 4 blade) with your ratio???

P.S. Keep the silent choice

... or your wife (or x-wife) would own the boat! It's too nice to loose (the boat anyway)...

Jim.

 

[Dave's ZT260]

Wiht the 1.35 gears and Lab finished Mirage 24 pitch I see 5900RPM. It takes quite a bit of trim to lighten the bow (too much). But the mirage is the only prop that gives me the lift I need and it only slips about 9-10%. The 4 blade Bravo is slow on my boat. It seems I need more HP and more pitch. Just wish I could find a prop with more lift.

 

[vinny p.]

How long have you been runing that drive? Pushing 6000 rpm with a Bravo is reaching the oiling limitations. It will aerate causing a failure. You need a much bigger prop to kill some rpm.
Here are the #'s as I see them from your previous posts.

Using this formula pitch X rpm / ratio / 1056

24 x 6000 / 1.35 / 1056 = 101 mph subtract about 9% slip= 92 mph

Looks like the numbers are exact correlation with your previously posted GPS speeds.

If you are looking for lift from a prop, I believe a Hydromotive may be your answer.

 

[Dave's ZT260]

Which hydromotive prop did you have in mind? Hydromotive told me none of their props have more lift than the mirage.

I have run this drive about 50hrs so far. I really can't do much about the rpm since on sportmaster drives the gears are changed in the bottom unit. No one has ever said anything about oiling problems.

 

[vinny p.]

Last winter, I was in the market for a new prop. I contacted Hydromotive, they recommended their Q-4. They told me that it would have more lift than a Bravo 1. However, I didn't go with their prop, I ended up with a labbed Bravo 1 from Throttle-Up in Florida. I couldn't be happier with the results.
As far as oiling problems, I have been told that stock Bravos' aerate the oil at about 6000 rpm, that's why Mercs # 6 drives are dry sumps.
Why would you want to spin the motor that high anyway? Is that where your peak power is? If not, why not prop up to kill some rpm's?

 

[Dave's ZT260]

As with most supercharged engines, mine makes more HP the higher the rpm(about 30Hp per 100rpm over 5500. I plan to turn 6500 next year with some valve train mods. Unfortunately #6 drives require a transmission, and I don't have room for it.

I can see a hydromotive prop having more lift than a brave, but not a mirage. I'm all ears if someone thinks otherwise.

 

[vinny p.]

I am sorry, I was comparing the Hydromotive to a Bravo. I forgot you are running a Mirage... My mistake...