Heat X
 

Anyone know (having set-up and run personally) the right X dimension on the Heat?

Yes,
What are you running into? If it's excess slippage (high teens to 20%), and/or lack of bow lift, you are probably too high.
For years, the step hull boats went out at 19.25"s, which is just too high for most Heats.
I have a 1" spacer in mine, making it an effective 18.25"s. Props also have similar effect. 5 blades will perform better than 4 blades at 19.25"s because of their additional blade area. I never had much luck with Bravo 1 4 blades at the stock XD. They will work at 18.25"s. The 5 blades don't seem to mind the extra 1" of depth either.
I am also running an Imco case which seems to help by loading the prop better at speeds above 85. And it handles very well at speed. Keep an eye on your water pressure if you add the Imco. They ram a lot of water at higher speeds with their LWP, and it will send your water pressure through the roof.
Regards,
Steve

My problem has been RPM's. I need to spin above 6 and for the life of me I can't seem to get there. Slip always around 9ish. Bow lift not a problem. Getting on plane, no worries what-so-ever. Every prop I run whether it's a 4 or 5 blade I always top out around 5800. I've run stock 26 and 24 B1's as well as labbed 26 and 24's with very little in the way of movement on my tach with almost identical results. My thought was that I may have to much drive in the water and might need to shorten the lower (Imco standard height with lwp) but I'm not sure what it's currently set in terms of XD.

Don't get me wrong... the but runs great but I know theres a little left and it bothers the $$$hit out of me. In havasu last week at 113 with 15 gallons and 2 people (25 PX5) I ran 88 at 5800. Put on a labbed 26 B1, little more fuel but just under a 100 when I ran, 87 at 5750........

You may be running out of torque. Most engines make peak torque at 4200-4400 and about a 1000 rpm after that the curve drops fast. A super charger flatens the curve but it still falls off in that range due to the cam size. Boats respond to torque more than HP. The faster you go, the more drag, the more torque is needed. AT those speeds in a heat. the hull vs HP could be at the max. Just a thought. Steve & Dave have the most experience with these boats
Good Luck

I also remember some conversation from someone regarding your boat. That conversation was concerrning correcting the drive height. They told me that yours had been lowered to 18.25"s. Measure from the bottom of the gimble to the top of the notch (not the XD, which is a little more complex) along the transom. I'll measure mine and we can compare.
Linster's comments regarding HP and torque are valid too. I have never run an Ilmore/Viper, and don't know much about the 700. A friend in Knoxville, TN has one in a 26' Lavey Craft and it runs really well....low 90s/high 80s. Sounds a lot stronger than the other 2 versions.
With those small props turning the same RPM, your rev limiter may be set lower than than you think. I would get a knowledgeable tech/rep to run a scan and check the limiter.
What is it supposed to be set at?
It may just be the heat. With the exception of the new Merc 600/700/850/1075 with variable boost, all of our motors are going to fall off in high heat and humid conditions.
Regards,
Steve

As far as the rev limiter goes, I have spun one prop at 62. I dropped to a labbed 24 B1 (done by a certain havasu shop). My slip went through the roof and my speed fell way off (7-8 mph).

I'll play with it a little more this week and see what I come up with. The latest props, a stock 25 PX5 and a Bronson 26 B1, both ran well in the heat last week so we'll see what they do at altitude. The only problem, we're supposed to be in the mid to uppper 90's here all week too.

just measured
 

From the top of the transom notch, to the bottom of my transom bracket (not the trim line housing), measured along the transom, is 6 3/4"s.
That equals 19.25"s XD on my boat.
You might want to measure yours.
Regards,
Steve

I talked to IMCO and they had me measure in a different direction.

From the bottom of the keel to the center line on the prop shaft = 4 1/2". The drive needs to be level with the keel of the boat.

