Best Performance Mods for Money???

[jesss55]

Hello all. I am a relatively new high performance enthusiast when it comes to watercraft. I recently purchased a 1990 Norris Craft 1900XLV fish and ski. The boat is awesome! It is rigged with a 1984 Mercury 200. The power head and lower unit are recently rebuilt to factory specs. The motor height is sitting at 25 1/4" which according to Mack should be pretty close to optimum. I am currently running a Tempest 25 Plus, and I have a Trophy 23" that I have not yet tried on the water. Current performance with the Tempest is as follows.

Top speed = 68 MPH
Top RPM = 5100

Edited to Add- Set-up includes jack plate with 5" setback. 25 1/4" height is based on recommendation from Norris Craft.

I am looking to increase these numbers, and I would like to make a few modifications over the winter. My questions are as follows.

1. Will I see a bigger performance increase by changing my lower unit or improving the performance of the power head?

2. Should I modify the factory lower unit with a Bob's nose cone kit and low water pick-up or should I switch to a Sportmaster or CLE?

3. How can I build horsepower and throttle response with my factory power head? (Boyeson Reeds, Velocity stacks, exhaust mods, compression increase, etc...)

4. Am I better off to sell this nice stock engine and invest in a high performance engine?

Thanks for all of your help!

Jess Short
[email protected]

[Trikki1010]

I don't have all the answers and don't know the boat well

If your looking for big speed, better off bigger.
If you want to bust into the mid 70's, different issues


Most want to jack the motor so you can surface the prop and minimize drag (Jack Plate), that calls for low water pickups (Nose Cone) and a nose cone is adequate with your gearcase (XR-6??)and speed (bling factor too). This now calls for a different prop cause you'll be spinning more r's (26 Chopper/ET)

Next you can look into the motor.

Many here better at that one than me, but I believe you can relieve the exhaust and cut ur heads and jump it up a notch.

If ur reeds seal, save ur money for better things. That's just like swapping toilet paper, some just feel better but it gets the job done just the same.:eek:

Stacks add bling but not much else, as with tuners and lightweight flywheels;)

Others will follow with better advise:cool:

[largecar91]

You Will See A Lot Of Good Advise Here. I Personally Would Optimize My Set Up Like Trikki Said(prop, Engine Height...). I Think The Biggest Bang For The Buck In Engine Mods Is Cutting The Heads And Raising Compression(if You Have Good Gas).

[jesss55]

Thanks for the advice. What are the advantages of the Sportmaster or CLE lower units compared to my factory lower unit with nose cone installed?

[Trikki1010]

Thanks for the advice. What are the advantages of the Sportmaster or CLE lower units compared to my factory lower unit with nose cone installed?

If you are running under 85 mph, the sportmaster would create more drag and reduce your top end. Since you are 200+/- hp, you would actually benefit from running your XR-6 with a nosecone due to smaller case, skeg and smaller diameter bearings and carriers.

That lower would be the choice for alot of bigger motors if it didn't blow under repeated 280+ hp surfacing loads. That's why the CLE & Sportmaster have the larger bearings and carriers;)

[Fish]

Welcome to scream and fly. Although I am not that familiar with your rig, 5100 seems like you are not getting all the rpms you should get out of factory specs. I think 5800 or 5900 is closer on factory rpms before mods.

I agree with triki about the nose cone and raising the motor. Make sure you get a water pressure gauge before you do this and keep an eye on it as you start raising it.

Best bang for the buck would be to cut the heads to 33-34 cc's. You are looking for 145 compression to still be able to use 93 octane pump gas. you will feel that gain in power and it is relatively cheap to have done or do.

Like triki said, stacks look cool but don't do much else; if you motor was just rebuilt, your reeds are probably fine. Better reeds may help a bit, but in your use you may not feel it at all; exhaust mods is debatable around here. One thing is that you should accelerate a little quicker and it will be a lot louder. Top end is where the debate is. I can't say for sure either way but I know lots of smart folks around here have good arguments for both sides.

Good luck and welcome to S&F,

fish

[pyro]

Dont' do anything until you find out why the RPM's seem so low. Something is off. Maybe the tach, maybe the speedo. 25 pitch turning 5100 would be 60 mph at best. ...and not for long if it's really turning only 5100, the motor will get hot really fast bogging down at WOT so much. Check the tach setting on the back side, and use GPS for speed comparison, the dash speedo is almost always wrong.

