Sport 280

Keep us posted on the outcome. The older 357s are cool boats. Takes a lot of power to move the heavy deep v bottoms.

Just as a side note, I have an 89 28 Baja Sport with 540 horse 502s. It is also a heavy boat. Still working on props, but have run 79.1 gps with stock Bravo I 26 pitch four blades. I am very careful on the sticks and keep the boat from jumping out of the water, hoping my bravo drives will last a while.

rob vanharten

I will let you know what she is running when I get it buttoned up, and in the water.

JimJ

Does anyone have any information on the slip calculation or performance differences between 2 - 3 - 4 -5 blade props? I am sure there are thousands of different senarios but I have been told that 4 blades will come out of the hole faster but 3 blade will have a higher top speed.

Sport 280

I am no prop expert by any means but when I had 400 horse 454s, best top was 68 with 23 pluses turning in. Put 24, Bravo I turning in and best top was 66. With the 24 Bravo I turning out dropped top to 64.8 (all GPS speeds) The 23 pluses turning out topped at 67.4. I did all prop testing on the same day over about a 3 hour period of time.
A lot of differences with props is directly related to drive height. In general, the three blade props work better with deep drives that are stock on older deep Vs. As the drive height is moved up (the centerline of the prop in relation to the bottom of the boat, not trim) then 4 and or 5 blades work better than 3 blades. Also with the drive centerline raised the 4 and 5 blade props have less drag and will produce good top speeds.

When I started with new engines 502s, boat ran 82 mph with 23 pitch pluses, but that was with 6000 rpm tachs pegged, do not know what they were turning, but it was way to much.

I ended up with stock 26 Bravo I props. Boat has run 79.1 GPS at 5250 RPM with 1000 lbs of fuel and people on board. Would likely get another 2-3 mph with labed 27 three blades. But I like the nice mid range cruise and do not like fighting the chine walk at top end.

amazing1

What was your final outcome on your formula?
I am changing my four blades back to three blades 25 pitch and 600 hp. I was curious what you're running?

jrdonnellyjr

How can you find out what your drive ratio is?

BenPerfected

With old school 80's to mid 90's TRS or Bravo drives most/all production boats were all set low X (by 2000+ standards) and Mirage 3-blade props. If you switch to 4-blades Bravo 1's you will decrease your slip and top end and for sure increase you chance to breaking a drive. IMO, will will gain little besides a little better cruise MPH while significantly increasing the chance of of broken drive...ain't worth it.
Ben

glassdave

iTrader: (1)

when i redid the transom on my 89 Scarab last year i raised the X dim two inches and did no other mods. Put the motors right back in the same way they came out. Single best thing i ever did to that boat, completely changed the way it carried and rode. I maybe picked up a mile an hour on the big end but the cruise went up considerably (8-10mph or so). Well worth the effort, I am sure most of it came from switching to a four blade but having it in the right location helps tremendously. Wish i would have tried the B1's before i did the X raise just to see. My boat was a slug with the Mirage props, now when i hit the trim it actually translates directly to the ride attitude.

rfgonzo

I'll tell you in 8 days when you show up for the run!!!!! And we see how fast you go!!!