What's a picture worth?
 

I am continuing to test with the new motor.
The digital GPS on my Garmin Chart Plotter said 100.2 mph.

This was done with a 31 pitch hydromotive Q4x, and a 1 inch spacer. The motor was running a 1/4 inch smaller pulley, on 100 octane unleaded. We were at the Nordic Regatta in Havasu.

The boat was a handful over 93 mph, and was rocking from side to side as the prop torque rolled the boat to the left, and then the hull corrected itself. Definately not for the faint of heart.

Since then, I have decided to concentrate on boat handeling.
To this end, I purchased a new 1" shorter IMCO lower unit with 1.34 gears. The theory was that by using smaller pitched props, the blades would be more verticle to the water, causing less prop torque. Also, by experimenting with shorter outdrive lengths, the prop would have less leverage to roll the boat, and that the shorter lower unit would cause less drag. While working on Jim's 700 Ilmor boat, I discovered that it was the fastest with a 3" propshaft depth, and that at 2.5" , it lost speed, and would not hook up coming on plane even with a P5x. The smaller raked props also have the advantage in that they usually have lower slip numbers than their bigger brothers

I have discovered that over about 93 mph, that the four blades work better on my boat than the P5x does. The four blades have less blade area, lift the rear of the boat less, and don't have as much surface area to prop load the boat.

I removed the 1/4 inch smaller pulley, and filled the boat with 92 octane unleaded pump gas.

My first run was done using a 1/2 inch spacer (3" propshaft depth), and a 27 P5x. The boat still hooks up great on the bottom end, had a 43 mph cruise at 3000 rpm and topped out at 95.2 mph. Over about 91, the boat became a handfull to drive as it started doing the prop torque dance, rocking the boat from side to side at over 90 is no fun.

Next I installed a friends stock 28 merc prop. Cruise speed was down some to 40 mph at 3000 rpm, and I could cavitate the prop coming on plane.... but... top end was 98.8 at 5980 rpm. The boat was so stable, that I was able to look over my shoulder to see how the innercooler water was shooting out of the side of the boat, played with the trim to see what it did to the GPS speed, and gave my son a "high five". We were at over 97.5 mph for over 2 minutes. Wowser! this thing is finally driving like I thought it should... it felt like it was effortless, and on rails!

I am going to try a Merc Lab 28 next to see if I can get some more speed. My peak horsepower is at 6200 rpm. I am looking to break the century mark on pump gas, with an extremely stable boat.

I will still be using a P5x for my daily driver, and when taking the kids out wakeboarding... except for going over 90mph.
I will also be trying the boat with the 1/2 spacer removed to see how it works with both 4 and 5 bladed props on my boat.

Chris

nice #'S:drink:

Did you have anyone ridding in the open? :eek:

Good job Chris

Tim
oregoncustommarine.com

Not! :lolhit:

The boat looses a full 3mph + with the bow cover off.
Robert would probably love a 100mph ride in the bow, with the cover off... doing the Titanic movie thing....but Gina (mom) would kill me!

Chris

Wow!

It sounds like an expensive disease that you have. You should consider therapy. OH wait... This is therapy.

All kidding aside, great numbers and good luck and be careful.
I'm not nearly as fast as that, but I get the same feeling with the P5X as you do. It just makes the boat a little crazy at higher speeds. It feels like the P5X gives the boat stern lift. The 4 blade bravos seem to work best for me.

Sweet.

You made it!

Uncle Dave

I think you just named my boat for me... I ran it by the wife... and she really likes it also.

"Therapy"

defined as the treatment of a physical or mental desease by means other than surgery. .. My wife is a Nurse Practitioner.

Chris

Way to go Chris. I think you are the first and only OB Heat to 100. Not easy to do on any big single engine hull, open or hard deck.
Congratulations,
Steve

Awesome. Just...awesome. Great learning here. Perhaps one day I'll have the ability to replicate this set-up.

Outstanding Chris!!!

Nice family cruiser :evilb:

You are finding exactly what we did with the 5 blades. After 93 they are a complete handful. Although our low elevation testing was limited, we did find that the four blades run like they are on rails above that.
Probably a great move with the gear change. Makes complete sense and my guess is you'll love it. Lower pitch prop should also help keep the boat on plane better for towing the kids around beings the Whipple doesn't mind tugging low rpms :)

Please keep us posted.

