Why is it so slow?
 

Finally got my Slingshot to Europe, but a little disappointed by the performance, she maxed out at 87 on the GPS. Running 575sci/bravo xr 32p bravo props turning 5600rpm, with smaller s/c pulley and reflashed ecm supposedly making 630 hp.
I thought the boat shpuld make 95. Any suggestions???

Fred

which one is it ?
and how many hours on the motors?
the 575's usually need a refresh topend at 300 hours or so depending on how it was used

Boat was named Just Push Play and Throttle therapy.

Had new valve springs last year and i just did valve job on both motors. All compessions are good.

I may be wrong but 32 props at 5600 rpm, 87 gps, not sure about the theorical math of that set up but looks pretty close to reality to me! We often say a 30 pitch is roughly 80 mph, so 32 at 87 I would think it's good!

No?

Sounds like i need bigger props, 5600 rpm is rpm limit, maybe 36p bravos?

the factory 500efis was 5250rpm and 30inch 1.50 gear speed varied between 85-86, that was the factory test reports,

My factory test sheet showed 86.9. most 388's ive seen and driven are a 85mph

at 750 hp around 5900 was 99 w/ 28's 1.30 gear ratio


What options and and altitude?

May be past peek HP RPM wise

What speed was claimed when you bought it?

Hi Strip, boat is at sea level, ambient temp 25c and of course i was told mid 90 s! However the tattle tale on the GPS does say 92 but i dont think i would see that with the current setup, maybe the boat has had different props on.
I know from reading the posts on this site that you are extremely knowledgeable when it comes to the slingshot as you have successfully increased the performance of your boat. I do think i may be close if not on the limiters (5600) so perhaps a bigger prop? Do you think 36 Bravo would get me there or do i need to look at something special like Herrings or labbed props?
Fred

i believe the guy who owed it (just push play) had purchased a set of Herrings for it,
I knew the people that owned it before him(throttle therapy) and the best he saw was 97 but it would run 92-93 regularly, and he rarely ran it hard and took excellent care of it.

Fred I am running stock merc 4 bl bravos, ck the props and see if theve been reworked, ya never know what someone els put on it?

As far as 5 bl maximus or herrings 5-6 blade I belive it will have to much stearn lift, and could throw it into a bad chine walk

Most drive settings are at 2.5 to 3. & tabs up at wfo

I usally run a 30pt 59-6000rpm w/ a 1.30, I tried a set of 32 it was getting up on the props,pretty hairy,still ran a 102.1.they need to be labed to get less stearn lift. Really dont thimk anything is left in mine,unless ya sart throwing money and unlimited testing.
Does it have a blower? if so whats the boost presure?

I like buzzing a motor, try a set of 34's, I was told the bigger diamiter like 36 and above wasent as efeciant as 28-32 in a bravo one pump

Do you have any info on the motor were peek HP might be???

also remenber be easy on the bravo drives:drink:

Rob:ernaehrung004:

Thanks MWDILL, that sounds like a familiar story. I was told that Herrings (borrowed) had been tried and given 97 mph but i thought it was just sales talk!

Rob,I bought the boat and it had blown both head gaskets on the port motor, the previous owner had fitted a boost kit from Arizona speed and Marine upping the boost on the 575 sci to 6 / 6.5 psi and increasing the rev limit to 5600 from 5200 adding 80 hp per motor (630 at the prop). I guess that the peak power is probably around 5200 and i should try props but which type??

Fred

I have a pair of Bravo 1 34's lab finished by Mercury in excellent condition, only used several times, that I would sell to you?

Give me a call or email.
714-822-6045
[email protected]

MWDILL, When it was Throttle Therapy do you know what props it had?