The "X dimension" is the vertical (not measured along the transom angle) distance between the driveshaft, and the bottom of the boat.
I use a flat or square yardstick taped to or held against the pad. Then, you can measure off the top of the yardstick with a framing square, to the tilt pins on the side of the gimble bracket. The tilt pins are located at the same height as the drive shaft.
It does help to level the yardstick, and check the framing square for vertical alignment.
Since I know mine is 19.25" measured this way, I thought you might want to measure yours "the easy way" along the transom from the bracket to the top of the notch. If your's measures 6 3/4"s, you're at the same height. Above (unlikely)or below that, would give you something else. Either way, you would have a known height to work from.
For instance, 19.25" is generally too high, and a 1" spacer usually results in much better slip %s with a 4 blade. If your "bracket to notch" measurement is more like 6"s to 5 3/4"s, you are lower by 3/4" to 1" and closer to what we have generally found to be a better performing XD on a Heat.
What Imco is asking you for is propshaft depth. Another practical way to determine gearcase and propeller depth. That is partly how they determine whether or not a nosecone, standard length Imco case, shorty, or spacer would help a specific boat.
What did they say?
Good luck and keep us posted with your progress.
Steve

What was the slip with the "labbed 24 B1 (done by a certain havasu shop)." at what speed/rpm?

RPM's ran up to around 61, slip around 20 speed at 80.

Steve,

Do you have the dimension from the bottom of your keel to the center of your prop shaft?

Thanx,

19.25"s, measured vertcally.
Steve

What slip are you getting with the other props that you have tried?

9 and 10's

I was talking prop shaft. Should be in the 4-5" range.
From the bottom of the keel measuring down.

I'm out of town right now, when I get home late friday, i'll measure mine the other way.

Sorry,
I see you said prop shaft, not driveshaft. I am out of town too.
Will measure that when I get back.
Steve

Good deal...

Thanx

Does this particular Havasu Prop Shop happen to be located next door to the Nordic factory?

This particular shop is on Acoma (as are a few others).

Sorry, I made it sound like I am familiar with the Havasu area but I am not. Is Acoma located by the Nordic factory?

My interest is in that I am running a Bravo 28P that was labbed by the prop shop that is next door to Nordic.

Is it not doing what you want?

What's your slip like right now?

On a 3700 pound dry weight Nordic Rage assuming the 28P labbed Bravo 1 is actually a 27P (per Throttle Up) I was getting13% - 15% slip at WOT at 5350 RPM. I am just trying to deternmine if the prop is working properly. If it is so be it. If it is not I want to know that and get it working properly. I added a lot more HP/Torque over the winter and now when I mash the throttle at about 3000 rpm it is almost like borderline cavitation. It is like the additional torque is over powering the prop at that point. The engine revs up more than the boat speeds up though the boat is significantly accelerating. With the additional HP I am now up against the rev limit. I am increasing the rev limit to 6000 rpm to let the engine find its new WOT speed/rpm (the new internals will accomodate this).

What kinda of power are you running?
Tim
oregoncustommarine.com

Around 600 plus or minus. Will not know for sure until ECU recal complete and run dyno test.

Steve,

From the bottom of the keel, measured vertically from a level, I measure 18.25" to the pivot point/drive shaft.

Your thoughts?

Interesting,
I heard through the grapevine that the factory had come to their senses, and dropped their X dimension 1". Probably from the suggestions of their dealers, and what they have read here.
I can tell you from my boat and several others of the earlier ('01 to '06) models that all of us (here), have lowered our drives. It seems like 1" has been perfect on 90% of our Heats, which is exactly the same as your 18.25"s.
I think you are right where you need to be.
I would play with props. Have you tried a P5-X?
Best Regards,
Steve

Tried a worked 25 PX5 and didn't really like it. Felt like to much stern lift for my boat. In terms of performance, it ran about 2mph slower compared to the B1 and the R's were about the same.

I've been towing with the idea of a labbed mirage (3 blade).
I have no hook-up issues what-so-ever coming out of the hole so I figured what the hell, see what it does.