Nice work...

Dave

My boat absolutely loves the 1.34 gear... probably because of the very flat torque curve of the Whipple.

You are correct in that it actually planes off quicker using the 28 bravo with the 1.34 gears as opposed to the 32 bravo with a 1.5 gear.

An additional advantage to going to the smaller props, is that my slip numbers went down about 4%.

A P5x is really hard to beat for all around family use... they come out of the hole like they were glued to the water, and midrange cruise is a couple of mph faster than the bravo's. This makes them ideal for pulling water toys or just cruising.

For all out speed and handeling, I like both the bravo's and the Hydromotive Q4X props.. the Q4x's seem to be faster than the Bravo's... but I have not tried a Merc Lab Bravo yet.

Probably because of its 15" diameter, the Q4x slips a little more than a bravo coming out of the hole, but from there on out is 1-2 mph faster per given rpm.

I will be trying a 28 Q4x and a Merc Lab Bravo 28 this next week, and will return and report.

Chris

I think you would shock a bunch of people at the LOTO shootout with the speeds you are reaching! I know you are not close to LOTO but man it would be sweet!

Jt

Nice work Buddy !!!!!!

great numbers chris
 

now you know why i stick with my 32 bravo. above 94 or 95 the five blades are a handfull.

Yup...
but I can also tell you that my boat is faster with 1.34 gears and a 28 bravo than it is with 1.5 gears and a 32 bravo.

Chris

That's because your spinning the prop shaft faster. But you loose a bit of punch. You have enough HP that it is probably not that noticable. It is probably easier on the outdrive also.
Less torque.

1.34 or 1.36 I keep forgetting.
I regeared also.

The upper gear ratio in an SCX is slightly different than in a SC or Bravo upper. Using a SC lower with a Bravo upper nets a 1.36 overall ratio, wherin with my SCX upper, the overall ratio is 1.34 using the same SC lower.

Probably because of the nearly 900 ft/lbs of torque, I did not notice any difference in acceleration.

Chris

It seems, for me at least, that the lower pitch props also lower slip. I tried the 28 lab @ 5750 ft. elevation hit 81 @ 5700 rpm. These are about -2 speeds my 32 lab gets @ 5100 rpm at 4400 ft. elevation. Of course the 28 bounces on the rev limiter @ lower elevation & gains me no speed (in fact I loose 1-2). 15-16 slip for the 28, 17 for the 32. The 28 was stable as could be, could take wide turns @ WOT in 1-2' chop, something that the 32 makes a handful driving straight. It's all about trades, hole shots, cruising & handling.
I wish I could afford what Chris is doing with drives & things, seems you figured this all out.

What kind of HP do you have in your heat.
 

Hey Chris,

First, is your avitar picture taken at Lake Billy Chinook in Central Oregon? We go there all of the time.

I am pretty sure that I had the first Heat in Portland.

Our stock 502 is at almost 500 hours and I am thinking of working on the engine this winter.

I don't want to go 100 but I would sure like my Heat to be an 80 MPH reliable boat. I have watched your posts for a couple of years and you seem to have tested - just about everything available for purchase in the marine market.

So if you have a minute. Horsepower range and drive etc. for the 80 MPH mark would be awesome.

Thanks,

stock stoutman in Portland!

Stoutman,

The picture was taken at the sand bar, on the Columbia river.

As to the second question...
600 horsepower is what you need to get going 80 mph in a Heat.
I don't know what year 502 you have... but the easiest route there is probably by installing a 4.25 stroker crank into your motor when you re-build it. This will make it into a 540.

You will need to set your outdrive depth at aproximately 4.5 inches. This measurement is taken from the lowest point on the keel...to the center of the propshaft.

For props... I would recommend either a stock 28 Bravo spun at 5400... or a Merc Lab 30 spun to the same rpm. The 30 will be faster...but is a more expensive prop.

Hope this helps.
If you have any more questions... feel free to give me a call or ask here.