Fred

i believe 32 bravos, worked but not sure by who, i have his phone number, he can tell you all about it and what he did to it and what worked for it.

i have Herring 28 5 blades on mine and have a set of bravo 30's that i have yet to try, the cruise with the Herrings is just too nice :D:

Thanks,
My email [email protected]

Fred

Throttle Therapy
 

I also know the owner of the boat when it was Throttle Therapy. It had a set of 32 bravo's. The boat ran in the 90's, it never had a gps on it though. I spoke also to the person they sold it to and he also said it ran high nineties with the Herring's. I can't believe that, a new owner of a 388 w/ Herring's and no driving experience in that boat like Strip said it would be a huge handful. My 388 ran 100+ w/ 32 bravo's from b blades and it was a huge handful above ninety five or so. It took me a while to get used to the chine walking. When I spoke to the guy about driving the boat he had no clue. Your boat should be running faster depending on the altitude and the shape of the props. If it still has the props I remember, they could definitely use some work, they were pretty whipped. The people that owned it that I knew were meticulous about the boat. The boat is beautiful. Good Luck

You must have a 1.50 gear? I allways wondered what my boat would do with 5 blade Herrings:drink:Ive been trying to find a set of the Maxumus 5bl 28's.Iam afraid of the stress it would put on the drives.

strip
 

Throttle Therapy had 1.50 gears. I had the b max ht's, what a joke, the guy that bought my boat has already had them apart twice. The gearsets had hairline cracking in them and he tried to get parts from Dean under warranty and was told he didn't have the parts. He didn't want any labor, just parts. I think all the 500 efi 388's had 1.50's.

Hey Don!
hows the coastal life :drink:
maybe you have Toms email so he can reach him.
tell your little lady Lori and i said hey!

yes, 1.50's , getting on plane can be tricky sometimes depending on the load. but im getting familar with it, they also seem to like 2.5 on the trim

Whats up,ya missing that Hustler?
bet ya been fishing a lot:ernaehrung004:

Hey Strip
 

I miss the noise and power, but not the empty wallet and maintainence. I out over a hundred hours on the new boat in a year and a half and have done nothing but put gas in it. I don't fish at all, only thing we catch is a buzz:ernaehrung004:. Went out yesterday and got caught in a nasty storm 4's and 5's for about 10 miles. I wish we could of had some pictures of that. I think we were aired out more than in the water. The boat handles it amazingly well once you figure out the water. How's your boat doing? Tried anything new?

Keep in touch, you going to Key West for the World's? If you are we can hook up:ernaehrung004:

Will
 

What's up Will, how's that new boat treating you? Looks awesome, keep it stock or you know the saying " your a __ck" I don't have Tom's email but I can get it. All is well down here. We do quite a bit of boating when the weather permits. This year we have got alot of rain on the weekends. We have only got out twice in the last four weeks. Were going to camp out this weekend and got nailed with storms yesterday and had to haul ass back in some nasty water. It was a fun ride in, but the rain was pelting us and I didn't have a helmet or goggles.

Jeri says "hey to all" hope you guys are doing well

Keep in touch.

not much, kinda at a wall at 101-102,just riding and taking it easy:drink:

Strip
 

Did you ever upgrade your blocks?

nope, they had a good leak down last winter,one block has extra piston to cycylinder wall clearence, makes it buz higher:rolleyes: so all I did was re polish everything and put them back in,I was told the gen 6 stuff want interchange to the aftermarket blocks,if I could find some good used/new GM blocks id like to start with some fresh std. or 30 over.Really didn't want to buy a rusted out one.Rob:ernaehrung004:

Speed sounds about right to me......Mine is dynoed at @ 740+ hp, 1.35 drive ratio on Stelling boxes in the neutral pos., and spinning a set of worked over bravo 30's..........97.4 GPS. Want to try a set of Hydromotive P5's in hopes of cutting down on the prop slip. I have a set of stock Bravo 32's that will only turn just over 5000 at 92 mph

don't worry she's staying stock!
Lori loves it , she Say's it's her boat and I'm just her chauffeur :D:
very happy with the fuel consumption, did the Richmond run on 130 gallon, which i thought was pretty good.
have fun! we will keep in touch