louisfever

im interested on raising the x dimension by 2 inches on a scarab 29 ... Engine is a pro charged 502 mpi and was wondering if ill gain any RPMs and MPH ... ??????????? Its top speed is 65 mph at 4700 rpm with a bravo 28
Tried a bravo 24 and speed remained the same but at 5300 rpm .....
How much Rpm will it gain by raising the drive 2 inches ??
Need your help ........... Thanks guys

Griff

You will probably see increased prop slip, more rpms without any real mph gain
2" is a big raise without increased hp. It probably won't carry the bow very well.
It sounds like you need a Bravo1 26"

SB

iTrader: (1)

I agree. 26" Should put it in a happier RPM range.

Is something causing all that slip ?
http://www.go-fast.com/Prop_Slip_Calculator.htm

The 28 Bravo had 22% slip.
And the 24 Bravo had 19%.

Do these boat like different props than the Bravo ?

louisfever

Thanks for the input guys .... Ive seen a few with 2 inch shorties here on OSO but thats 5000$ and another grand in shipping and import tax here so i figured its worth raising the engine 2 inches my self and hopefully improve the drivability of the boat and get a some more speed out of her !!!!!
Do you think i wont gain any speed ???????
What prop works best on the 29 scarab ??????

Griff

Read this thread also http://www.offshoreonly.com/forums/p...-hp-500-a.html

tmmii

65 with the Procharger? You might have some other issues. Did one a few years ago, boat ran 62 stock and was bumping 80 after it was all said and done. Off of memory I'm pretty sure it was spinning a 30.

Have you done a compression and leak down test?

louisfever

Tmmii ..... Here in Malta we have alot of current and humidty ... We go down atleast 2 prop pitches compare the usa !!!!! Add to that is that we only have either have 87 or 89 octane fuel .. Nobody knows exactlty what octane we have here haha funny but true !!!!!!! So its not gona perform like the the ones there in the usa because of what i mentioned !!!!!!!
Compression is good also
What props woork well on these boats with standard X Dimension ??????
At the moment it goes 65 @ 4700 with bravo 1 28P and
65 @ 5300 with bravo 24P .....
Would a labbed Bravo 26P increase my Rpm and Speed ???????

louisfever

If I raise the drive will I improve top Speed ????? And if yes by how much ????
I appritiate your help guys

Griff

I do not think raising the drive 2 inches will increase top speed on your boat.
I don't think it will carry the bow and the boat will run too flat and too wet causing more drag.

louisfever

Thanks Griff for the advise ... The best thing to do i think is prop the boat @ 5000-5100 Rpm and leave the way it is .... I Love speed but im not in a position to buy a big motor and drive at the moment ...