Chris
206-235-4545

I had the same dilemma last winter. I had a 415 hp 502 in my 2000 heat with 400 hours that was making some valve train noise. I had the motor completely rebuilt using 8.75:1 blower pistons, a 525 cam, Dana marine exhaust, and a top mount 2.3L whipple. I'm around 650 hp and am very close to 80 with a 28p bravo running 5100 rpm. A labbed 30 should put me 81-82. Like Chris said, pay attention to your drive height. Most heats running up till 80 need a 1" spacer. Mine was a handful after the hp upgrades till I added the spacer.

Hey Chris,

I'm Brad and I am thinking the following on the rebuild. Give me your thoughts.

Fresh the motor.
Dart heads.
Pro-charger with intercooler.

Here is the issue. Different intake as the one on the 502 chokes the engine. Thoughts and suggestions here are what I need. AND completely unsure of which direction to go with this.... Holly... ?? I know I am showing igorance here... Buy Mercury Racing someting?? Help.

R and R the exhaust (keep in mind we still want to tow the girls and their friends on the tube (below 50))

I would really appreciate everyone's feedback on this task. I don't want to build a machine that is fast and not useable for family life and I love turnkey. I've built a few Camaros that always needed attention. You know - when they need to start!!

Input is appreciated and respected!!

I hope everyone has a great Labor Day while it is 62 in Portland tomorrow.... feeling like pulling the engine and putting the boat back in storage...?

Brad

The easiest way to get horsepower is to bolt the Whipple kit on your motor. It will get rid of the lousy intake, is a complete kit, and you will have a 82+ mph boat with turn key reliability. 05R1 aka Ned, put a 2.3 whipple on his 502, and we got the boat going 82mph on friday. He scabbed this kit together off of buddies and craigslist... and the boat ROCKS!

Here is the formula for a sure fire...reliable setup... You should easily get another 500 hours out of this setup.

Rebuild bottom end with blower pistons
Set compression about 8.5 to one
Keep stock heads
Install 525 cam (RMBuilder aka Bob Maderia, can get you an exact copy 585-654-8583)
Install Dana exhaust (best bang for the buck!)
Install this kit: http://www.whipplesuperchargers.com/...sp?ProdID=1150
Talk to Dustin Whipple at: 559-442-1261 for any technical questions about your setup
Put a 1" spacer on your drive (you can find them used for about $100)
Run a Merc Lab 30 pitch prop (a stock 28 Bravo will work also...but will cost you about 2mph)
Drive boat for 400-500 hours (top speed will be between 81 and 84 mph)
Smile alot!


I agree with you on the Heat. My boat does consistantly over 100mph, and I can still pull my kids easily on an innertube or take the whole family (and kids friends) out for the day and have fun. A cat can't touch this thing for versatility!

Chris

P.S. If you need someone to do the motor for you...or recommendations...give me a call 206-235-4545

Hi Brad,
If you want to stay naturally aspirated, I think your 502Mag rebuilt to a 540" (4.25" crankshaft and .030 overbore to 4.5") will get you pretty close. You'll need new forged pistons (8.75 CR) and rods. You are correct about the restrictive intake and small CFM throttle body on the stock motor. There are several nice EFI intakes with large bore throttle bodies that would be a big improvement there. I think your heads are rectangular port GMs, which aren't bad, and could be upgraded. No doubt Dart Pro 1s or Iron Eagles would be better.
The 525 cam or a clone would work great. And of course you'll need to upgrade your exhaust. I think you would easily get around 600 (stock heads) to 650 (Darts) HP out of this combination.
Then if you wanted to supercharge (now or later), you would have a good strong bottom end already built. Personally, I like supercharged motors. As Chris says they can make very nice horsepower with good reliability. The Whipple 3.3 or 4.0
would top this motor off nicely.
You will probably need some rigging upgrades (hydraulic steering/spacer/beefed up drive/propeller) to go along with the additional horsepower and speed.
The good thing is you have great hull to work with. They handle very well with additional power.
Regards,
Steve

Chris and Steve,

Thanks for the input. Which drive do you think would be adaquate for that installation. XR? I just have a standard bravo now.

Thanks again.

Brad

A well built XR will handle 600/650 HP no problem.
Actually they will handle a lot more if you service them regularly. Oil change/magnet inspection every 20 hours, or after every poker run, and partial teardown/inspection (gears/bearings) every off season.