FYI,
The P5Xs, properly labbed, are as fast or faster on my boat, and much more efficient in midrange, and much quicker under hard acelleration than B1 4 blades.
I haven't run a Mirage on a Heat, but on my last boat (24' Baja H2X with 600HP), it broke loose under hard accelleration and cornering. Slightly faster (maybe 1 MPH) with a light load on a long stretched run. Still very weight sensitive.
Steve

We have one Heat that did not like the spacer however two that loved it.
The one that did not like it was the fastest of the three if that matters. Tended to walk a bit with the spacer and Bravo.
A 30 P5-X tuned by TU ran 94.3 GPS at Lake Powell (3600 feet elevation) last year in 105* degrees, 5 people and over half tanks.
This year with a stock 32 Bravo it banged the rev limiter at 5950 and ran 98 and some change in Havasu in 90* temps. It was not done pulling but a gear change here would be the only reasonable switch but then he would lose his high altitude benefits which is where it spent most of it's time.

So the P5-X can be worked to run very well. He actually used it most for long cruising at Powell because of the overall better efficiency, handling through the canyons, etc... but it is no slouch by any means.

Hope that helps some,
Dave

What kind of power and gear ratrios are these boats running?

It's actually one boat running those speeds and it has a 548ci R-Tech Supercooled M3 Procharged EFI setup running 1.5:1 Max Machine Worx drive.

The two that liked the spacer were an HP500EFI and a Whippled 496HO set up (full build) with ~700hp. These both benefitted very well from the spacer. Much better cruise and a 1-3 mph gain on top.

Dave

X-dimension update: 09 Heat

The distance between the notch and the bottom of my transom assembly is set at 6 3/4 inches. This gives a propshaft depth 0f 3.5 inches below the keel when the outdrive is set parralel to the keel angle. I could not get the boat to hook up very well in this configuration, and it shot a rooster tail that looked like a jet boat. I installed a one inch spacer (which brought the propshaft depth to 4.5 inches) and the boat feels much better. I am continuing testing,

Chris

Chris,
Interesting. That's exactly the same XD as mine. It looks like the factory sets the XD according to moon phase :rolleyes:.
I thought they got the memo from us, if not the dealers, that 19.25"s was too high. I guess they didn't..............
You're on the right track.
Keep us posted with your progress.
Steve

That's right where I'm at, but I think I'm a 1/2" too low.

What kind of numbers are you running now compared to before?

Southocg,

I agree that because of your extremely low slip numbers, your prop is probably 1/2 inch too low for optimum speed on your boat. I think that each boat probably needs a little different x-dimension based on weight, horsepower, balance, open-bow vs closed bow etc. I don't understand why Nordic is continuing to put the x-dimension so high. I am even considering going 1/2 inch lower to see what it does with my boat.

I was having problems with the Smart-Craft shutting down the motor when the trim was anything above neutral trim. The trim sensor was incorectly adjusted from the factory, and the Smart-Craft throttles down the motor when it thinks the boat is over trimmed. Tim from OCM finally figured this out, and he and I fixed the problem on Saturday. We have not had a chance to truely test the boat since then, but I will be out on the lake on Thursday doing testing.

Best speed to date is 80.1 mph spinning a stock 30 Bravo at 5100 rpm. This is with the nose of the boat burried because we could not trim it up without the motor shutting down. We thought it was hitting the rev limiter, and could not figure it out at the time. I took the boat out on Sunday with my family, and was able to trim it out, but was not going to open it up with 4 kids on board.

I will let you know how things go on Thursday.

Chris

P.S. Even though we have been running negative trim with our testing, the spacer was worth 2 mph

Chris,

Keep me posted with your numbers.... I'm curious to see what changes.

I more then likely will be swapping to a 1" shorty and then space from there. Like I said, I think I'm about a 1/2" too low.

If I picked up a couple MPH, I would run a legit 90+ at sea level maybe a hair over, 91 or 92, which would be pretty respectable for that boat with that power.

thanx,

Jim