Topgun non step props?
 

looking for prop suggestions:

1999 topgun kevlar hull
no step
notched transom
555ci motors NA, according to dyno sheets:
748hp at 6100 Rpms
peak torque is 652 ft/lbat 5700 but starting at 4100 it’s 630ft/lb
bravo xr drives max machine internals 1.5 ratio

I read a post here from long ago of similar boat running 30p

Im running Stock bravo 28s and can’t get them much over 5000rpm

not looking to set any speed records but want to get the most out of my setup.

I ran those props on a 93 TG with 500 EFI's and spun them 5100 ...how deep are the drives

Gonna have to measure them buy they’re standard Xr lowers w nosecones

I almost think I need to go down to 26s to get some more Rpms out, but seeing the other posts has me confused.

Should I be running smaller props faster or bigger props slower?

were you at the dyno sessions , you sure their making 750 hp.....what speed are you running

Something is not right for sure and I doubt its the props. You should be able spin the 28's much higher than 5000rpms with 750hp a side. The dyno numbers you said show plenty of torque above 4100 rpms, so its not like you have a lack of torque and need to spin them up to get over an rpm hump.
What GPS speeds are you seeing at WOT???

Best so far is 72 on gps

I was not at the dyno sessions, I just have the reports from when these motors were built by previous owner.

The motors aren’t making 750. They’re making 550 at best.

i was going to say my warmed-up hawk 525's that we estimate are doing 550-575hp had me @ 72 mph top speed.

That would explain why something not adding up ...the dyno sheet shows 598 at 5000rpm

i just can’t get past that with these props

Looking at a dyno sheet from the Cig that shows 977.1 TQ/1060.5 HP at 5700. At 6100 shows 948.5 TQ and 1101.6 HP. Actually at 6300 shows 924.5 TQ and 1108.9 HP. From 5000 to 6000 HP went up 100. So based on these it is feasible. We had 911 HP at 4500. ??

my 87 no step no notch boat with 650s on sweptback xrs regular lowers turn 5 blade 28s 5600 at 80mph.

that sounds closer to me...+\- 600rpm, 8mph.

what kind of 5 blade do you have?
what are your slip #s?

damn!

https://cimg8.ibsrv.net/gimg/www.off...e8fd6373e.jpeg
This is what I have for mine

p5x hydromotives. I average 78mph landed full of fuel on slack tides. But run light I’ve seen 82 all on gps. I think my slip numbers are a little high. But never really put much into it. I’m swapping over to imcos so I’m gonna start the prop shuffle lol.

So the engines were built and dynoed 5+ years ago???
Did you have them built?? How many hours on them?? What is timing set at and do you know what it was set at when dynoed??

yes, but done by previous owner. Not sure what they were timed at before, but I have them base at 24* and if I remember right 34* at 3000rpm

only a hundred hours or so on the motors, boat sat for awhile before I bought it.

if you sell the props keep me in mind I’d be interested to try them

they will be for sale in about 3 weeks.

I have a 1990 straight bottom had stock 575 sci and Konrad 540s boat spun 30p 4 blade to 5200 for best of 79.6 and 28 5 blades at 5150 got 80.8 so something seems off with engines unless drives are super deep

If your having trouble spinning a 4 blade 28 more than 5k a five blade 28 won’t be the answer it will help your cruise but not top you need more rpm try a 5 blade 26p b1 prop that should get you decent cruise and a bit more top

where are the drives trimmed to when trying to get max speed, are you trimming them out as the boat comes on plane

Also something to think about is xrs on a straight bottom and bigger power might wasn’t to stay with a 4 blade I may have some 26p 4 blade off my old bullet you can try

mostly cruise anyway, top speed just for grins now and then. I am thinking 26 might be the answer.

sure let me know !

last time I went for top speed had the drives at “4” on the indicator

going to mark my indicators at neutral and above neutral for reference.

I’ll look this weekend when I’m at the shop working on the old girl

probably a conversation for other thread but quickly what’s the difference between hydros and bravos for these heavy flat bottoms?

A standard flat bottom seems to really like 4 blade b1 props my boat has been re rigged with a higher x so it likes 5 blade props a lot I haven’t had much luck with hydros on the cigs but seems some people do.

Makes sense I hadn’t seen much about hydros for flat bottoms. Interesting to hear someone has had good luck though

Are you trimming it out?

you should rev them 28's to 6000 with that hp, buddy's 500efi boat does 72&5200 you either are not trimming or engines are not even close to the hp, what are specs on engines?

my 91 Konrad gun with 600's and 28's did 72@5100 (needed 26's) saw 75@5300 with those

Got any uncorrected Dyno numbers?

What is your exhaust setup compared to the Dyno? 750hp is a stout a 555. Big cam and good exhaust required