Redeye

Hello every one, I recently purchased a 500 EFI thru the Offshore Only classifieds and am almost done with the install into my Cougar 20.5 sport skier.

We are changing the stock bravo 1.50 gears to the 1.35 to one and I am wanting prop suggestions from the experts here
Also if any others have gone this route or equal horsepower
(470) in thier cougar what prop did you run and what speeds did you achieve.

I was running 62 mph with the stock gears and the 310 hp 454

Thanks for reading

A.O. Razor

Welcome to OSO. A good idea could be to do a base line test with your old prop and the new gear ratio. Also, oitch make/model of the old prop, ect. Speed @ ??? rpm is usefull for the best help. Is the 62 mph GPS speed?

Good luck with the project. Should be a fun boat

Redeye

Thanks for the input I was using a 23p mirage prop and the speed was on speedo only

A.O. Razor

Ok. Did you like how the Mirage worked?

Your actual speed is somewhat lower than your pitot speed. 55 to 58 I would say.

If you use the 23 and have a slip of 14% or so, then you would see about 73 @ 5200 rpm. This engine will rev a little higher than that though, if needed. You might not need a different prop.

I would bolt the Mirage wheel on and try, it won't be far off. If it seems a bit low, get it labbed to a higher pitch, or v.v. if to tall. Bblades is a good place to go.

2Slow4me

Great set up, I'm curious how it will perform.

I have a very similar boat an Eliminator 20'7" 207 Skier with a 454 Magnum.

The one thing I did that make a drastic improvement, raised the drive 3", day and night.

So measure your X dimension (height of prop shaft or cavitaion plate relative to bottom of boat, I forgot which one)

For speed cavitaion plate should be at least a couple of inches above the boat, but the factory mounts very low.

I was running a 3 blade 25" mirage, and now a 4 blade Bravo 28" and could probably turn a 30" lab. Tried others, but the Bravo had better mid speed, better take off, and MUCH better turing, no caviation at all (other did cavitate)

IMCO has the shorty drives to raise the drive, of a stand off box would work, but its rare to see one on a small boat. One guy I have seen on here put it on e Chris Craft 222 Stinger, but not sure of the results.

Redeye

thanks guys for your input,
Changing the gears and running the 23 mirage to get a baseline was also the advice of my mechanic buddy that is helping me with the install we wanted to try not to spend the big bucks that the big props require.
We have tried several props on the 454 and the 23 mirage was definately the winner for overal performance and handling.
As soon as we hit the water I will get back with results.

iCajun

I'm doing a similar conversion on my sport skier, still getting all the parts together and waiting to get the boat out of winter storage. I have the stock 4-blade 24P prop, good for skiing but seems to be underpropped for any top end runs. Are you using the 500EFI injection controller and cool-fuel setup? I'm looking into the Megasquirt controller and adding an in tank fuel pump similar to the Mastercraft setup.
Thanks,
Alan

Sledge Hammer

I am wondering why you are changing the gears? The 1.5s should work fine. A prop will cost you less than the gears and is a lot easier. A 25 or 27 mirage + would be about right with a deep drive setting. The Bravo will be more stable and will be needed if you raise the drive. I would try the drive as is before I went with gears. You can usually try befor you buy a prop.

Redeye

I am going with the gear change on the advice of my (mercruiser certified) mechanic he is very familiar with my boat and has done many performance builds. He also had the gears at home and is doing the work at the good buddy rate! If he is wrong he will change them back for be no problem no charge. I will share your thoughts and we will consider all options.
Thanks for your help

Redeye

Hi Alan
We are using the stock 500 efi setup (less E tops) they wont fit under the hatch or clear the transom........ how frustrating was that!
We went with the imco power flow exhaust and will be giving it side exit tips from corsa. they should be here thursday. I am a little nervous about drilling a 4" hole in the sides of my boat but we will get it done.
let me know how your comes out!