SuperChiller for 29 Fountain w/575sc

[VP]

Originally Posted by tnothin

What was your stock X Dim. and now what is it, how much speed did you pick up.

1 -- I went from doing 80 to 82 mph on GPS on a "good day" with the stock 30" Bravo1 prop when i first bought the boat used -- it had 140 hours on it, but the tug would not get on plane with 6 adults in it - that pi$$ed me off.

2. so i called Joey Griffin and he sent me a blower pulley off an old 525 SC motor (that is the pulley that is about 3/8" dia smaller) my boost went from 4-1/4 to 6-3/4. Boat got on plane and ran 82 - 84 mph any day (as Need-for-Speed said ..... the test report for my boat was 84 mph with Reggie at the wheel)

3. Then i freshened the motor - took .010 off deck and heads, plus did a valve job - woke the tug right up but banging the rev limiter at 85 mph

4. So i bought a new 32" labbed B1 prop - 86 mph in 50 degree air

5. then i added water injection - boost dropped to 6-1/4 - no more top speed but cooler oil temps and it maintains timing advance in hotter air, so i keep my speeds up higher in hot air

6. then i lost the drive and installed an new style XR and a drive shower - new XR has the finned top cover and dual water pick-ups (MR said it is faster) - New drive kept blowing the prop out when i was trying to get on plane - tried 5 blade prop and still no good - then started trying spacers - 1/2" drive spacer helped a bunch plus I gained top speed - 89.7 mph in 40 degree air but banging the rev limiter to prevent me from getting 90 --

7. sent my ECU to Louisiana and raised the rev limiter - 90mph

[VP]

Originally Posted by tnothin

What was your stock X Dim. and now what is it, how much speed did you pick up.

oh, sorry tnothin --- i do not have the stock X-dimension with me at this time - but i lowered (spaced) the lower 1/2"

The only way to figure all this stuff out is to test it on your boat - they are all different

I will say this though - if you loose any speed when your fuel load lightens up, then your X (drive) is too high

[pullmytrigger]

too high x from the factory.......WOW!

[VP]

That is not as uncommon as you might think according to some. All the mfg'r are looking for more and more speed and push the limit.

In defense of Fountain however, I boosted the power, which if you look at the picture i attached, makes the boat ride even higher up out of the water, running more on its tail - so my guess is that my x-dimension got too high because i increased power and in turn speed.

Make one change and be ready to make 6 more to make everything work properly together again

Take a look at what i went thru (above in this thread) until i finally dialed it all back in again.

[pullmytrigger]

do you think you might gain a bit with the new (lower) style windshield??

[VP]

I have no idea on that but I do not think it would make a whole lot of difference at only 80 - 90 mph

I prefer the higher windshield hands down -- Up here in NY the taller windshield allows me to boat 2 more months of the year in confort - well worth it - would never buy the short one - i also prefer the looks of the tall one

personal prefrence i guess

[PowerboatsNW]

The key to speed in a 575sci boat is air temp! 40 degree air temp is why the boat ran so good! What does the boat run at 90 degree air temp? I love running in the cold to get speed #'s. We ran a stock twin 575sci package in a 36 spectre and got 132 mph at 38 degrees outside. Too bad my wife won't boat with me in snowmobiling weather!

[VP]

Originally Posted by PowerboatsNW

The key to speed in a 575sci boat is air temp! 40 degree air temp is why the boat ran so good! What does the boat run at 90 degree air temp? I love running in the cold to get speed #'s. We ran a stock twin 575sci package in a 36 spectre and got 132 mph at 38 degrees outside. Too bad my wife won't boat with me in snowmobiling weather!

you are 100% correct on the air temp deal - however, after i installed the water injection, i was able to maintain speeds a little better --

We just ran the Pirates Run and ran 86 mph on radar, in 90 degree air, dead calm water, and a 1/2 tank of fuel

[tnothin]

Chambersgc- If you call the factory and give them your hull number they can send you a copy of your test report, if you dont have it, and that will tell you the stock X Dim.

[PowerboatsNW]

Those are impressive speeds and probably a blast to drive! There is nothing like driving a 90mph+ 27-30 ft boat!