5500-5900 is factory recommended range, however the HP peak will be good anywhere from 5800 to 6400 RPM, the higher end of which is ehalthier for the motor than dragging it along too low.

The Tempest has big, cupped blades. that prop won't even let the motor spin up all the way unless it's on the surface where it can do its magic.

Find out where your hieght really is:
1. Level the hull on the trailer by using the nose jack, with a level on the pad.
2. Level the motor by using the trim, with a level on the bare propshaft.
3. Measure distance from pad to garage floor.
4. Measure distance between propshaft CENTERLINE and garage floor.
5. Difference between thse two measurements is your shaft height, in "inches below the pad."

[jesss55]

Thanks again for all of the great advice. I changed from the Tempest 25p to the Trophy 23p this afternoon. I will be taking the boat out this weekend, and I want to see if I can gain some RPM's. I have not yet checked the speed with GPS, and I am not sure how to check actual RPM's behind the tach.

I measured my engine height as instructed, and I am currently 4.5 inches below the pad. Any guide line on where I should be for optimum performance?

Jess
[email protected]

[pyro]

Are you saying that your stock LU DOES or DOESN'T have a low water pickup?
You're WAY too deep for starters, a healthy 200 won't be able to spin a big prop to full RPM's with it completely submerged. Needs to come up at least 2 inches before the prop can really cut loose and run. Low water pickup will allow you to go even higher.

[stealthperf]

I can calibrate your tach for you so it will be 100% accurate at your wide open rpm range if you're interested. If your tach is off you could have a very hard time finding a good set up. Dave.

[The Big Al]

One thing seem to over look and asume.

Do you have a Jackplate?

And if so what size?

If not this could be a very big gain!

[jesss55]

My lower unit does not have low water pick-up. I am looking to send it in to Bob's this winter, however it is currently stock.

I am running a 5" setback jackplate. I may try raising the engine 2" and see if I still have good water pressure.

What is safe pressure at WOT?

Jess

[pyro]

I ask again:

where did this 68 MPH figure come from? A GPS recall or a "fish-story" dash speedo?
You need to figure out which one is wrong first, speed or RPM. You can't possibly begin to optimize performance without knowing where your current setup stands. For example, running a 200 WOT at 5100 RPM is asking for a blown-up motor. OR, it may actually be doing 68 mph, and the tach might be wrong, in which case you may actually be turning 6100-6200 RPM (using 13% slip in the calculation)

This is important, since your 23 pitch might actually be turning close to 7000 RPM while you're out testing this weekend, which would be getting dangerous for an old stock 200. Check the small dial on the back of the tach. Which setting is it on?

you can use a Fluke meter with a frequency counter function to test your tach. Take a long piece of wire and wrap a few turns around one of the spark plug wires without metal contact. It will pick up a weak static signal through the insulation, enough for the meter to pick it up. Ground the other test lead. Run the motor and do the math.

-Chad

[jesss55]

Had the boat on the water over the weekend, and I saw some major improvements. Let me begin by restating that I have not yet checked top end with GPS. The speed I gave above was from an "inaccurate" in-dash speedo. I checked the setting on my factory Merc tach, and it is correct.

The first changes I made were removing the factory airbox and changing props. I changed from the 25P Tempest Plus to the 23P Trophy. This gave made an amazing difference in holeshot. With this change the RPM's still did not increase.

The next thing I changed was engine height. As I stated above, the engine height started out at 4.5" below the pad. I adjusted the engine up to its new setting of 2.5" below the pad. This seemed to really free the engine. The engine is now much more responsive to throttle, and it is now topping out around 6100 RPM's. The lake was rough, and I was not able to get an idea on new top speed, however the boat feels much better.

I would next like to try reinstalling the larger prop at this increased engine height.

Hope to get a GPS speed and some pics posted in the near future.

Thanks again for the great advice.

Jess
[email protected]

[David]

One improvement could be to trade the boat for an Ally XB-2003. You'd pick up 10 mph without engine mods. OK, maybe a nose cone.

You don't need a nose cone unless you are over 80 or don't have >15 psi water pressure. My guess is that your application will not go 80 and will run best with the engine low enough to maintain good pressure.

By the way, you probably have a regular 200 gearcase, not an XR6.

[RLC PE]

I have a 22 foot Sting Ray I/O with a Alpha 1 wich is like a lower unit from a out board. The boat has a conventional 20 dregee V hull. Can anybody tell me a ball park figure for a prop centerline to the bottom of the keel figure.